Skin & Subcutaneous Tissue

Cutaneous lupus and dermatomyositis skin findings

Clinical Overview and When to Suspect Cutaneous Lupus and Dermatomyositis

— Young to middle-aged woman (F:M ~4:1) with photodistributed rash sparing the nasolabial folds

— Three classic subtypes: acute CLE (malar/butterfly rash), subacute CLE (annular or psoriasiform on shoulders/upper back/V-neck), chronic CLE (discoid scarring plaques, especially scalp/ears/face)

— Constitutional symptoms (arthralgia, fatigue, oral ulcers, alopecia, Raynaud)

— Drug triggers for SCLE: hydrochlorothiazide, terbinafine, TNF inhibitors, PPIs, calcium channel blockers

— Adult with symmetric proximal muscle weakness plus pathognomonic skin: heliotrope rash (violaceous eyelid edema), Gottron papules (knuckles, PIPs, MCPs), shawl sign, V-sign, holster sign, mechanic's hands, periungual telangiectasias with ragged cuticles

— Amyopathic DM: classic skin, no weakness — still requires malignancy and ILD screening

— New-onset dysphagia, dyspnea, or unexplained weight loss raises concern for interstitial lung disease or paraneoplastic DM

Cutaneous lupus erythematosus (CLE) and dermatomyositis (DM) are autoimmune photosensitive dermatoses that frequently appear on Step 3 as overlap stems blending rheumatology, dermatology, and internal medicine. Both can be skin-limited or systemic, and both demand a workup for organ involvement and, in DM, occult malignancy.

When to suspect CLE:

When to suspect DM:

Board pearl: Adult-onset DM carries a 3–6× increased risk of malignancy within 3 years (ovarian, lung, pancreatic, gastric, colorectal, non-Hodgkin lymphoma, nasopharyngeal in Asian populations). Age-appropriate cancer screening plus CT chest/abdomen/pelvis and pelvic ultrasound are standard at diagnosis and repeated annually for ~3 years.

Step 3 management: When a photodistributed rash is described, ask three questions before ordering labs — Is it scarring? Does it spare the nasolabial folds? Is there muscle weakness? Scarring discoid plaques → CCLE; nasolabial sparing + malar → ACLE; weakness + Gottron → DM.

Presentation Patterns and Key History

— Malar "butterfly" erythema, sparing nasolabial folds, often after sun exposure

— Strongly linked to systemic SLE (≥50% have SLE)

— May be generalized maculopapular eruption mimicking drug rash

— Annular polycyclic or papulosquamous (psoriasiform) plaques on sun-exposed upper trunk, extensor arms, V of neck — spares the face and below the waist

— Non-scarring but leaves dyspigmentation

— ~50% meet SLE criteria, but severe organ disease is uncommon

— Anti-Ro/SSA positive in ~70%; ask about neonatal lupus in offspring (congenital heart block)

— Always elicit drug history within 4–8 weeks (HCTZ, terbinafine, PPIs, TNFα inhibitors, ACEi, statins)

— Coin-shaped, indurated, hyperkeratotic plaques with follicular plugging, atrophic scarring, dyspigmentation, scarring alopecia

— Localized (above neck) has low SLE risk; generalized DLE (above and below neck) carries higher systemic risk

— Long-standing DLE plaques can transform into squamous cell carcinoma, especially on lip/scalp

— Insidious symmetric proximal weakness — difficulty rising from chair, combing hair, climbing stairs

— Skin often precedes weakness by weeks to months

— Ask about dysphagia (cricopharyngeal weakness → aspiration risk), dyspnea/cough (ILD, especially with anti-MDA5, anti-Jo-1), arthralgia, Raynaud, weight loss/B symptoms (malignancy)

— Juvenile DM: add calcinosis cutis, vasculopathy, lipodystrophy; no increased malignancy risk in children

Acute CLE (ACLE):

Subacute CLE (SCLE):

Chronic CLE / Discoid lupus (DLE):

Dermatomyositis:

Key distinction: Malar rash of lupus spares the nasolabial folds; rosacea and seborrheic dermatitis involve them. Heliotrope rash crosses the eyelids and is often accompanied by periorbital edema — a subtle finding sometimes mistaken for allergic contact dermatitis or angioedema.

Board pearl: Pruritus is prominent in DM ("the itchy myositis") but minimal in CLE — itch on the scalp with burning is a soft DM clue.

Physical Exam Findings and Functional Assessment

— ACLE: confluent malar erythema, often edematous, spares nasolabial folds, may extend to forehead/chin; photodistributed maculopapular rash on chest/arms

— SCLE: symmetric annular lesions with central clearing and raised erythematous border, or psoriasiform scaly plaques; photodistribution highly characteristic

— DLE: indurated disk-shaped plaques; carpet-tack sign (keratotic spikes on undersurface of removed scale); central atrophy, telangiectasia, dyspigmentation, scarring alopecia on scalp; conchal bowl involvement classic

— Lupus profundus/panniculitis: firm subcutaneous nodules with overlying skin changes, often on proximal extremities/face → lipoatrophic depressions

— Chilblain lupus, lupus tumidus (urticarial plaques without scale)

— Oral/nasal ulcers (typically painless), nonscarring diffuse alopecia, periungual erythema

— Heliotrope rash: violaceous eyelid discoloration ± periorbital edema

— Gottron papules: violaceous, flat-topped papules over MCP, PIP, DIP, elbows, knees (not the phalanges between joints — that helps distinguish from lupus, which spares knuckles and hits the phalanges)

— Shawl sign (posterior shoulders/upper back), V-sign (anterior chest), holster sign (lateral thigh)

— Mechanic's hands: hyperkeratotic, fissured lateral fingers — antisynthetase clue

— Periungual telangiectasias, dilated nailfold capillary loops, ragged cuticles (Samitz sign)

— Calcinosis cutis (especially juvenile DM)

— Anti-MDA5: cutaneous ulcers over Gottron sites, palmar papules, rapidly progressive ILD

— Manual muscle testing of deltoids, hip flexors; 30-second sit-to-stand is a quick bedside metric

— Assess swallow (water swallow test), neck flexor strength (head lag supine), and respiratory effort

Cutaneous lupus exam:

Dermatomyositis exam:

Functional/strength testing:

Step 3 management: Bedside swallow screen + pulse oximetry on room air at initial DM visit — a desaturation or dysphagia trigger urgent admission for aspiration risk and ILD workup.

