Multisystem Processes & Disorders

Acute intermittent porphyria: recognition and management

Clinical Overview and When to Suspect Acute Intermittent Porphyria

— Severe, poorly-localized abdominal pain without peritoneal signs and with a normal abdominal exam/imaging

— Autonomic instability: tachycardia, hypertension, diaphoresis, nausea/vomiting, constipation

— Neuropsychiatric features: anxiety, agitation, confusion, seizures, or motor-predominant peripheral neuropathy

— Hyponatremia (SIADH-like) and red/port-wine urine on standing

Acute intermittent porphyria (AIP) is an autosomal dominant defect in hydroxymethylbilane synthase (HMBS), the third enzyme of heme biosynthesis, leading to accumulation of neurotoxic porphobilinogen (PBG) and δ-aminolevulinic acid (ALA) during attacks.

Most carriers are asymptomatic; only ~10% develop overt attacks. Penetrance is markedly higher in women aged 18–45, reflecting hormonal triggers.

Suspect AIP when a patient presents with the classic triad-plus:

Classic triggers (the "4 M's plus"): Medications (CYP450 inducers — phenobarbital, phenytoin, carbamazepine, rifampin, sulfonamides, progesterone), Menstruation (luteal phase), Malnutrition/fasting/low-carb dieting, alcohol, smoking, infection, and surgical stress.

Step 3 management: When a young woman has recurrent ED visits for unexplained abdominal pain, autonomic symptoms, and negative surgical workup (often after a negative exploratory laparotomy or cholecystectomy), order spot urine PBG before the attack resolves — this is the single most important diagnostic move.

Board pearl: AIP is one of four acute hepatic porphyrias (along with hereditary coproporphyria, variegate porphyria, and ALA-dehydratase deficiency). All four share the acute neurovisceral attack phenotype because ALA and PBG are the neurotoxic intermediates, not the downstream porphyrins.

Mortality from untreated attacks: respiratory failure from ascending paralysis, arrhythmia from autonomic storm, status epilepticus. Early recognition prevents these.

Presentation Patterns and Key History

— Abdominal pain (>90%): severe, colicky or constant, diffuse, often with vomiting and constipation/ileus; pain is out of proportion to a benign exam.

— Autonomic surge: sinus tachycardia (>100), labile hypertension, urinary retention, sweating.

— CNS/PNS: insomnia, restlessness, hallucinations, confusion progressing to generalized tonic-clonic seizures; motor neuropathy beginning proximally in arms (atypical — unlike GBS which is distal/ascending).

— Psychiatric: depression, anxiety, frank psychosis — patients are often misdiagnosed as somatization, conversion, or factitious disorder.

— Family history of "unexplained abdominal surgeries," psychiatric admissions, or neuropathy

— Recurrent attacks linked to menstrual cycle (premenstrual)

— Recent starvation, crash diet, bariatric postop, ketogenic diet — heme synthesis is upregulated when glucose is scarce

— New medication, especially anticonvulsants, antibiotics, OCP, or anesthetic exposure

— Dark/reddish urine noticed by patient (PBG polymerizes to porphobilin on standing/light exposure)

— Alcohol binge or smoking escalation

Prototypical attack evolves over 1–3 days and lasts 4–14 days if untreated:

Key historical clues to elicit:

Key distinction: Unlike lead poisoning (which also elevates ALA via ALA-dehydratase inhibition and mimics AIP), AIP patients have normal lead levels and elevated PBG (lead poisoning has normal-to-mildly-elevated PBG because the block is earlier).

Step 3 management: On the CCS, when a 28-year-old woman presents with her third ED visit in a year for abdominal pain after starting phenytoin or a new OCP — pause before ordering another CT. Order urine PBG, ALA, and porphyrins during the symptomatic period.

Board pearl: Hyponatremia in an AIP attack is multifactorial — SIADH from hypothalamic involvement, plus GI/renal sodium losses. Rapid correction risks central pontine myelinolysis in this already neurologically vulnerable patient.

