Pediatrics (System-Integrated)

Pediatric viral exanthems: measles, varicella, fifth disease, roseola

Clinical Overview and When to Suspect Pediatric Viral Exanthems

— Measles (rubeola): paramyxovirus, 1st disease; resurging in undervaccinated US clusters

— Varicella (chickenpox): VZV, herpesvirus family; now uncommon due to 2-dose vaccine but breakthrough cases occur

— Erythema infectiosum (fifth disease): parvovirus B19; school-age "slapped cheek"

— Roseola infantum (sixth disease, exanthem subitum): HHV-6 (occasionally HHV-7); infants 6–24 months

— Prodrome of fever, malaise, URI symptoms followed by rash

— Sick contacts, daycare exposure, recent travel, or incomplete immunization

— Mucosal involvement (Koplik spots in measles, enanthem in varicella)

— Self-limited course in an otherwise well-appearing child

Viral exanthems are generalized cutaneous eruptions caused by systemic viral infection, often with characteristic patterns that allow clinical diagnosis without testing

Four classic "numbered" exanthems still tested heavily on Step 3:

When to suspect a viral exanthem rather than bacterial or drug etiology:

Step 3 framing: most questions hinge on (1) identifying the virus from rash morphology and timing, (2) public health/exposure management (post-exposure prophylaxis, school exclusion, reporting), and (3) recognizing the at-risk contact (pregnant woman exposed to parvovirus, immunocompromised child exposed to varicella, infant <6 mo exposed to measles)

Ambulatory pediatrics is the default setting — anticipate counseling, return precautions, and contact tracing

Board pearl: The mnemonic order is Measles (1st), scarlet fever (2nd), Rubella (3rd), Dukes (4th, defunct), erythema infectiosum (5th), roseola (6th). Step 3 favors measles, varicella, fifth, and roseola because each carries a distinct management decision (PEP, antivirals, pregnancy counseling, reassurance respectively)

Presentation Patterns and Key History

— Immunization status (MMR, varicella doses)

— Sick contacts, daycare/school outbreaks, recent international travel

— Pregnant household contacts (parvovirus, rubella, varicella implications)

— Immunocompromised contacts

— Prior episode (varicella and measles confer lifelong immunity; roseola can rarely recur with HHV-7)

Measles: 8–12 day incubation, then 3 C's prodrome—cough, coryza, conjunctivitis—plus high fever (often 104°F) for 2–4 days; Koplik spots (blue-white papules on buccal mucosa opposite molars) appear 1–2 days before rash; morbilliform rash starts on face/behind ears and spreads cephalocaudally, becoming confluent, lasts ~5 days, may desquamate

Varicella: 10–21 day incubation; mild prodrome (low fever, malaise) then pruritic rash in successive crops—macules → papules → vesicles ("dewdrop on rose petal") → pustules → crusts; lesions in different stages simultaneously; begins on trunk/scalp, spreads centrifugally; mucosal lesions common

Fifth disease: low-grade fever and mild URI for several days, then "slapped cheek" facial erythema with circumoral pallor; 1–4 days later lacy reticular rash on extensor extremities and trunk; can recur with heat, sun, exercise for weeks; child is no longer contagious once rash appears

Roseola: abrupt high fever (often 39–40°C) for 3–5 days in a well-appearing infant 6–24 months; fever breaks and then a rose-pink macular/maculopapular rash appears on the trunk, spreading to neck and extremities, lasting hours to 2 days; Nagayama spots (uvulopalatoglossal papules) may be seen

Key history questions:

Key distinction: In roseola, the rash appears as fever resolves; in measles, fever peaks with the rash. This single timing rule resolves most Step 3 infant-fever-then-rash stems

Physical Exam Findings

— Koplik spots are pathognomonic; check buccal mucosa before rash onset

— Generalized lymphadenopathy, nonpurulent conjunctivitis with photophobia

— Rash: erythematous macules/papules, blanching, confluent on face, spreading downward; palms/soles spared

— Toxic-appearing child with high fever

— Polymorphic rash—macules, papules, vesicles, and crusts coexisting is the hallmark

— Vesicles on erythematous base ("dewdrop on rose petal")

— Scalp, oral mucosa, conjunctiva can be involved

— Check for secondary bacterial superinfection (Staph/GAS): warm, tender, fluctuant, surrounding cellulitis, or unexpected fever recurrence

— Bright erythematous cheeks with circumoral pallor

— Lacy/reticular rash on arms, legs, trunk—often more prominent in warm bath

— Arthralgia/arthritis in older children and adults (symmetric small joints); rare in young children

— Well-appearing

— Well-appearing infant once afebrile

— Blanching pink macules/papules, starts on trunk then spreads to neck/proximal extremities, spares face