Diagnostic Workup — Initial Labs, Serologies, and Imaging

— CBC (cytopenias), CMP (Cr, LFTs), urinalysis with microscopy (proteinuria, casts → lupus nephritis screen), spot urine protein:creatinine

— ANA by IFA (sensitive >95%); if positive, reflex to anti-dsDNA, anti-Smith, anti-Ro/SSA, anti-La/SSB, anti-RNP, antiphospholipid panel (lupus anticoagulant, anti-cardiolipin, anti-β2GP1)

— Complements C3/C4 (low in active SLE), CRP/ESR

— Direct Coombs if anemia

— CK (often elevated 5–50× ULN; may be normal in amyopathic DM or late disease), aldolase, AST/ALT (muscle source), LDH

— TSH (rule out hypothyroid myopathy), CMP, CBC

— Myositis-specific antibodies (MSAs): anti-Mi-2 (classic skin, good prognosis), anti-MDA5 (amyopathic, rapidly progressive ILD, skin ulcers), anti-TIF1-γ and anti-NXP2 (strongest malignancy association in adults), anti-Jo-1 and other antisynthetases (antisynthetase syndrome: ILD, mechanic's hands, arthritis, Raynaud, fever)

— Myositis-associated antibodies: anti-Ro52, anti-PM/Scl, anti-U1RNP

— CXR baseline; HRCT chest if any dyspnea, cough, crackles, low SpO2, or anti-synthetase/MDA5 antibody

— PFTs with DLCO at baseline in DM

— MRI of proximal muscles (thigh STIR) identifies edema, guides biopsy site, distinguishes active inflammation from chronic damage

— CT chest/abdomen/pelvis, mammogram, Pap, colonoscopy (age-appropriate), pelvic/transvaginal ultrasound + CA-125 in women, PSA in men, nasopharyngeal exam in high-risk ethnicities

— Repeat screening annually for ~3 years post-diagnosis

Initial labs for suspected CLE/SLE:

Initial labs for suspected DM:

Imaging:

Malignancy screen at DM diagnosis (adults):

Board pearl: Anti-TIF1-γ positivity in a patient >40 confers up to ~50% risk of underlying malignancy — pursue exhaustive screening, including PET/CT if standard imaging negative.

Key distinction: SCLE = anti-Ro; antisynthetase = anti-Jo-1; rapidly progressive ILD with amyopathic skin = anti-MDA5.

Diagnostic Workup — Confirmatory Studies and Biopsy

— 4-mm punch biopsy of an active, untreated lesion (edge for DLE; non-sun-exposed for direct immunofluorescence if needed)

— CLE histology: interface dermatitis with vacuolar change at the dermoepidermal junction, perivascular/periadnexal lymphocytic infiltrate, increased dermal mucin; DLE adds follicular plugging, basement membrane thickening, scarring

— DM histology: vacuolar interface dermatitis with epidermal atrophy and dermal mucin — histologically near-identical to CLE; clinical context distinguishes

— Lupus band test (DIF): granular IgG/IgM/C3 at DEJ in lesional skin (CLE) or non-lesional sun-protected skin (SLE)

— Site guided by MRI to avoid sampling error

— Perifascicular atrophy, perimysial inflammation (CD4+ T cells, B cells, plasmacytoid dendritic cells), MAC deposition on capillaries, capillary dropout

— Distinguishes DM from polymyositis (endomysial CD8+ infiltrate invading non-necrotic fibers) and inclusion body myositis (rimmed vacuoles, older men, finger flexor and quadriceps weakness, treatment-resistant)

— Biopsy can be deferred if classic skin + characteristic MSA + proximal weakness + elevated CK are all present (EULAR/ACR 2017 criteria)

— Myopathic pattern: small-amplitude, short-duration polyphasic motor unit potentials, fibrillations, positive sharp waves, complex repetitive discharges

— Helps distinguish neurogenic vs myopathic and guides biopsy contralaterally

— Echocardiogram if anti-synthetase/MDA5 (pulmonary hypertension, myocarditis screen)

— Cardiac MRI or troponin if chest pain or arrhythmia in DM (myocarditis)

— Swallow study (videofluoroscopy) in dysphagia

Skin biopsy:

Muscle biopsy for DM (gold standard when diagnosis uncertain or rapidly progressive):

EMG/NCS:

Additional confirmatory testing:

CCS pearl: When ordering a skin biopsy on CCS for suspected CLE, sequence: dermatology consult → punch biopsy (lesional) → DIF on perilesional skin → ANA/ENA panel while results pending. Don't start hydroxychloroquine until biopsy obtained if diagnosis is genuinely uncertain — steroids and HCQ can blunt histology.