Physical Exam Findings and Hemodynamic Assessment

— Sinus tachycardia (80–90% of attacks) — a key objective marker of attack severity

— Labile hypertension with surges; occasionally orthostatic hypotension from autonomic dysfunction

— Low-grade fever possible; high fever should prompt search for precipitating infection

— Respiratory rate may rise late (impending diaphragmatic weakness)

— Mental status: anxious, agitated, sometimes frankly psychotic or delirious

— Cranial nerves usually intact early; bulbar weakness is a late ominous sign

— Motor: proximal upper-extremity weakness is classic and counterintuitive; reflexes are typically preserved or hyperactive early, then lost

— Sensory loss is variable, often a "bathing-suit" distribution

— Watch for respiratory muscle weakness — check negative inspiratory force (NIF) and vital capacity (VC) serially

Vital signs dominate the exam:

Abdominal exam: strikingly benign relative to reported pain — soft, no rebound, no guarding, no peritoneal signs. Bowel sounds decreased (ileus). No organomegaly. No jaundice (distinguishes from acute hepatic crises of other etiologies).

Neurologic exam:

Skin: AIP patients have NO photosensitive skin lesions — this distinguishes AIP from variegate porphyria and hereditary coproporphyria, which can have both neurovisceral attacks AND cutaneous blistering.

Urine inspection at bedside: Freshly voided urine may be normal-colored; on standing in light it darkens to port-wine/burgundy as PBG oxidizes — a classic but insensitive sign.

Key distinction: AIP is non-cutaneous; porphyria cutanea tarda (PCT) is cutaneous-only without attacks. If a patient has both photosensitive blisters AND neurovisceral attacks, think variegate porphyria (common in South African Afrikaners).

CCS pearl: Document serial NIF/VC q4–6h during admission. Falling VC <15 mL/kg or NIF less negative than −20 cmH₂O mandates ICU transfer for likely intubation — respiratory failure is the leading cause of death in AIP.

Diagnostic Workup — Initial Labs, Imaging, ECG, Biomarkers

— PBG is markedly elevated (>5× upper limit, often 20–200×) during attacks in AIP, HCP, and VP.

— A normal PBG during active symptoms essentially rules out an acute porphyria attack — high negative predictive value.

— Send urine ALA and total urine porphyrins at the same time on the same sample to speed workup.

— Protect sample from light; refrigerate.

— CBC, CMP — look for hyponatremia (SIADH), hypomagnesemia, hypokalemia, mild transaminase elevation

— Lipase, LFTs, lactate — exclude pancreatitis, hepatitis, mesenteric ischemia

— Pregnancy test in reproductive-age women (pregnancy itself can trigger attacks; also affects management)

— Lead level to exclude plumbism

— TSH, urine/serum tox as appropriate

First-line single test: spot urine porphobilinogen (PBG), quantitative, collected during the acute attack.

Avoid the Watson-Schwartz screen (qualitative) — too insensitive and nonspecific; modern labs use quantitative immunoassay or ion-exchange chromatography.

Supportive labs to order concurrently:

ECG: sinus tachycardia is the rule; watch for QT prolongation (electrolyte-driven) and arrhythmias during autonomic storms.

Imaging: CT abdomen/pelvis is typically obtained but classically normal — order it once to exclude surgical abdomen; do not repeat on subsequent attacks if prior workup was negative.

Step 3 management: The exam loves the scenario of a young woman who has had three negative CT scans for recurrent abdominal pain — the next step is urine PBG, not another CT. This both spares radiation and clinches diagnosis.

Board pearl: Hyponatremia + abdominal pain + tachycardia + reddish urine in a young woman = AIP until proven otherwise. Send urine PBG before fluids dilute the sample and before symptoms resolve, because PBG normalizes between attacks.

Diagnostic Workup — Advanced and Confirmatory Studies

— Plasma fluorescence emission scan: peak at 626 nm suggests variegate porphyria; flat scan favors AIP.

— Fecal porphyrins: elevated coproporphyrin III in HCP; elevated proto- and copro-porphyrin in VP; normal or mildly elevated in AIP.

— Urinary uroporphyrin and coproporphyrin: elevated in all three but pattern differs.

— Identifies the family-specific pathogenic variant

— Enables cascade screening of first-degree relatives (asymptomatic carriers can then avoid triggers)

— Required for enrollment in givosiran therapy and for definitive diagnosis when biochemical results are ambiguous

— AIP: ↑ALA, ↑↑PBG, ↑uroporphyrin; normal fecal porphyrins

— HCP: ↑ALA, ↑PBG, ↑↑fecal coproporphyrin III

— VP: ↑ALA, ↑PBG, ↑fecal proto + copro porphyrin, plasma peak 626 nm

— Lead poisoning: ↑↑ALA, normal or mildly ↑ PBG, ↑zinc protoporphyrin, elevated lead

Once urine PBG is elevated, distinguish among the acute hepatic porphyrias to guide counseling and prognosis:

Erythrocyte HMBS (PBG-deaminase) activity: ~50% of normal in AIP carriers. Useful but 15% of AIP patients have normal erythrocyte HMBS (variant with tissue-specific expression), so a normal level does not exclude AIP.