— Mild cervical/occipital/postauricular lymphadenopathy

— Bulging fontanelle may be present during febrile phase (benign HHV-6 finding)

— Hydration status, capillary refill, mental status

— Respiratory exam—measles pneumonitis, varicella pneumonia (more in adolescents/adults/immunocompromised)

— Neurologic exam—measles encephalitis, varicella cerebellar ataxia

Measles:

Varicella:

Fifth disease:

Roseola:

Hemodynamic/severity assessment (especially measles, varicella):

Board pearl: A febrile child with rash on palms and soles is not one of these four exanthems—think RMSF, secondary syphilis, hand-foot-and-mouth (coxsackie), or Kawasaki

Diagnostic Workup — Initial Evaluation

— Report immediately to public health on suspicion—don't wait for confirmation

— Measles IgM and IgG serology (IgM positive 3 days–1 month after rash onset)

— RT-PCR from nasopharyngeal/throat swab, urine, or blood (most sensitive, especially early)

— CBC: often leukopenia with lymphopenia

— CXR if respiratory symptoms—look for pneumonitis

— Usually clinical; if confirmation needed (atypical, immunocompromised, or for infection control):

— PCR of vesicular fluid is gold standard (most sensitive/specific)

— Direct fluorescent antibody (DFA) of scraped vesicle base

— Tzanck smear shows multinucleated giant cells but does not differentiate HSV from VZV

— Serology (IgG) is used for immunity screening (e.g., healthcare workers, pre-pregnancy), not acute dx

— Clinical in healthy children

— Parvovirus B19 IgM and IgG in: pregnant women, immunocompromised, sickle cell/hereditary spherocytosis with aplastic crisis, suspected hydrops fetalis

— PCR for B19 DNA in immunocompromised (may not mount antibody)

— CBC with reticulocyte count if hemolytic anemia or aplastic crisis suspected—low retic count is the red flag

— Clinical diagnosis—no testing routinely indicated

— HHV-6 PCR available but rarely needed

General principle: most viral exanthems are clinical diagnoses; lab testing is reserved for public health reporting, atypical presentations, immunocompromised hosts, or pregnant contacts

Measles:

Varicella:

Fifth disease:

Roseola:

Step 3 management: When a pregnant woman is exposed to a child with fifth disease, send parvovirus B19 IgM and IgG within 7–10 days; if susceptible and infected, refer to MFM for serial fetal ultrasounds every 1–2 weeks for up to 12 weeks watching for hydrops fetalis from fetal anemia

Diagnostic Workup — Confirmatory and Outbreak Studies

— Paired acute and convalescent IgG (4-fold rise confirms) — rarely needed if PCR positive

— Genotyping of viral isolates by state lab during outbreaks to track transmission and distinguish wild-type from vaccine strain

— All suspected cases require respiratory (airborne) isolation during workup—negative-pressure room if hospitalized

— PCR distinguishes wild-type VZV from vaccine strain (Oka)

— In suspected varicella pneumonia: CXR shows diffuse nodular/interstitial infiltrates; consider CT

— LP if encephalitis or cerebellar ataxia suspected—VZV PCR on CSF

— In aplastic crisis (sickle cell, thalassemia, HS): CBC with low Hb, reticulocytopenia; B19 PCR confirms

— Hydrops fetalis workup: fetal MCA Doppler peak systolic velocity (>1.5 MoM suggests anemia), amniotic fluid PCR; intrauterine transfusion may be needed

— Chronic B19 in HIV/immunocompromised: persistent anemia, requires IVIG

— Rarely required; HHV-6 PCR if encephalitis (rare complication, especially in transplant patients) or atypical course

— PCR panels (multiplex respiratory + dermatologic viral panels) increasingly available

— Skin biopsy rarely needed except for atypical immunocompromised presentations

— Measles, rubella, and varicella outbreaks require state lab confirmation; private labs often forward specimens

— Document date of rash onset, vaccination history, exposure source, and contact list — these are reportable data elements

Measles confirmatory pathway:

Varicella confirmatory:

Parvovirus B19 advanced:

Roseola advanced:

Differentiating overlapping rashes—when in doubt:

Public health lab coordination:

CCS pearl: For a hospitalized child with suspected measles, order in this sequence on the CCS interface: place in airborne isolation, measles PCR (NP swab) + IgM, CBC, CXR if respiratory symptoms, then notify public health—advance the clock only after isolation is in place

Risk Stratification and First-Line Management Logic

— Healthy child: supportive care (hydration, antipyretics) + vitamin A for all hospitalized children and any child with measles—reduces morbidity/mortality