Risk Stratification and First-Line Management Logic

— Subtype (ACLE/SCLE often signal systemic; DLE often skin-limited)

— Extent (localized vs generalized — generalized DLE has ~28% systemic conversion risk)

— Scarring potential (DLE on scalp → permanent alopecia → aggressive early therapy)

— Systemic involvement (renal, hematologic, CNS, serositis on ACR/SLICC/EULAR criteria)

— Muscle involvement severity (CK, swallow, respiratory muscle strength)

— ILD presence/progression (HRCT, DLCO, anti-MDA5/Jo-1)

— Malignancy association (anti-TIF1-γ, NXP2, age >40)

— Cardiac involvement (myocarditis, conduction disease)

— Functional impact (manual muscle testing, dysphagia)

— Strict photoprotection: broad-spectrum sunscreen SPF ≥30 (preferably mineral with zinc/titanium, SPF 50+ recommended), reapplied q2h; wide-brim hat; UPF clothing; window film; avoidance of midday sun

— Smoking cessation: smoking worsens disease and reduces hydroxychloroquine efficacy

— Vitamin D supplementation (photoprotection limits synthesis)

— Review and remove offending drugs in SCLE (HCTZ, terbinafine, PPIs, TNFi, CCBs)

— Vaccinations updated before immunosuppression: pneumococcal, influenza, COVID, shingles (Shingrix), HPV; avoid live vaccines once on immunosuppression

— Topical/intralesional → antimalarials → systemic immunomodulators → biologics

— DM: corticosteroids early + steroid-sparing agent from the outset (don't delay)

Stratify CLE by:

Stratify DM by:

Universal foundational interventions (both diseases):

Treatment ladder principle:

Step 3 management: Any new SCLE diagnosis triggers a medication reconciliation — discontinue suspected culprit and recheck skin in 4–8 weeks before committing to long-term immunosuppression. ~30% of SCLE is drug-induced.

Board pearl: Hydroxychloroquine is foundational for nearly all CLE patients regardless of subtype — it reduces flares, organ damage, thrombosis risk, and mortality in SLE.

Pharmacotherapy — First-Line Drug Regimens

— High-potency topical corticosteroids (clobetasol 0.05%) BID for 2–4 weeks on body; mid-potency on face for limited duration

— Topical calcineurin inhibitors (tacrolimus 0.1%, pimecrolimus 1%) — facial/intertriginous, steroid-sparing

— Intralesional triamcinolone 5–10 mg/mL for refractory DLE plaques

— Hydroxychloroquine (HCQ) 5 mg/kg/day actual body weight (max ~400 mg/day) — onset 8–12 weeks

— Add quinacrine if partial response; switch to chloroquine rarely (higher retinal toxicity)

— Baseline ophthalmology exam within first year, then annual screening after 5 years (OCT, visual fields) — risk of irreversible bull's-eye maculopathy rises with duration and dose

— Check G6PD if Mediterranean/African descent (hemolysis risk modest but worth screening)

— Smoking reduces HCQ efficacy — counsel cessation

— DM first-line: prednisone 1 mg/kg/day (up to 60–80 mg) for 4–6 weeks, then taper over 9–12 months

— Pulse IV methylprednisolone 1 g × 3 days for severe weakness, dysphagia, myocarditis, or rapidly progressive ILD

— Bone protection: calcium, vitamin D, bisphosphonate if prolonged ≥7.5 mg/day; PJP prophylaxis (TMP-SMX) if prednisone ≥20 mg ≥4 weeks plus another immunosuppressant

— Methotrexate 15–25 mg weekly + folic acid (avoid in ILD — pneumonitis risk)

— Azathioprine 1–2 mg/kg/day (check TPMT/NUDT15 first)

— Mycophenolate mofetil 2–3 g/day — preferred when ILD present

— IVIG 2 g/kg/month — refractory DM, dysphagia, pregnancy-compatible; FDA-approved for DM (octagam)

— Rituximab for refractory disease; JAK inhibitors (tofacitinib) emerging for MDA5-ILD and refractory skin DM

Topical therapy (CLE first line, DM skin adjunct):

Antimalarials (cornerstone of CLE, adjunct in DM skin):

Systemic corticosteroids:

Steroid-sparing agents (start early in DM, refractory CLE):

CCS pearl: Pair every prednisone start with calcium 1200 mg, vitamin D 800–1000 IU, PPI if GI risk, bone density baseline, and glucose monitoring — checking these boxes shows up on CCS scoring rubrics.

Refractory Disease and Expanded Pharmacology

— Inadequate response to HCQ + topicals after 3 months → add quinacrine or switch to methotrexate 15–25 mg weekly or mycophenolate 2–3 g/day

— Next: belimumab (anti-BLyS) — FDA-approved for SLE including cutaneous disease

— Anifrolumab (anti–type I interferon receptor) — strong efficacy for skin manifestations in moderate-severe SLE

— Dapsone especially for bullous SLE and urticarial vasculitis (check G6PD first)

— Thalidomide/lenalidomide for refractory DLE (severe teratogen — REMS program, contraception, neuropathy monitoring)

— Rituximab, cyclophosphamide for severe systemic disease

— Add second-line immunosuppressant if not on one

— IVIG 2 g/kg/month — particularly effective for dysphagia, skin, and weakness

— Rituximab 1 g × 2 doses (RIM trial supports use)

— Cyclophosphamide for severe ILD or vasculopathy

— JAK inhibitors (tofacitinib, baricitinib) for refractory skin DM and MDA5-associated rapidly progressive ILD — emerging evidence

— Calcinosis cutis: no proven therapy; trials of bisphosphonates, diltiazem, sodium thiosulfate, surgical excision for symptomatic deposits

— Triple therapy early: high-dose glucocorticoids + calcineurin inhibitor (tacrolimus) + cyclophosphamide or rituximab; plasma exchange in refractory cases

— High mortality — early aggressive treatment within weeks of diagnosis

— Mycophenolate or azathioprine + steroids; rituximab if progressive

— Avoid methotrexate (pneumonitis risk confounds picture)

— Stop the offending drug → resolution typically in 6–12 weeks; short course topical/systemic steroids and HCQ as bridge

Refractory cutaneous lupus pathway:

Refractory DM pathway:

MDA5+ rapidly progressive ILD:

Antisynthetase syndrome ILD:

Drug-induced SCLE management:

Board pearl: Anifrolumab and belimumab are the two FDA-approved biologics for SLE skin; IVIG (octagam) is the FDA-approved biologic for DM. Memorize these — high-yield Step 3 trivia.