Genetic testing — HMBS gene sequencing is the gold standard confirmatory test:

Between-attack testing pitfall: PBG, ALA, and porphyrins can normalize between attacks, especially in mild disease. If suspicion is high but spot PBG is normal during quiescence, refer to a porphyria center of excellence for provoked testing and genetic confirmation.

24-hour urine is more sensitive than spot but slower; spot urine indexed to creatinine is the practical compromise in the ED.

Key distinction:

Board pearl: A 30-year-old with elevated urine PBG plus photosensitive vesicles on sun-exposed skin = variegate porphyria, not AIP. The neurovisceral management is identical, but cutaneous counseling differs.

Step 3 management: After biochemical confirmation, refer the patient and first-degree relatives to genetics for HMBS sequencing — this is a board-favored secondary action.

Risk Stratification and First-Line Management Logic

— Mild attack: pain controllable with oral/IV analgesia, no neuropathy, no hyponatremia, no seizures, tolerating PO. Manage on a general medical floor with carbohydrate loading and trigger removal; hemin if no improvement in 24–36 h.

— Moderate-to-severe attack: uncontrolled pain, vomiting precluding PO, hyponatremia (Na <125), tachycardia >100, motor weakness, seizures, or psychiatric decompensation → admit, start IV hemin promptly.

— Critical attack: bulbar/respiratory weakness, autonomic instability requiring vasoactive support, status epilepticus, falling VC → ICU.

— Arrange admission and consult a porphyria specialist if available

— Block further harm: stop all unsafe drugs (check the American Porphyria Foundation drug database at the bedside)

— Carbohydrate load: IV D10 at 1.5–2 L/day (≥300 g glucose/day) only as a bridge for ≤24 h or in mild attacks; do not delay hemin for moderate-severe disease

— Deliver hemin (Panhematin) 3–4 mg/kg IV daily × 4 days — the definitive treatment

— Electrolytes, hydration, treat triggers (infection, fasting)

— Don't give metoclopramide for nausea (unsafe) — use ondansetron (safe)

— Don't give diazepam/phenytoin for seizures — use levetiracetam, gabapentin, or magnesium

— Don't give NS bolus if Na <130 without careful titration — risks osmotic demyelination after correction

Stratify each attack by severity to choose level of care and tempo of therapy:

Universal first steps for every attack (the "ABCDE" of AIP):

Step 3 management: The board-correct first medication in a moderate-to-severe attack is IV hemin, not glucose. Glucose alone is reserved for mild attacks or as a bridge while hemin is procured. Hemin should be started within 24 hours for best neurologic outcomes.

Avoid these reflexive moves:

Board pearl: Both glucose and hemin work by feedback inhibition of hepatic ALA synthase 1 (ALAS1), reducing production of the neurotoxic ALA and PBG. Hemin is far more potent.

CCS pearl: Place a central line early — hemin causes phlebitis in peripheral veins.

Pharmacotherapy — First-Line Drug Regimen

— Dose: 3–4 mg/kg IV once daily × 4 consecutive days

— Reconstitute in human albumin (not sterile water) to reduce phlebitis and improve stability

— Administer through a large-bore peripheral or central line over 30–60 min

— Onset of symptom relief: pain and autonomic features improve in 24–48 h; neuropathy and psych symptoms recover over weeks

— Adverse effects: phlebitis, transient anticoagulant effect (factor consumption), iron overload with repeat dosing, rare anaphylaxis

— 300–500 g/day (≈1.5–2 L of D10) for mild attacks or as bridge to hemin

— Monitor for hyponatremia worsening (free water load) — consider D10½NS if Na borderline

— Pain: morphine, fentanyl, hydromorphone, acetaminophen, gabapentin

— Nausea: ondansetron, prochlorperazine (low-dose, short course)

— Anxiety/agitation: lorazepam (short course)

— Hypertension/tachycardia: propranolol, labetalol, or atenolol

— Seizures: levetiracetam, gabapentin, magnesium sulfate, IV propofol for status (safe)

— Insomnia: chloral hydrate or low-dose benzodiazepine

— 2.5 mg/kg SC monthly for patients with ≥2 attacks/year

— Reduces attack rate ~70%; adverse effects: injection-site reactions, elevated LFTs, ↑creatinine, hyperhomocysteinemia

— Not for acute attacks — prophylactic only

Hemin (hematin / heme arginate; Panhematin in the US):

IV glucose (D10W):

Symptom-directed therapy (use only porphyria-safe drugs):

Unsafe drugs to remember (mnemonic "P-BARS"): Phenobarbital/Phenytoin/Pyrazinamide, Barbiturates, Alcohol/Anticonvulsants (most), Rifampin/Rifabutin, Sulfonamides, Spiromolactone, plus carbamazepine, valproate, ergots, ketoconazole, metoclopramide, progesterone, OCPs (estrogen-progestin).