— Vitamin A dosing: 200,000 IU PO once daily × 2 days (50,000 IU if <6 mo; 100,000 IU if 6–11 mo)

— High risk for severe disease: <5 years, immunocompromised, pregnant, malnourished—hospitalize and isolate

— Healthy child <12 years: supportive only—calamine, antihistamines for itch, acetaminophen (avoid aspirin → Reye syndrome; avoid ibuprofen due to association with severe GAS skin infection)

— Acyclovir indicated for: >12 years, chronic skin/pulmonary disease, chronic salicylate therapy, immunocompromised, secondary household cases (often more severe), pregnant women

— Start acyclovir within 24 hours of rash onset for benefit

— Healthy child: reassurance—rash appears after contagious period; no isolation needed once rash present

— Pregnant contact: serology + MFM referral as above

— Aplastic crisis: hospitalize, transfuse PRBCs, droplet isolation (still viremic)

— Immunocompromised with chronic anemia: IVIG

— Supportive care only—antipyretics, fluids

— Reassure family that the rash is the resolution phase

— Simple febrile seizures may occur during fever spike (HHV-6 a leading cause)

— Toxic appearance, respiratory distress, altered mental status, dehydration → ED/admit

— Immunocompromised host with any exanthem → low threshold for admission and antiviral

— Pregnant exposure → serology + OB referral

Measles:

Varicella:

Fifth disease:

Roseola:

Triage decision tree:

Step 3 management: A 4-year-old unvaccinated child with measles, otherwise well, gets oral vitamin A × 2 days, supportive care, home isolation through day 4 after rash onset, and public health report—admission is not automatic

Pharmacotherapy — First-Line Regimens and Prophylaxis

— Vitamin A: as above; reduces ocular complications and mortality

— Post-exposure prophylaxis (PEP) for susceptible contacts:

— MMR within 72 hours of exposure (preferred if ≥6 months old and no contraindication)

— IG (immunoglobulin) within 6 days: IM IG (0.5 mL/kg, max 15 mL) for infants <6 mo, pregnant women, immunocompromised; IVIG (400 mg/kg) for severely immunocompromised

— No specific antiviral; ribavirin sometimes used in severe cases (not standard)

— Acyclovir 20 mg/kg/dose (max 800 mg) PO 4× daily × 5 days for indicated patients

— IV acyclovir 10 mg/kg q8h for severe disease, immunocompromised, varicella pneumonia, encephalitis

— PEP for susceptible contacts:

— Varicella vaccine within 3–5 days of exposure if ≥12 months and no contraindication

— VariZIG within 10 days for: immunocompromised, pregnant women, neonates whose mother developed varicella 5 days before to 2 days after delivery, hospitalized preterm infants

— Valacyclovir is an alternative in adolescents who can swallow tablets

— No antiviral; IVIG for chronic B19 in immunocompromised

— Pregnant exposure: no prophylaxis available—surveillance only

— None; antipyretics only

Measles:

Varicella:

Fifth disease:

Roseola:

Antipyretic note: acetaminophen 15 mg/kg q4–6h preferred; avoid aspirin in any viral illness in children (Reye syndrome risk, especially varicella and influenza)

Board pearl: MMR is contraindicated in pregnancy and severe immunocompromise—give IG instead for measles PEP in these groups. Same principle: varicella vaccine is live and contraindicated in pregnancy/immunocompromise; use VariZIG

Expanded Pharmacology and Vaccination Strategy

— Live attenuated; routine schedule: dose 1 at 12–15 months, dose 2 at 4–6 years

— Accelerated schedule for outbreak/travel: 1st dose as early as 6 months (doesn't count toward routine series; revaccinate at 12–15 mo and 4–6 yr)

— Contraindications: pregnancy, severe immunocompromise (CD4 <15% in HIV), anaphylaxis to neomycin/gelatin

— Mild illness or low-dose steroids are not contraindications

— Live attenuated; dose 1 at 12–15 months, dose 2 at 4–6 years

— Catch-up: 2 doses ≥3 months apart if <13 yr; ≥4 weeks apart if ≥13 yr

— MMRV combination available 12 mo–12 yr; slightly increased febrile seizure risk with 1st dose at 12–23 mo—give MMR and varicella separately for dose 1 in that age range (ACIP preference)

— Breakthrough varicella: milder, <50 lesions, often atypical—still infectious

— Nucleoside analog requires viral thymidine kinase for activation—selective for infected cells

— Renal elimination—adjust dose in renal impairment and ensure hydration (crystal nephropathy risk with IV)

— Resistance rare except in chronic immunocompromised use

— Purified human IgG; provides passive immunity for ~3 weeks

— Give ASAP, ideally within 96 hours, up to 10 days post-exposure

— Used in chronic B19 infection in HIV/immunocompromised with persistent anemia

— Typical: 400 mg/kg/day × 5–10 days

MMR vaccine:

Varicella vaccine:

Acyclovir pharmacology:

VariZIG:

IVIG for parvovirus:

Step 3 management: For an unvaccinated 9-month-old exposed to measles in a clinic waiting room, give MMR within 72 hours; if presenting at day 5, give IG instead. Either way, also report to public health and arrange home isolation through day 21

Special Populations — Immunocompromised and Comorbid Hosts

— Measles: high risk of giant cell pneumonia and measles inclusion body encephalitis; rash may be absent or atypical; admit, isolate, IVIG/IG PEP; avoid live MMR in severe immunosuppression

— Varicella: high risk of disseminated disease, visceral involvement (hepatitis, pneumonia, encephalitis), DIC; IV acyclovir mandatory; VariZIG for PEP; avoid live varicella vaccine in severe immunosuppression (CD4 <15% in HIV)

— Parvovirus B19: chronic anemia from persistent viremia; treat with IVIG

— HHV-6 (roseola): reactivation in transplant patients can cause encephalitis, pneumonitis, bone marrow suppression; consider foscarnet or ganciclovir

— Parvovirus B19 causes transient aplastic crisis—abrupt drop in Hb with reticulocytopenia

— Hospitalize, transfuse, droplet isolation (still viremic, unlike well children)

— Counsel families to seek care for pallor/fatigue during outbreaks

— Acyclovir is renally dosed—reduce dose with reduced CrCl; encourage hydration to prevent crystal nephropathy

— Hepatic dosing rarely required for these agents

— MMR and varicella vaccines acceptable if CD4 ≥15% and not severely symptomatic

— Two MMR doses 4 weeks apart for HIV+ kids without severe immunosuppression

Immunocompromised children (oncology, HIV, transplant, primary immunodeficiency, high-dose steroids):

Sickle cell disease and hereditary hemolytic anemias:

Renal/hepatic impairment:

HIV-positive children:

Asplenia, complement deficiency: not directly higher risk for these viral exanthems but watch for bacterial superinfection in varicella

Board pearl: A child with leukemia on chemotherapy exposed to varicella should receive VariZIG within 10 days, not the vaccine. If they develop disease, IV acyclovir and admission—this is one of the few absolute admissions for a "common" childhood rash

Special Populations — Pregnancy and Neonates

— Increased maternal morbidity (pneumonia), preterm labor, fetal loss; no congenital measles syndrome

— Susceptible pregnant exposure: IG (IVIG 400 mg/kg) within 6 days; MMR contraindicated in pregnancy (give postpartum)

— Maternal varicella pneumonia (10–20% of adult cases) carries significant mortality—hospitalize and IV acyclovir

— Congenital varicella syndrome if infection at <20 weeks: limb hypoplasia, cicatricial skin lesions, chorioretinitis, microcephaly, cataracts

— Neonatal varicella: maternal rash 5 days before to 2 days after delivery → severe neonatal disease (mortality up to 30%); give neonate VariZIG at birth and IV acyclovir if disease develops

— Susceptible pregnant exposure: VariZIG within 10 days; varicella vaccine contraindicated in pregnancy

— Greatest fetal risk at <20 weeks: hydrops fetalis from fetal anemia (B19 infects erythroid precursors) and miscarriage

— Overall fetal loss risk ~5–10% if maternal infection in first half of pregnancy

— Management: maternal IgM/IgG, MFM referral, serial fetal ultrasounds + MCA Doppler q1–2 weeks for 8–12 weeks; intrauterine transfusion for severe hydrops

— No long-term developmental sequelae in surviving infants—a frequent Step 3 distractor vs. rubella/CMV

— Any febrile rash in a neonate warrants full sepsis workup—don't anchor on viral exanthem

— Neonatal HSV is the critical mimic of varicella-like vesicles; treat empirically with IV acyclovir while testing

Measles in pregnancy:

Varicella in pregnancy:

Parvovirus B19 in pregnancy:

Roseola (HHV-6) in pregnancy: no significant teratogenic risk

Neonates (<28 days):

Step 3 management: Pregnant woman at 16 weeks with documented parvovirus B19 IgM → refer to MFM, start serial fetal ultrasounds with MCA Doppler every 1–2 weeks for up to 12 weeks; intrauterine transfusion if hydrops develops

Complications and Adverse Outcomes

— Otitis media (most common)

— Pneumonia (leading cause of measles death)—primary viral or secondary bacterial (S. pneumoniae, S. aureus)

— Acute postinfectious encephalitis (1 in 1000): days–weeks after rash

— Subacute sclerosing panencephalitis (SSPE): 7–10 years later, progressive neurodegeneration, fatal; higher risk if infected <2 years old