Step 3 management: Before starting any immunosuppressant, screen for latent TB (IGRA), HBV, HCV, HIV, and update vaccines — these orders should be reflexive on CCS cases.

Special Populations — Elderly, Renal, and Hepatic Impairment

— New-onset DM after age 40 → aggressive malignancy screen including CT C/A/P, age-appropriate screens, and consider PET/CT if conventional imaging negative and anti-TIF1-γ positive

— Polypharmacy raises drug-induced SCLE risk — review thiazides, CCBs, PPIs, statins, terbinafine, TNFi

— Steroid-induced complications magnified: osteoporosis, diabetes, cataract, infection, delirium — taper aggressively, use steroid-sparing agents earlier

— Methotrexate clearance falls with renal function — dose-adjust and monitor

— Methotrexate contraindicated when CrCl <30 mL/min; reduce dose if CrCl 30–60

— Mycophenolate safe in renal disease but watch GI/cytopenias

— HCQ dose by actual body weight (5 mg/kg) — does not require renal adjustment, but accumulates in long-standing disease; monitor closely

— NSAIDs avoided in lupus nephritis or CKD

— Cyclophosphamide dose-adjust for CrCl; hydration and mesna mandatory; bladder cancer surveillance

— Active lupus nephritis: induction with mycophenolate or cyclophosphamide + steroids; consider voclosporin or belimumab add-on (per KDIGO 2024 guidance)

— Methotrexate hepatotoxic — avoid in cirrhosis, heavy alcohol use, NAFLD with fibrosis; baseline and periodic LFTs, consider FibroScan

— Azathioprine hepatotoxic and myelosuppressive — check TPMT/NUDT15, monitor CBC/LFTs

— Hydroxychloroquine safe in liver disease

— Avoid live vaccines in immunosuppressed patients

— Falls risk from steroid myopathy + DM weakness — early PT/OT referral, home safety, swallow eval

— Goals-of-care discussions for elderly with rapidly progressive MDA5-ILD

Elderly considerations:

Renal impairment:

Hepatic impairment:

Frailty:

Step 3 management: In a 68-year-old with new heliotrope rash and Gottron papules, the first 3 outpatient orders should be: CK + MSA panel, HRCT chest with PFTs, and age-appropriate cancer screen + CT C/A/P — the malignancy hunt is non-negotiable.

Board pearl: Bull's-eye maculopathy risk from HCQ rises sharply after 5 years cumulative use or doses >5 mg/kg/day — adjust in renal disease where the drug accumulates.

Special Populations — Pregnancy, Pediatrics, and Demographic Subgroups

— Preconception counseling: disease quiescent for ≥6 months before conception; off teratogens; baseline labs (anti-Ro/La, antiphospholipid, complements, urine protein)

— Anti-Ro/SSA + anti-La/SSB cross the placenta after 16 weeks → neonatal lupus (transient rash, cytopenias) and congenital complete heart block (irreversible, 2% first pregnancy, 18% recurrence) — fetal echo weekly 16–26 weeks

— Continue HCQ throughout pregnancy — reduces flares, neonatal lupus, congenital heart block

— Low-dose aspirin from 12 weeks reduces preeclampsia risk

— Antiphospholipid syndrome: prophylactic or therapeutic LMWH per history

— Avoid: methotrexate, mycophenolate (teratogenic — stop 3 months before conception), cyclophosphamide, leflunomide, JAK inhibitors

— Safe: HCQ, azathioprine, low-dose prednisone, tacrolimus, cyclosporine, IVIG, certolizumab; rituximab acceptable preconception/early

— Flare treatment: prednisone <20 mg/day, IVIG

— Rare; outcomes worse with active disease — defer pregnancy until controlled

— Active DM increases fetal loss, prematurity

— IVIG and azathioprine preferred; high-dose steroids if needed

— Peak ages 5–10; calcinosis cutis in up to 40% (especially with treatment delay)

— Vasculopathy drives GI ulceration/perforation, retinal vasculitis

— No increased malignancy risk — skip cancer screen

— Treatment: steroids + methotrexate first-line ± IVIG; aggressive early therapy reduces calcinosis

— Monitor growth, bone health, school functioning

— SLE: Black, Hispanic, Asian women have higher prevalence and severity

— DLE: more common and more disfiguring in patients with darker skin → higher risk of permanent dyspigmentation and scarring alopecia → early aggressive therapy

Pregnancy in CLE/SLE:

Pregnancy in DM:

Juvenile dermatomyositis (JDM):

Demographic patterns:

Key distinction: Anti-Ro+ mother → fetal heart block risk (irreversible structural conduction damage), not neonatal lupus rash alone, which is transient. Weekly fetal echo 16–26 weeks is the screening standard.

Board pearl: Hydroxychloroquine should never be stopped in pregnancy — stopping triggers flares and worsens fetal outcomes.