Givosiran (siRNA against hepatic ALAS1):

Board pearl: Hemin works by negative feedback on ALAS1, the rate-limiting enzyme; this collapses ALA/PBG production within hours.

Step 3 management: Always cross-check every order with the porphyria-safe drug list before clicking "submit" on the CCS — this is a frequent test of safety culture.

Procedures and Advanced Pharmacology

— Indicated for patients with recurrent disabling attacks refractory to hemin and givosiran, or progressive neurologic disability

— Within 24–48 h post-transplant, ALA/PBG normalize and attacks cease

— Combined liver-kidney transplant if CKD has developed (porphyria-associated nephropathy)

— Preoperative: carbohydrate load the night before; avoid prolonged fasting

— Anesthesia: propofol is safe; avoid barbiturates (thiopental), etomidate, ketamine; volatile agents — sevoflurane and isoflurane are acceptable; avoid enflurane

— Muscle relaxants: succinylcholine, vecuronium, rocuronium are safe

— Postoperative: monitor PBG if attack symptoms emerge; have hemin available

Liver transplantation is the only curative therapy:

Givosiran (Givlaari): monthly SC injection; first FDA-approved RNAi for AIP (2019). Reduces hepatic ALAS1 mRNA by ~85%. Monitor LFTs at baseline, monthly × 6 months, then periodically; monitor eGFR; supplement B6, B12, folate to mitigate hyperhomocysteinemia.

Prophylactic hemin infusions: weekly or twice-weekly hemin can be used in patients with menstrual-cycle-triggered attacks as a bridge to givosiran or while awaiting transplant. Risk: iron overload, port thrombosis, tachyphylaxis.

GnRH agonists (leuprolide): for premenstrual attacks refractory to other measures — suppress ovulation and luteal progesterone surge. Add-back estrogen (transdermal) considered to protect bone.

Procedural pearls for the porphyric patient undergoing surgery:

Hemodialysis: does NOT remove PBG/ALA effectively and is not therapeutic; reserved for AKI/uremia.

Key distinction: Hemin = acute attack treatment. Givosiran = prevention of recurrent attacks. Transplant = cure. Glucose = bridge or mild attacks only.

CCS pearl: In CCS, after starting hemin and stabilizing the patient, "consult hepatology/genetics" and "counsel patient on trigger avoidance" earn credit. Don't forget to schedule outpatient follow-up in 1–2 weeks with a porphyria specialist.

Board pearl: Tin protoporphyrin and afamelanotide are investigational; not Step 3 answers in 2024.

Special Populations — Elderly and Renal/Hepatic Impairment

— First attack after age 50 is rare — when it occurs, scrutinize for new triggers: recently started medications (statins are safe; rifampin, sulfa, antifungals are not), bariatric-style weight loss, alcohol escalation, or new malignancy.

— Coexisting illness complicates diagnosis: mesenteric ischemia, diverticulitis, malignancy must be excluded; AIP rarely produces an acute abdomen with peritoneal signs, so a rigid abdomen pushes you toward surgical pathology.

— Autonomic surges (HTN, tachycardia) carry higher cardiovascular risk — monitor troponin, ECG, and use beta-blockers liberally.

— AIP-associated chronic kidney disease affects up to 50% of long-standing patients — mechanism: chronic ALA-mediated tubular toxicity, hypertension, and possibly direct nephrotoxicity.

— Annual eGFR and urine albumin/creatinine screening is standard.

— Givosiran can raise serum creatinine and worsen proteinuria — monitor closely; dose adjustment not required in mild-moderate CKD but use cautiously in eGFR <30.

— Hemin: no dose adjustment for renal failure.

— Avoid NSAIDs for pain in CKD-AIP patients (renal risk), and avoid nephrotoxic antibiotics like aminoglycosides when possible.

— Chronic AIP increases hepatocellular carcinoma (HCC) risk ~35× — screen with liver US + AFP every 6–12 months starting at age 50 in all symptomatic AIP patients (some experts say at diagnosis).