— Diarrhea, keratitis (worse with vitamin A deficiency)

— Immune amnesia—measles wipes immunologic memory for months to years

— Secondary bacterial skin infection (Group A Strep, S. aureus including MRSA)—most common; necrotizing fasciitis is the feared extreme

— Cerebellar ataxia (post-infectious, benign, self-limited)—classic week-after-rash gait disturbance

— Encephalitis (rare, more serious)

— Pneumonia (rare in healthy children; common in adults/immunocompromised)

— Reye syndrome if aspirin used

— Later in life: zoster (shingles) from reactivation

— Aplastic crisis in hemolytic anemias

— Hydrops fetalis in pregnancy

— Arthritis/arthralgia (symmetric small joints, adults > children, self-limited but can last weeks)

— Rare: myocarditis, glomerulonephritis, chronic anemia in immunocompromised

— Febrile seizures (leading viral cause)

— Rare: encephalitis, hepatitis in immunocompromised/transplant

Measles complications (occur in ~30% of cases):

Varicella complications:

Fifth disease complications:

Roseola complications:

Key distinction: Cerebellar ataxia post-varicella is benign and self-limited; encephalitis post-varicella or post-measles is dangerous and requires admission, LP, neuroimaging, and antivirals. Differentiate by mental status and focal findings, not gait alone

When to Escalate — Admission, ICU, and Consults

— Measles in <12 months, immunocompromised, or with pneumonia/encephalitis

— Varicella with secondary bacterial infection requiring IV antibiotics, pneumonia, encephalitis, immunocompromise, or neonatal disease

— Parvovirus aplastic crisis (transfusion + observation)

— Any exanthem with dehydration, toxic appearance, or altered mental status

— Suspicion of necrotizing fasciitis—surgical emergency

— Respiratory failure (measles or varicella pneumonia)

— Encephalitis with decreased GCS, status epilepticus

— Septic shock from bacterial superinfection

— Neonatal varicella with multisystem involvement

— Infectious disease: complicated/atypical cases, immunocompromised, drug resistance concerns

— Public health (mandatory): measles, suspected rubella, outbreak clusters

— Maternal-fetal medicine: pregnant women with B19, varicella, or measles exposure

— Hematology: aplastic crisis, chronic B19 anemia

— Dermatology: atypical/diagnostic uncertainty

— Neurology: encephalitis, prolonged ataxia, suspected SSPE

— Ophthalmology: measles keratitis, varicella ocular involvement

— Measles: airborne (negative-pressure room) + standard; isolate through 4 days after rash onset (longer in immunocompromised)

— Varicella: airborne + contact; until all lesions crusted

— Parvovirus B19: droplet only if aplastic crisis or chronic infection (no longer infectious once rash appears in healthy child)

— Roseola: standard precautions

Admit for inpatient management:

ICU criteria:

Consults:

Isolation precautions on admission:

CCS pearl: For a febrile, toxic-appearing child with morbilliform rash and Koplik spots, your first three CCS orders are: place in airborne isolation, IV fluids, vitamin A—then send PCR/serology, CXR, and notify public health. Don't advance the clock before isolation

Key Differentials — Same Category (Other Viral Exanthems)

— Milder than measles; pink macular rash starting on face, spreading caudally, resolving in 3 days

— Forchheimer spots (petechiae on soft palate)

— Posterior auricular, suboccipital, posterior cervical lymphadenopathy is the giveaway

— Critical for pregnancy: congenital rubella syndrome (cataracts, sensorineural deafness, PDA/pulmonary artery stenosis, "blueberry muffin" rash)

— Vesicles on palms, soles, and oral ulcers; fever

— Coxsackie A6 causes more extensive, eczema-like rash

— Palms/soles involvement distinguishes from varicella (which spares palms/soles)

— Posterior oropharyngeal vesicles/ulcers without rash; high fever

— Rash often after amoxicillin given for "strep"; pharyngitis, posterior cervical adenopathy, splenomegaly

— Herald patch, then "Christmas tree" truncal distribution; older children/adolescents

— Symmetric papules on cheeks, extensor extremities, buttocks; associated with HBV, EBV, others

— Asymmetric rash beginning in axilla, presumed viral

Rubella (German measles, 3-day measles):

Hand-foot-and-mouth disease (coxsackievirus A16, enterovirus 71):

Herpangina (coxsackie A):

Infectious mononucleosis (EBV):

Pityriasis rosea (possibly HHV-6/7):

Gianotti-Crosti (papular acrodermatitis of childhood):

Unilateral laterothoracic exanthem:

Key distinction: Varicella = polymorphic vesicles in different stages, includes scalp/mucosa, spares palms/soles. HFMD = vesicles concentrated on palms, soles, mouth, in similar stages. Fifth disease = facial slapped cheek + lacy reticular rash, no vesicles. Roseola = fever-then-rash, no vesicles, well-appearing infant. Measles = morbilliform, Koplik spots, toxic-appearing, cephalocaudal spread

Key Differentials — Non-Viral Causes of Pediatric Rash + Fever

— Sandpaper rash, strawberry tongue, circumoral pallor, Pastia lines in flexural creases, desquamation; preceding pharyngitis

— Treat with penicillin/amoxicillin × 10 days to prevent rheumatic fever

— Fever ≥5 days plus 4 of: bilateral nonexudative conjunctivitis, mucositis (strawberry tongue, cracked lips), polymorphic rash, extremity changes (edema/desquamation), cervical lymphadenopathy (≥1.5 cm, usually unilateral)

— Coronary aneurysm risk → IVIG + aspirin within 10 days

— Fever, headache, then rash starting on wrists/ankles spreading centrally and to palms/soles, petechial

— Treat doxycycline empirically in any age—including young children—when suspected

— Rapidly progressive petechial/purpuric rash, fever, shock

— Emergent empiric ceftriaxone, supportive care, droplet isolation, contact prophylaxis

— Morbilliform drug rash (amoxicillin, sulfa)—mimics measles but lacks Koplik spots, conjunctivitis, cough

— SJS/TEN: mucosal involvement, skin sloughing—emergency

Scarlet fever (Group A Strep):

Kawasaki disease:

Rocky Mountain spotted fever (Rickettsia rickettsii):

Meningococcemia:

Drug eruptions:

DRESS: fever, rash, eosinophilia, hepatitis, lymphadenopathy 2–8 weeks after drug initiation

Erythema multiforme: target lesions, often post-HSV or mycoplasma

Henoch-Schönlein purpura (IgA vasculitis): palpable purpura on buttocks/lower extremities, arthritis, abdominal pain, hematuria

Staphylococcal scalded skin syndrome: tender erythema, positive Nikolsky, periorificial accentuation

Board pearl: Petechiae below the nipple line in a febrile child = consider meningococcemia or RMSF until proven otherwise; petechiae only above the nipple line in a vigorously coughing/vomiting child are usually benign mechanical purpura

Secondary Prevention, Public Health, and Long-Term Plan

— MMR: dose 1 at 12–15 mo, dose 2 at 4–6 yr; catch up adolescents/adults if susceptible

— Varicella: dose 1 at 12–15 mo, dose 2 at 4–6 yr; 2 doses ≥4 wk apart for adolescents/adults

— Document immunity for healthcare workers, college students, international travelers

— No vaccine for parvovirus B19 or HHV-6

— Measles, rubella, varicella are reportable in all US states (timeline varies; measles is immediate)

— Identify all contacts during infectious period (measles: 4 days before to 4 days after rash; varicella: 1–2 days before rash until lesions crusted)

— Offer PEP to susceptible contacts (MMR/IG, varicella vaccine/VariZIG)

— Exclude from school/daycare:

— Measles: through day 4 after rash onset (longer if immunocompromised)

— Varicella: until all lesions crusted (~5–7 days)

— Fifth disease: no exclusion—not contagious once rash appears

— Roseola: no specific exclusion; until afebrile

— Confirm vaccination plan for siblings/household

— Counsel on secondary attack risk (varicella household secondary attack ~90% in susceptibles)

— Schedule follow-up for resolution and any complication screening (e.g., audiology after measles, cardiac follow-up post-Kawasaki if that was the differential)

— Pre-conception screening for rubella/varicella immunity; vaccinate if susceptible, then wait 4 weeks before conception

Vaccination as primary prevention:

Outbreak/public health response:

Discharge planning after hospitalization:

Pregnancy planning:

Step 3 management: A measles case in your clinic triggers: (1) immediate phone report to local health dept, (2) line list of all patients/staff in waiting room during exposure window, (3) review of immunization records, (4) offer of MMR within 72 hr or IG within 6 days to susceptibles, (5) home isolation through day 4 after rash

Follow-Up, Monitoring, and Counseling

— Phone or visit follow-up in 24–48 hours for any home-managed case to confirm clinical course

— Monitor for complications: persistent fever (suggests bacterial superinfection or pneumonia), neurologic changes (encephalitis), ear pain (OM)

— Audiology screening after recovery if hearing concerns

— Long-term: counsel on SSPE risk (rare); ensure siblings vaccinated

— Re-administer MMR after recovery if patient was previously unvaccinated and age-eligible (natural infection confers immunity but documentation matters for school)