Complications and Adverse Outcomes

— Permanent scarring alopecia from DLE — irreversible if treated late

— Dyspigmentation (hypo- and hyperpigmentation), especially in skin of color

— Squamous cell carcinoma arising in chronic DLE plaques (lip, scalp) — monitor for nonhealing ulceration or hyperkeratosis

— Progression to SLE: ~5–10% localized DLE, ~20–30% generalized DLE, ≥50% SCLE/ACLE

— Lupus nephritis, neuropsychiatric lupus, hematologic disease, serositis if systemic

— Accelerated atherosclerosis — leading cause of late mortality in SLE

— Antiphospholipid syndrome: venous/arterial thrombosis, recurrent pregnancy loss

— Interstitial lung disease — major cause of mortality, especially anti-MDA5 (rapidly progressive) and antisynthetase ILD

— Aspiration pneumonia from pharyngeal/cricopharyngeal weakness — leading cause of acute mortality

— Myocarditis, conduction disease, heart failure (often subclinical — check troponin, ECG)

— Malignancy — ovarian, lung, GI, lymphoma, nasopharyngeal; risk peaks within 3 years of diagnosis

— Calcinosis cutis — painful, ulcerating, drains chalky material, secondary infection

— Vasculopathy/ulceration (anti-MDA5, juvenile DM)

— Refractory dysphagia requiring PEG tube

— Steroid myopathy confounds the picture — distinguish by normal CK but worsening weakness on high-dose steroids

— HCQ: retinal toxicity (irreversible bull's-eye maculopathy), cardiomyopathy (rare, prolonged use), QT prolongation

— Methotrexate: hepatotoxicity, pneumonitis, cytopenias, mucositis, teratogenicity

— Azathioprine: myelosuppression (TPMT/NUDT15), hepatitis, lymphoma, NMSC

— Mycophenolate: GI, cytopenias, teratogen, infection

— Cyclophosphamide: hemorrhagic cystitis, bladder cancer, infertility, secondary malignancy

— Long-term steroids: osteoporosis, diabetes, cataracts, hypertension, avascular necrosis, infections (PJP, fungi)

Cutaneous lupus complications:

Dermatomyositis complications:

Treatment-related complications:

Board pearl: A DM patient on high-dose prednisone whose weakness worsens but CK is normal/falling has steroid myopathy, not disease flare — reduce steroids and reassess; do not escalate immunosuppression.

When to Escalate Care — Inpatient, ICU, and Consultations

— Dysphagia with aspiration risk — NPO, swallow eval, IV steroids, IVIG

— Respiratory compromise — hypoxemia, dyspnea, new infiltrates → r/o rapidly progressive ILD (anti-MDA5), infection, aspiration

— Severe proximal weakness preventing ADLs/ambulation

— Myocarditis — elevated troponin, arrhythmia, new heart failure

— Suspected myositis crisis with rhabdomyolysis (CK >10,000, AKI risk) — IV fluids, electrolyte management

— First high-dose immunosuppression in unstable patient

— Calcinosis with infection or compartment syndrome

— Systemic flare with organ involvement (renal, neuro, hematologic, serositis)

— Severe drug-induced reaction (TEN/SJS overlap rare)

— Bullous SLE with extensive denudation

— Respiratory failure from ILD or aspiration → high-flow O2, NIPPV, intubation; anti-MDA5 rapidly progressive ILD has mortality >50%

— Diffuse alveolar hemorrhage (SLE) — pulse steroids, plasma exchange, rituximab/cyclophosphamide

— Hemodynamic instability from pericarditis with tamponade, myocarditis

— Catastrophic antiphospholipid syndrome

— Rheumatology — diagnosis, immunosuppression selection

— Dermatology — biopsy, topical regimen, refractory skin

— Pulmonology — ILD management, lung biopsy if needed

— Oncology/primary care — malignancy workup in DM

— Cardiology — myocarditis, conduction abnormalities

— GI/Speech therapy — dysphagia evaluation, PEG decisions

— Ophthalmology — baseline + annual HCQ screening

— Maternal-fetal medicine — pregnancy with anti-Ro+ or APS

— Physical/occupational therapy — strength rehabilitation early

Admit for DM if:

Admit for CLE/SLE if:

ICU triggers:

Consultations:

CCS pearl: For a hospitalized DM patient with new hypoxemia, the sequence is: CXR → HRCT → ABG → blood/sputum cultures → empiric broad-spectrum antibiotics + PJP coverage if on immunosuppression → pulse methylprednisolone if MDA5+ rapidly progressive ILD suspected → pulmonology consult. Don't withhold steroids waiting for cultures in clear autoimmune ILD flare.

Board pearl: Anti-MDA5 + ferritin >1500 ng/mL + falling DLCO is a death-triad for rapidly progressive ILD — escalate immediately.

Key Differentials — Same-Category (Connective Tissue/Autoimmune)

— Raynaud + skin thickening (sclerodactyly, salt-and-pepper dyspigmentation), telangiectasias, calcinosis, esophageal dysmotility

— Anti-Scl-70 (diffuse), anti-centromere (limited/CREST), anti-RNA polymerase III (renal crisis, malignancy association)

— Distinguish from DM: scleroderma lacks Gottron/heliotrope; skin is thickened and bound-down, not violaceous and edematous

— Overlap of SLE/SSc/DM features + anti-U1RNP, often hand swelling ("sausage fingers"), Raynaud, pulmonary hypertension

— Sicca symptoms, parotid enlargement, anti-Ro/La; cutaneous vasculitis (palpable purpura) on legs; overlap with SCLE common

— Proximal weakness without skin findings; endomysial CD8+ infiltrate, MHC-I upregulation

— Now considered rare — many "PM" cases reclassified as IMNM, IBM, or antisynthetase syndrome

— Severe weakness, very high CK (often >10,000), anti-HMGCR (statin-associated) or anti-SRP; minimal inflammation, prominent necrosis on biopsy

— Statin-associated IMNM does not resolve with statin discontinuation — requires immunosuppression

— Men >50, asymmetric finger flexor and quadriceps weakness, dysphagia; CK mildly elevated; rimmed vacuoles on biopsy; poor steroid response — key distinction from DM

— Refer for second opinion if "DM" not responding to steroids in older man

— Anti-Jo-1 (and others: PL-7, PL-12, EJ, OJ); triad of ILD, arthritis, mechanic's hands ± Raynaud, fever; may have DM skin or be purely myositic

— Hydralazine, procainamide, isoniazid, minocycline, anti-TNF; anti-histone antibodies (classic) or anti-dsDNA (anti-TNF–induced); resolves with drug discontinuation

Systemic sclerosis (scleroderma):

Mixed connective tissue disease (MCTD):

Sjögren syndrome:

Polymyositis:

Immune-mediated necrotizing myopathy (IMNM):

Inclusion body myositis (IBM):

Antisynthetase syndrome:

Drug-induced lupus:

Key distinction: Gottron papules and heliotrope are specific to DM; their presence rules out lupus, scleroderma, and IBM as primary diagnosis even if other features overlap.