— Hemin is hepatically processed; in active hepatitis or cirrhosis, monitor LFTs more frequently but still administer for acute attacks.

— Givosiran: hold or reduce if ALT >3× ULN.

Elderly patients:

Renal impairment:

Hepatic impairment:

Step 3 management: For an AIP patient ≥50, schedule HCC surveillance ultrasound every 6 months alongside ALT and AFP. This is a high-yield maintenance order on CCS.

Key distinction: AIP-related CKD is distinct from acute kidney injury during an attack, which is usually pre-renal from vomiting/dehydration and reverses with hydration.

Board pearl: Long-term AIP carries triple long-term risks — CKD, HTN, and HCC — all three must be on the surveillance checklist.

Special Populations — Pregnancy and Pediatrics

— Historically considered high-risk, but with modern management most pregnancies are uneventful.

— Attacks tend to occur in the first trimester (hormonal shifts, hyperemesis-induced fasting); attacks decline in the second and third trimesters.

— Hyperemesis gravidarum can trigger attacks via caloric deprivation — manage with ondansetron (safe), IV D10, and early nutritional support.

— Hemin is considered safe in pregnancy (category C, but extensive observational safety data); use full doses for acute attacks.

— Givosiran is NOT recommended in pregnancy (insufficient data, potential fetal hepatic ALAS1 effects); discontinue when planning conception.

— Avoid in pregnancy: ergometrine, methyldopa (porphyrinogenic), barbiturates; labetalol, nifedipine, methyldopa? — methyldopa is unsafe; use labetalol or nifedipine for hypertension.

— Delivery: regional anesthesia (epidural with bupivacaine) is safe; for general anesthesia use propofol + sevoflurane.

— AIP attacks before puberty are extremely rare; presentation in a child should prompt evaluation for ALA-dehydratase deficiency porphyria (autosomal recessive) or lead poisoning.

— Asymptomatic children of an affected parent: genetic testing is generally deferred until adolescence (autonomy and triggers irrelevant before puberty); some centers test earlier for anticipatory guidance.

— Counsel adolescents at puberty: avoid smoking, alcohol, crash diets, OCPs with progestin; choose copper IUD or levonorgestrel IUD for contraception (lower systemic progestin).

Pregnancy in AIP:

Pediatrics:

Lactation: Hemin is poorly absorbed orally — considered compatible with breastfeeding. Givosiran data are limited; avoid.

Step 3 management: A 26-year-old AIP woman desires contraception — recommend copper IUD (first choice) or levonorgestrel IUD; avoid combined OCPs and depot medroxyprogesterone.

Board pearl: Childhood-onset neurovisceral porphyria-like illness → think lead poisoning or ALAD-deficiency porphyria, not AIP.

Key distinction: Pregnancy does not contraindicate hemin; it does contraindicate givosiran.

Complications and Adverse Outcomes

— Respiratory failure from progressive motor neuropathy involving diaphragm and bulbar muscles — leading cause of attack mortality

— Status epilepticus — challenging because most first-line anticonvulsants (phenytoin, carbamazepine, valproate, phenobarbital) are porphyrinogenic and worsen the attack

— Severe hyponatremia (Na <120) with seizures; risk of osmotic demyelination syndrome if corrected too rapidly (>8 mEq/L/24 h)

— Cardiac arrhythmias from autonomic instability and electrolyte derangement

— Rhabdomyolysis from immobility/seizures, with secondary AKI

— Aspiration pneumonia from bulbar weakness

— Ileus and bowel pseudo-obstruction

— Chronic kidney disease (up to 50% of patients with recurrent attacks)

— Hypertension — present in 40–60% of AIP patients, often persists between attacks

— Hepatocellular carcinoma — risk increased ~35-fold; mandates surveillance

— Chronic motor neuropathy with residual weakness (foot drop, hand weakness) after severe attacks

— Chronic pain syndromes and opioid dependence — a major quality-of-life issue

— Depression, anxiety, suicidality — rates exceed population baseline; screen routinely

— Phlebitis from hemin → use central access for repeated dosing

— Iron overload from chronic hemin (each dose delivers ~22 mg iron)

— Hyperhomocysteinemia, ↑LFTs, ↑Cr from givosiran

Acute complications during an attack:

Long-term complications:

Iatrogenic complications:

Step 3 management: When admitting an AIP patient, place continuous telemetry, q4h NIF/VC, and Na monitoring q6h in the first 24 hours. These three orders catch the three deadliest complications.