— Daily symptom check by parents; return for unexpected fever recurrence, expanding redness/pain (superinfection), focal neurologic symptoms, respiratory distress

— Skin care: trim fingernails, oatmeal baths, antihistamines for pruritus, avoid aspirin/ibuprofen

— Counsel about future zoster risk (lower with vaccine-derived immunity than wild-type)

— Reassure rash can recur for weeks with heat/sun/exercise—not reinfection

— Pregnant household members: serology + MFM if susceptible

— Sickle cell/HS patients: monitor CBC, transfuse if aplastic crisis

— Reassure on rash significance (resolution phase)

— Febrile seizure counseling: most are simple, do not increase epilepsy risk; cool, position safely, time seizure, ED if >5 minutes or focal

— Routine well-child care; ensure MMR/varicella on schedule

— Hydration, antipyretic dosing (acetaminophen), no aspirin

— Return precautions: lethargy, dehydration, respiratory distress, neurologic symptoms, expanding skin infection

— School/daycare return rules per above

Measles:

Varicella:

Fifth disease:

Roseola:

Anticipatory counseling for all exanthems:

Board pearl: A child with fifth disease can return to school immediately because contagiousness ended before rash appeared. A child with varicella stays home until all lesions crusted, typically 5–7 days. Memorize these two opposing rules — high-yield distractor pair

Ethical, Legal, and Patient Safety Considerations

— Measles is immediately reportable (within 24 hours, sometimes by phone) to local/state health departments in every state

— Varicella and rubella also reportable; timelines vary

— Failure to report is both a public health failure and a legal liability

— Respect parental autonomy but document conversations using a structured refusal form (AAP refusal-to-vaccinate form)

— Continue offering vaccination at each visit; do not dismiss families from the practice unilaterally without ethical/legal review (AAP allows but with cautions)

— Public health emergency exceptions: during outbreaks, schools may exclude unvaccinated students even with religious/philosophical exemptions—this is constitutional (Jacobson v. Massachusetts)

— Provide Vaccine Information Statements (VIS) before each dose (legal requirement under National Childhood Vaccine Injury Act)

— Counsel about contraindications (pregnancy, immunocompromise) and mild side effects (fever, rash, febrile seizure risk with MMRV)

— Hospital-to-home handoff: ensure household contacts identified, PEP arranged, school exclusion communicated

— Closed-loop communication with public health and PCP

— Document immunization status clearly in discharge summary

— Adolescent patients (varicella PEP, pregnancy testing for rubella vaccination eligibility) — observe state minor consent laws

— Susceptible HCWs exposed to measles/varicella must be furloughed during incubation window

— Pre-employment immunity documentation is standard of care

— Suspected measles or varicella → mask the patient, move directly to a private room (ideally negative-pressure), notify staff to avoid the room for 2 hours after patient leaves (airborne pathogens lingering)

Mandatory reporting:

Vaccine refusal:

Informed consent for live vaccines:

Transition-of-care safety:

Confidentiality:

Healthcare worker exposure:

Patient safety in clinic flow:

Step 3 management: Your clinic identifies a confirmed measles case retroactively. Required next steps: notify public health within 24 hours, generate a contact list of everyone in the waiting room during the patient's visit (and 2 hours after departure), offer PEP, and review staff immunity—failure here is both a patient safety event and a reportable lapse

High-Yield Associations and Rapid-Fire Facts

Koplik spots → measles (precede rash by 1–2 days; pathognomonic)

Three C's (cough, coryza, conjunctivitis) → measles prodrome

Cephalocaudal rash spread → measles and rubella

Lesions in different stages → varicella

Dewdrop on rose petal → varicella vesicle

Slapped cheek + lacy rash → erythema infectiosum (parvovirus B19)

Aplastic crisis in sickle cell → parvovirus B19

Hydrops fetalis from maternal infection in 1st half of pregnancy → parvovirus B19

High fever × 3–5 days, then rash as fever breaks, well-appearing infant → roseola (HHV-6)

Febrile seizure association → HHV-6 (roseola)

Nagayama spots (uvulopalatoglossal papules) → roseola

Forchheimer spots (soft palate petechiae) → rubella

Postauricular/suboccipital lymphadenopathy → rubella

SSPE → late measles complication, 7–10 years later

Reye syndrome → aspirin + varicella or influenza

Cerebellar ataxia 1 week after vesicular rash → post-varicella, benign

Congenital varicella syndrome → limb hypoplasia, cicatricial skin lesions, chorioretinitis

Neonatal varicella highest mortality window → maternal rash 5 days before to 2 days after delivery

Vitamin A treatment → measles (reduces mortality, especially in undernourished)