Key Differentials — Other-Category Mimics

— Centrofacial erythema, papulopustules, telangiectasias — involves nasolabial folds (unlike lupus malar)

— Triggers: heat, alcohol, spicy food; treat with metronidazole/ivermectin topicals, doxycycline

— Greasy yellow scale on nasolabial folds, scalp, eyebrows, retroauricular — distinct distribution from CLE

— Responds to ketoconazole, low-potency steroids

— Pruritic papules/vesicles on sun-exposed skin within hours of UV; resolves spontaneously; lacks systemic features

— Helpful clue: PMLE spares the face (chronically sun-conditioned), affects intermittently exposed sites

— Annular scaly plaque with central clearing — can mimic SCLE; KOH prep positive

— Well-demarcated silvery-scaled plaques on extensor surfaces, scalp, nails (pits, oil drops); biopsy and distribution distinguish from psoriasiform SCLE

— Mimics heliotrope rash — but pruritic, scaly, eczematous, often unilateral, related to cosmetics/nail polish; patch testing helps

— Erythroderma, poikiloderma; biopsy clarifies

— Proximal weakness, elevated CK, no skin findings; TSH normalizes the picture

— Resolves with discontinuation; CK improves within weeks; if no resolution → check anti-HMGCR

— Periorbital edema + myalgia + eosinophilia + raw pork exposure → mimics DM heliotrope

— Chronic, often familial; biopsy and genetic testing distinguish

— Proximal weakness without CK elevation; cushingoid features

Rosacea:

Seborrheic dermatitis:

Polymorphic light eruption (PMLE):

Tinea faciei:

Psoriasis:

Allergic/contact dermatitis (eyelid):

Dermatomyositis vs cutaneous T-cell lymphoma / paraneoplastic dermatoses:

Hypothyroid myopathy:

Statin myopathy (toxic, not IMNM):

Trichinellosis:

Mitochondrial myopathy, muscular dystrophies:

Cushing syndrome / steroid myopathy:

Board pearl: Periorbital edema + myalgia + eosinophilia + recent pork ingestion → trichinellosis, not DM. Check eosinophil count and serology before launching an autoimmune workup.

Key distinction: Nasolabial fold involvement = rosacea/seb derm; nasolabial fold sparing = lupus malar rash. This single anatomic detail separates the two most commonly confused facial eruptions on Step 3.

Secondary Prevention, Discharge Medications, and Long-Term Plan

— Hydroxychloroquine indefinitely — only stop for retinopathy or intolerance

— Topical regimen for flares: clobetasol short courses, tacrolimus for face/maintenance

— Steroid-sparing immunosuppressant (MTX, MMF, AZA) titrated to lowest effective dose

— Vitamin D + calcium; bone density q1–2y if on chronic steroids

— Aspirin 81 mg if antiphospholipid positive (primary prevention) or per cardiovascular risk

— Statin per ASCVD risk — lupus is a CV risk enhancer

— Steroid-sparing agent (MTX, AZA, MMF) usually 2+ years after remission

— Slow prednisone taper over 9–12 months; never stop abruptly

— Topicals for residual skin disease; sun protection lifelong

— IVIG continued in refractory disease

— Strict photoprotection lifelong (SPF 30+, hat, UPF clothing, window film)

— Smoking cessation — improves HCQ response, reduces CV/cancer risk

— Mediterranean diet, exercise, weight management

— Limit alcohol (MTX, AZA hepatotoxicity)

— Annual influenza (inactivated), COVID boosters, pneumococcal PCV20 or PCV15+PPSV23, Shingrix (≥18 if immunocompromised), HPV through age 45 if indicated

— Avoid live vaccines (MMR, varicella, yellow fever, live zoster, LAIV) while immunosuppressed

— Age-appropriate screens + CT C/A/P, mammogram, pelvic US + CA-125, PSA, colonoscopy

— Annually for 3 years post-diagnosis; longer if anti-TIF1-γ or NXP2 positive

— Annual lipid panel, BP, glucose; statin per risk; DEXA if chronic steroids

— Atherosclerosis is the leading late mortality cause in SLE

Maintenance medication regimen (CLE/SLE):

Maintenance regimen (DM):

Lifestyle and risk modification:

Vaccinations:

Cancer screening (DM):

Cardiovascular and bone health:

Step 3 management: At every visit ask "sun, smoke, sleep, stress, meds" — the five modifiable triggers that drive flares. Document HCQ adherence, ophthalmology screening date, vaccine status, and contraception/pregnancy plans.

Board pearl: Mycophenolate and methotrexate require effective contraception and a 3-month washout before conception — counseling and contraception confirmation are testable Step 3 items.