Board pearl: The classic exam stem: AIP patient given phenytoin for a seizure → attack worsens → respiratory failure. The correct anticonvulsant was levetiracetam, gabapentin, or IV magnesium.

CCS pearl: Suicide risk in AIP is real — order psychiatric consultation and PHQ-9 at discharge.

When to Escalate Care — ICU, Consults, and Inpatient Triage

— Vital capacity <15 mL/kg or NIF less negative than −20 cmH₂O (impending respiratory failure)

— Bulbar dysfunction: dysphagia, dysarthria, weak cough

— Hyponatremia <120 mEq/L or symptomatic hyponatremia

— Status epilepticus or recurrent seizures

— Hemodynamic instability requiring vasoactive support

— Rapidly progressing motor weakness

— Encephalopathy with airway concerns

— Use propofol for induction (safe); avoid thiopental, etomidate, ketamine

— Succinylcholine and rocuronium are safe

— Maintenance with propofol infusion ± fentanyl; avoid prolonged sevoflurane if hepatic concerns

— Hematology or porphyria specialist: at admission for any moderate-severe attack

— Neurology: for seizures, progressive weakness, or unclear neurologic findings

— Hepatology: for HCC surveillance setup and consideration of transplant in recurrent disease

— Genetics: for HMBS sequencing and family cascade counseling

— Psychiatry: for acute psychosis, depression, or suicidality

— Gynecology/REI: for menstrually triggered attacks (GnRH agonist, IUD)

— Anesthesia: preoperative consult for any planned surgery

— Pain controllable with PRN IV opioids

— Tolerating PO carbohydrates

— Sodium ≥130 and stable

— No motor weakness, no respiratory compromise

— Normal mental status

ICU transfer criteria:

Intubation considerations:

Consultations to obtain (and when):

Floor management is acceptable when:

Step 3 management: On CCS, the sequence for a moderate attack: admit to telemetry floor → start IV D10 → order urine PBG → administer hemin 3 mg/kg IV daily × 4 → consult hematology and neurology → daily NIF/VC → repeat Na q6h → transition to PO once stable → discharge with porphyria clinic follow-up in 1–2 weeks.

Board pearl: Failure to escalate when VC is falling is a board-favored "what was the error" question.

CCS pearl: Re-evaluate the patient every 6–12 simulated hours in the first 48 h — the disease can shift rapidly from manageable to life-threatening.

Key Differentials — Same-Category Causes

— Hereditary coproporphyria (HCP): autosomal dominant CPO deficiency; 30% have photosensitive skin lesions; ↑fecal coproporphyrin III; milder attacks than AIP.

— Variegate porphyria (VP): autosomal dominant PPOX deficiency; high prevalence in South African Afrikaners; ~60% have cutaneous blistering on sun-exposed skin; plasma fluorescence peak at 626 nm is pathognomonic.

— ALA-dehydratase deficiency porphyria (ADP, Doss porphyria): autosomal recessive, very rare, presents in childhood, ↑↑ALA, normal PBG, ↑coproporphyrin III; mimics lead poisoning biochemically.

— Porphyria cutanea tarda (PCT): most common porphyria overall; photosensitive blistering, hypertrichosis, hyperpigmentation; associated with HCV, HIV, alcohol, hemochromatosis, estrogen; treatment: phlebotomy or low-dose hydroxychloroquine; no neurovisceral attacks.

— Erythropoietic protoporphyria (EPP): painful non-blistering photosensitivity in childhood; ↑protoporphyrin in RBCs; risk of cholestatic liver disease.

— Congenital erythropoietic porphyria (Günther disease): severe disfiguring photosensitivity from infancy; erythrodontia, hemolytic anemia; UROS deficiency.

— Neurovisceral attack only, no skin findings → AIP

— Attack + skin blistering → VP or HCP (check plasma 626 nm and fecal porphyrins)

— Skin blistering only, no attacks, alcohol/HCV → PCT

— Childhood painful photosensitivity → EPP

— Severe infantile photomutilation, hemolytic anemia → CEP

Other acute hepatic porphyrias (share neurovisceral attack phenotype; management is identical):

Cutaneous porphyrias (do NOT cause acute attacks — important to distinguish):

Key distinction (the porphyria sorting algorithm for Step 3):

Board pearl: Asking "does the patient have skin findings?" is the fastest fork in the porphyria differential.

Step 3 management: Once acute hepatic porphyria is biochemically confirmed (↑PBG, ↑ALA), acute management is identical regardless of subtype — hemin and trigger removal. Subtyping matters for long-term counseling and family screening.