VariZIG → varicella PEP in pregnant, immunocompromised, neonate, preterm

MMR PEP within 72 hours of measles exposure; IG within 6 days for those who can't get vaccine

Vaccine ages: MMR + varicella at 12–15 mo, then 4–6 yr

Live vaccines (MMR, varicella) contraindicated in pregnancy and severe immunocompromise

Airborne isolation → measles and varicella

No isolation after rash appears → fifth disease

Most common measles cause of death → pneumonia

Most common measles complication overall → otitis media

Board pearl: If a Step 3 stem features a pregnant woman with a child who has a rash, the answer almost always hinges on identifying parvovirus B19 (hydrops risk) or varicella (congenital syndrome or neonatal disease); rubella appears less commonly given vaccination but remains a classic distractor

Board Question Stem Patterns

— Next step: airborne isolation + vitamin A + report to public health

— Wrong answers: oseltamivir, amoxicillin, IVIG

— Healthy child: supportive care

— If >12 yr, immunocompromised, secondary household case, or pregnant: oral or IV acyclovir

— Next step: maternal parvovirus B19 IgM/IgG; MFM referral with serial fetal ultrasounds + MCA Doppler

— Next step: reassurance and supportive care

— Wrong answers: blood cultures, ceftriaxone, MRI brain

— Management: PRBC transfusion + droplet isolation + B19 PCR

"Unvaccinated 4-year-old returns from international travel, high fever, cough, coryza, conjunctivitis, blue-white spots on buccal mucosa" → measles

"5-year-old with low-grade fever and pruritic rash with macules, papules, vesicles, and crusts simultaneously on trunk and scalp" → varicella

"7-year-old with bright red cheeks and lacy rash on arms; mother is 14 weeks pregnant" → fifth disease

"10-month-old with 4 days of high fever now defervesced; pink macular rash on trunk; well-appearing" → roseola

"Sickle cell patient with sudden pallor, fatigue, Hb 5, reticulocyte count near zero, recent rash exposure at school" → parvovirus B19 aplastic crisis

"9-month-old exposed to measles in clinic waiting room 2 days ago" → MMR within 72 hours

"6-month-old exposed to measles 5 days ago" → IG (too young/too late for vaccine alone)

"Newborn delivered to mother with chickenpox 3 days ago" → VariZIG; admit and monitor; IV acyclovir if disease develops

"Toddler develops febrile seizure during peak of fever, then rash appears 2 days later" → roseola; counsel on simple febrile seizure

"Adult or adolescent with chickenpox and dyspnea" → varicella pneumonia → admit, IV acyclovir

"Child 1 week post-varicella with wide-based gait, intention tremor, otherwise well" → post-varicella cerebellar ataxia → supportive, self-limited

Step 3 management: When the stem includes timing of exposure, immediately calculate the PEP window (3 days for measles vaccine, 6 days for IG; 5 days for varicella vaccine, 10 days for VariZIG). The correct answer almost always tracks that window

One-Line Recap

Pediatric viral exanthems—measles, varicella, fifth disease, and roseola—are largely clinical diagnoses where Step 3 success depends on matching rash morphology and timing to the right virus, then executing virus-specific public health, prophylaxis, and special-population management (pregnant or immunocompromised contacts especially).

— Measles = 3 C's + Koplik + cephalocaudal morbilliform rash + toxic child

— Varicella = pruritic vesicles in different stages, scalp + mucosa involved

— Fifth disease = slapped cheek + lacy reticular rash, well child

— Roseola = high fever × 3–5 days, then rash appears as fever breaks, well infant

— Measles: vitamin A, airborne isolation, public health report, MMR (≤72 hr) or IG (≤6 days) PEP

— Varicella: acyclovir if >12 yr/immunocompromised/pregnant/secondary case; VariZIG for high-risk PEP within 10 days

— Fifth disease: pregnant exposure → serology + MFM + serial fetal ultrasounds with MCA Doppler

— Roseola: reassurance + febrile seizure counseling

— Parvovirus B19 → aplastic crisis in sickle cell, hydrops in pregnancy

— Neonatal varicella from peripartum maternal infection (5 days before to 2 days after delivery) → VariZIG + IV acyclovir

— SSPE as a late measles complication

— Live vaccines (MMR, varicella) contraindicated in pregnancy and severe immunocompromise → use immunoglobulin products instead

Pattern recognition shortcuts:

Critical management triggers:

Don't miss:

School exclusion quick-recall: measles through day 4 after rash; varicella until lesions crusted; fifth disease no exclusion; roseola until afebrile

Board pearl: When the stem gives you a sick contact, pregnancy, or immunocompromised host, the test isn't really about the rash—it's about whom to protect and how, within what time window. Anchor on that and the answer falls out