Follow-Up, Monitoring, and Rehabilitation

— Active disease: rheumatology q4–8 weeks until stable

— Stable disease: q3–6 months

— Dermatology: q3–6 months while skin active, then annually

— Primary care: annual comprehensive visit + co-management

— HCQ: baseline ophthalmology, repeat at year 1, then annually after 5 years (OCT, automated visual fields); CBC and LFTs periodically

— Methotrexate: CBC, CMP, LFTs at 2–4 weeks after dose changes, then q8–12 weeks; folic acid daily

— Azathioprine: TPMT/NUDT15 baseline; CBC and LFTs q2 weeks initially, then q1–3 months

— Mycophenolate: CBC, CMP q1–3 months; pregnancy test before initiation and annually

— CK, aldolase quarterly in DM during treatment; combine with strength testing — CK can lag clinical response

— PFTs and HRCT annually (or sooner if symptomatic) in DM with ILD

— Urinalysis + UPCR every 3–6 months in SLE for nephritis surveillance

— Complements C3/C4, anti-dsDNA, CBC every 3–6 months in SLE

— Early physical therapy (gentle ROM initially, progressive resistance once inflammation controlled)

— Occupational therapy for ADL adaptations

— Speech/swallow therapy for dysphagia; videofluoroscopy as needed

— Aerobic exercise has shown benefit; not contraindicated despite historical concerns

— Sun protection technique demonstration

— Smoking cessation referral

— Medication adherence (HCQ daily — easy to forget when feeling well)

— Pregnancy planning, contraception choice (avoid estrogen if APS+)

— Mental health screening — depression common in chronic disfiguring skin disease and chronic illness

— Support groups (Lupus Foundation, Myositis Association)

Follow-up cadence:

Lab monitoring:

Rehabilitation in DM:

Counseling content:

Step 3 management: A patient on HCQ who hasn't seen ophthalmology in 18 months gets referral placed today — overdue retinal screening is a high-yield CCS quality-of-care item.

Board pearl: A rising anti-dsDNA with falling C3/C4 predicts SLE flare weeks before symptoms — monitor in stable patients and tighten follow-up if trending wrong.

Ethical, Legal, and Patient Safety Considerations

— Cumulative cancer risk (azathioprine — lymphoma, NMSC; cyclophosphamide — bladder cancer, AML)

— Infection risk (PJP, reactivation TB, HBV, herpes zoster) — document baseline screening and prophylaxis discussion

— Teratogenicity (MMF, MTX, CYC, leflunomide, thalidomide) — verbal and written counseling, contraception confirmation, pregnancy testing documented

— Thalidomide REMS program: mandatory monthly pregnancy tests, two forms of contraception, registry enrollment

— Hospital discharge after DM flare → high risk of medication errors with tapering steroids, multiple immunosuppressants, PJP prophylaxis. Medication reconciliation with the patient at bedside plus follow-up call within 48–72 hours and rheumatology visit within 1–2 weeks reduces readmissions.

— Patients leaving for surgery: continue HCQ; hold MTX 1–2 weeks if infection risk; stress-dose steroids per adrenal axis status

— Suspected occult malignancy in adult DM requires patient notification and timely workup — failure to pursue cancer screening is a documented malpractice exposure

— Anti-Ro+ pregnant patient must be informed of congenital heart block risk and offered fetal echo monitoring

— Adolescent patients with juvenile DM/CLE: shared decision-making, transition planning to adult care starting at age 14–16, contraception counseling

— Cosmetic disfigurement (DLE scarring alopecia, calcinosis) — psychological impact, screen for depression/suicidality

— Lupus disproportionately affects Black, Hispanic, and Asian women, with worse outcomes tied to delayed diagnosis and access — Step 3 expects awareness of social determinants in care planning

— Sunscreen affordability and access counseling

Informed consent for immunosuppression:

Transitions of care risks:

Mandatory and ethical reporting:

Pediatric considerations:

Health equity:

Patient safety pearl: Always verify a negative pregnancy test before initiating methotrexate, mycophenolate, or cyclophosphamide, and document contraception plan. This is a recurring Step 3 safety/quality-improvement vignette.

Step 3 management: When discharging a patient newly started on prednisone ≥20 mg + steroid-sparing agent, the discharge order set must include: TMP-SMX (PJP prophylaxis), calcium/vitamin D, PPI/GI prophylaxis, glucose monitoring plan, vaccine review, and clear taper schedule with rheumatology follow-up in 1–2 weeks.

High-Yield Associations and Rapid-Fire Clinical Facts

Malar rash spares nasolabial folds; rosacea/seb derm involve them.

Gottron papules sit over knuckles; lupus hand rash spares knuckles and hits phalanges.

SCLE drug triggers: HCTZ, terbinafine, PPIs, TNF inhibitors, CCBs, ACEi, statins.

Anti-Ro/SSA → SCLE, neonatal lupus, congenital heart block; weekly fetal echo 16–26 weeks.

Anti-dsDNA, anti-Sm → SLE specificity; anti-dsDNA correlates with disease activity and nephritis.

Anti-histone → drug-induced lupus (hydralazine, procainamide, isoniazid, minocycline).

Anti-TIF1-γ, anti-NXP2 → malignancy-associated DM in adults.

Anti-MDA5 → amyopathic DM with rapidly progressive ILD, skin ulcers, palmar papules; high mortality.

Anti-Mi-2 → classic skin DM, good prognosis, treatment-responsive.

Anti-Jo-1 (and antisynthetase Abs) → ILD, arthritis, mechanic's hands, Raynaud, fever.

Hydroxychloroquine: bull's-eye maculopathy after >5 years; dose ≤5 mg/kg/day actual weight; annual screening after year 5.

HCQ continued in pregnancy reduces flares and congenital heart block.

JDM features: calcinosis cutis, vasculopathy, no malignancy risk.

DLE → SCC in long-standing scarring plaques (lip, scalp).

Generalized DLE has higher SLE progression risk than localized DLE.

Lupus profundus/panniculitis → lipoatrophic depressions on face/proximal extremities.

Mechanic's hands + ILD + arthritis = antisynthetase syndrome.

DM cancer screen: CT C/A/P + age-appropriate screens + pelvic US + CA-125 annually × 3 years.

Steroid myopathy: normal/falling CK with worsening weakness on prednisone — don't escalate immunosuppression.