Key Differentials — Other-Category Causes

— Acute intermittent porphyria is famously diagnosed only after multiple negative abdominal explorations for appendicitis, cholecystitis, mesenteric ischemia, ovarian torsion, ectopic pregnancy, pancreatitis, SBO, perforated viscus. Lab and imaging negativity in the face of severe pain should prompt urine PBG.

— Familial Mediterranean fever: recurrent self-limited abdominal pain with fever, ethnicity clues, elevated CRP/SAA.

— Hereditary angioedema: recurrent abdominal pain from bowel-wall edema; low C4, low C1-INH.

— Guillain-Barré syndrome: ascending, distal-to-proximal weakness with areflexia, post-infectious; CSF: albuminocytologic dissociation. AIP weakness is proximal-upper-extremity-predominant with preserved reflexes early.

— Lead poisoning: abdominal pain, motor neuropathy, anemia with basophilic stippling, gingival lead line, exposure history (renovation, occupation); ↑↑ ALA, normal or mildly ↑ PBG, ↑ZPP, elevated blood lead.

— Heavy metal toxicity (arsenic, thallium, mercury): sensorimotor neuropathy, GI symptoms — 24-h urine heavy metals.

— Vasculitis (PAN, GPA): abdominal pain, neuropathy, multisystem; ANCA, biopsy.

— Thyroid storm: tachycardia, agitation, abdominal pain, hyponatremia — check TSH/free T4.

— Munchausen/factitious disorder, somatic symptom disorder, opioid-seeking behavior — AIP is frequently misdiagnosed as these. The discriminating feature: objective signs — tachycardia, hyponatremia, dark urine, elevated PBG.

— Sympathomimetic intoxication (cocaine, amphetamine, MDMA): autonomic surge, agitation.

— Serotonin syndrome / NMS: autonomic instability, rigidity, hyperthermia, medication clues.

— Diabetic ketoacidosis, adrenal crisis, pheochromocytoma: all on the differential for autonomic + abdominal symptoms.

Surgical/GI mimics of the abdominal pain:

Neurologic mimics:

Psychiatric mimics:

Toxic/metabolic mimics:

Key distinction: A tachycardic, hyponatremic, agitated young woman with red urine and a negative CT abdomen = AIP until proven otherwise. The presence of objective tachycardia and hyponatremia is what differentiates AIP from purely functional disorders.

Board pearl: Lead poisoning is the #1 metabolic mimic of AIP — always check a lead level when evaluating possible porphyria.

Secondary Prevention, Discharge Medications, Long-Term Plan

— Print the porphyria-safe drug list (American Porphyria Foundation; drugs-porphyria.org) and review every chronic medication

— Replace unsafe drugs:

· Carbamazepine/valproate/phenytoin → levetiracetam or gabapentin

· Combined OCP → copper IUD or levonorgestrel IUD

· Rifampin (for TB/MAC) → individualized; consult ID

· Sulfa antibiotics → alternative based on indication

· Statins: atorvastatin and rosuvastatin are generally safe; pravastatin preferred by some

· PPIs: omeprazole and pantoprazole are safe

· Beta-blockers: propranolol, atenolol, labetalol all safe and useful for residual HTN

— Trigger avoidance counseling: regular meals, avoid fasting/crash diets, no alcohol, no smoking, stress management, sleep hygiene

— Carbohydrate-rich diet (~55–60% carbs, ≥300 g/day); avoid ketogenic and very-low-carb diets

— Medic-alert bracelet stating "Acute Intermittent Porphyria — avoid porphyrinogenic drugs"

— Patient-held medication card with safe/unsafe lists for ED visits

Discharge medication reconciliation is THE highest-yield Step 3 task for AIP:

Long-term prevention strategy:

For patients with ≥2 attacks/year: initiate givosiran 2.5 mg/kg SC monthly

For menstrually triggered attacks: trial GnRH agonist (leuprolide) with add-back estrogen, or levonorgestrel IUD

Hypertension management: target <130/80; first-line ACEi/ARB (safe and renoprotective)

Vaccinations: annual influenza, COVID, pneumococcal, hepatitis A and B (HCC risk + liver protection)

Step 3 management: At discharge: (1) safe-drug list reviewed, (2) porphyria specialist follow-up in 1–2 weeks, (3) genetic counseling referral, (4) medic-alert bracelet ordered, (5) depression screen, (6) HCC surveillance schedule established.

Board pearl: The single most cost-effective intervention is family cascade genetic testing — identifying asymptomatic carriers prevents future attacks via early trigger counseling.