PJP prophylaxis: prednisone ≥20 mg ≥4 weeks + second immunosuppressant → TMP-SMX.

Live vaccines contraindicated on biologics/high-dose steroids; give before initiation when possible.

MMF/MTX: stop ≥3 months before conception; HCQ/AZA/tacrolimus pregnancy-compatible.

Anifrolumab (anti–IFNAR) and belimumab (anti-BLyS): FDA-approved biologics for SLE skin.

IVIG (octagam): FDA-approved for adult DM.

Voclosporin: FDA-approved add-on for active lupus nephritis.

Board pearl: Mnemonic for DM skin — "G-HOMVPN": Gottron, Heliotrope, Overlap (mechanic's hands), Malignancy clue (TIF1-γ), V-sign, Periungual telangiectasias, Nailfold ragged cuticles. Reciting this on a stem with photodistributed rash + weakness clinches DM.

Board Question Stem Patterns

— Answer: Drug-induced subacute cutaneous lupus → stop HCTZ, sun protection, topical steroid, consider HCQ; expect resolution in 6–12 weeks.

— Answer: Dermatomyositis → check MSA panel, HRCT chest, PFTs, age-appropriate cancer screen + CT C/A/P + pelvic US + CA-125; start prednisone 1 mg/kg + methotrexate or MMF; ophthalmology referral if HCQ added.

— Answer: Continue HCQ throughout pregnancy, add low-dose aspirin from 12 weeks, weekly fetal echo 16–26 weeks for congenital heart block.

— Answer: Anti-MDA5 rapidly progressive ILD → admit, pulse methylprednisolone + tacrolimus + cyclophosphamide or rituximab; pulmonology and rheumatology consults; consider plasma exchange.

— Answer: Biopsy to rule out SCC arising in chronic DLE; escalate systemic therapy (HCQ + MTX); aggressive sun protection.

— Answer: Steroid myopathy → taper steroids, optimize steroid-sparing agent; do not escalate immunosuppression.

— Answer: Refer ophthalmology now for OCT + visual fields (annual screening after year 5).

— Answer: JDM → steroids + methotrexate ± IVIG; no malignancy screen needed.

Stem 1: "45F with photosensitive annular plaques on chest/back after starting HCTZ 6 weeks ago; ANA+ speckled, anti-Ro+."

Stem 2: "52F with violaceous eyelid rash, knuckle papules, difficulty rising from chair × 3 months; CK 4200."

Stem 3: "28F SLE patient on HCQ planning pregnancy; anti-Ro/SSA+; what next?"

Stem 4: "60M with new amyopathic DM skin, rapidly worsening dyspnea over 2 weeks, HRCT with bilateral ground glass and consolidation, ferritin 3200."

Stem 5: "30F with discoid scarring plaques on scalp × 2 years, treated with topical steroids only; new hyperkeratotic nodule on lower lip."

Stem 6: "55F with DM on prednisone 60 mg × 8 weeks; weakness worsening but CK now 180."

Stem 7: "DM patient on HCQ × 6 years, no eye exam in 4 years."

Stem 8: "6yo with heliotrope, Gottron, calcinosis cutis."

CCS pearl: On a DM CCS case, place these orders in the first 15 minutes: CK, aldolase, AST/ALT, CMP, CBC, TSH, MSA panel, ANA, CXR, HRCT, PFTs, ECG, troponin, swallow eval, MRI thighs, dermatology + rheumatology + pulmonology consults, age-appropriate cancer screening + CT C/A/P + pelvic US + CA-125. Counsel sun protection, smoking cessation, vaccines, contraception.

One-Line Recap

Cutaneous lupus and dermatomyositis are photosensitive autoimmune skin diseases distinguished by pattern — malar/discoid/annular plaques sparing knuckles for lupus, heliotrope and Gottron papules over knuckles for dermatomyositis — that demand universal photoprotection, hydroxychloroquine, malignancy and ILD screening in adult DM, and pregnancy-specific planning around anti-Ro antibodies.

Diagnosis recap: Photodistribution + nasolabial sparing + ANA = think CLE; heliotrope + Gottron + proximal weakness + elevated CK = DM. Confirm with biopsy, ANA/ENA, MSA panel (TIF1-γ, MDA5, Jo-1, Mi-2), HRCT + PFTs in DM, and full age-appropriate cancer screen + CT C/A/P + pelvic US/CA-125 in adult DM annually × 3 years.

Treatment recap: Universal photoprotection, smoking cessation, vaccines before immunosuppression; HCQ for nearly all CLE (annual eye screening after 5 years); prednisone 1 mg/kg + methotrexate/MMF/AZA early in DM; IVIG, rituximab, JAK inhibitors for refractory disease; aggressive triple therapy for MDA5 rapidly progressive ILD; PJP prophylaxis when prednisone ≥20 mg + second immunosuppressant.

Special populations recap: Anti-Ro+ pregnancy → continue HCQ, fetal echo weekly 16–26 weeks for congenital heart block; juvenile DM has calcinosis and vasculopathy but no malignancy risk; mycophenolate/methotrexate/cyclophosphamide are teratogens requiring contraception and 3-month preconception washout.

Safety recap: Steroid myopathy mimics flare but has normal CK; DLE plaques can transform into SCC; anti-MDA5 + ferritin >1500 = high-mortality ILD requiring immediate aggressive immunosuppression; nasolabial sparing differentiates lupus malar from rosacea and seborrheic dermatitis; Gottron papules sit on knuckles whereas lupus hand rash spares them — the single highest-yield distinguishing fact for Step 3.

Board pearl: Master the antibody-phenotype map (Ro/SCLE/neonatal lupus; TIF1-γ/cancer; MDA5/RP-ILD; Mi-2/classic DM; Jo-1/antisynthetase) and you will correctly answer the majority of Step 3 stems on cutaneous lupus and dermatomyositis.