Key distinction: Hemin = attack rescue; givosiran, GnRH, lifestyle = prevention.

Follow-Up, Monitoring Parameters, and Counseling

— 1–2 weeks: porphyria specialist or hematology — review attack triggers, medication list, neurologic recovery

— 1 month: PCP — BP check, mood screen, medication adherence

— 3 months: labs — CBC, CMP, LFTs, ferritin (if hemin used), urine PBG/ALA (for baseline)

— 6 months: repeat ferritin if recurrent hemin, liver US + AFP if age ≥50 or established AIP

— Annual: comprehensive review — eGFR, urine albumin/creatinine, BP, HCC screen, depression screen, contraception review

— LFTs monthly × 6 months, then every 3–6 months

— Serum creatinine and eGFR every 3 months

— Homocysteine, B6, B12, folate at baseline and periodically; supplement as needed

— Lipase if abdominal pain (rare pancreatitis)

— Motor recovery occurs over weeks to many months; some residual weakness may persist

— Physical therapy and occupational therapy referrals for ongoing weakness

— Foot drop: orthotics

— Realistic expectations reduce frustration and depression

— Screen for depression (PHQ-9), anxiety (GAD-7), and suicidality at every visit

— AIP carries a 2–3× increased suicide risk — low threshold for psychiatric referral

— SSRIs: sertraline, citalopram are generally considered safe; avoid fluoxetine in some lists (variable evidence)

— Offer HMBS genetic testing to all first-degree relatives (siblings, children, parents)

— Asymptomatic carriers: counsel on trigger avoidance; no prophylactic treatment indicated unless attacks occur

— Reproductive counseling: 50% transmission risk per child; preimplantation genetic diagnosis available

Post-discharge cadence:

Givosiran monitoring (if used):

Neuropathy recovery counseling:

Mental health:

Family counseling:

Step 3 management: At every follow-up, re-review the medication list against the porphyria-safe database — new prescriptions from other providers are the #1 cause of breakthrough attacks.

Board pearl: Patients should carry an emergency card listing diagnosis and unsafe drugs; this is a board-favored discharge teaching item.

CCS pearl: Document "patient counseled on trigger avoidance: fasting, alcohol, unsafe medications" — earns CCS credit.

Ethical, Legal, and Patient Safety Considerations

— Adult first-degree relatives of an AIP proband should be offered HMBS sequencing with pre-test genetic counseling. Discuss implications for insurance (GINA protects health insurance and employment but NOT life, disability, or long-term-care insurance).

— Pediatric testing of asymptomatic minors is generally deferred until adolescence when triggers (alcohol, OCPs, smoking) become relevant, respecting the child's future autonomy. Exception: families/clinicians may test earlier if it changes management.

— Prenatal and preimplantation testing are available; discuss nondirectively.

— A patient in acute AIP attack with confusion or psychosis may lack decision-making capacity. Use surrogate decision-making for hemin administration and IV access. Document capacity assessment.

— Liver transplant consent requires extensive counseling on lifelong immunosuppression vs. continued attacks — involve transplant social work and ethics if needed.

— Implement EHR allergy/alert entry of "Acute Intermittent Porphyria" that triggers warnings for unsafe drugs (phenytoin, sulfa, rifampin, carbamazepine, etc.)

— Medication reconciliation at every transition of care (admission, transfer, discharge) — porphyrinogenic drugs are a leading cause of preventable readmission

— Pharmacist-led review at admission is high-yield

— Discharge to a SNF or rehab where staff are unfamiliar with AIP: provide written drug-avoidance list and direct contact for the porphyria specialist

— ED-to-floor handoff: explicitly communicate the diagnosis and avoid-list

— PCP handoff: include the HMBS variant, attack history, and monitoring plan

— Driving safety: patients with active neuropathy, recent seizures, or psychiatric instability should not drive — state laws vary on physician reporting of seizures (mandatory in CA, NJ, PA, DE, NV, OR; "should report" elsewhere). Counsel and document.

— Occupational risks: pilots, commercial drivers, military — disclosure obligations may apply.

Genetic testing ethics:

Informed consent edge cases:

Patient safety — medication errors are the #1 iatrogenic harm:

Transition-of-care risks:

Mandatory reporting/disclosure:

Step 3 management: A patient with AIP who had a recent seizure asks if they can drive home — answer is no driving until seizure-free per state law (typically 3–12 months) and provide written instructions.

Board pearl: GINA does not cover life, disability, or long-term-care insurance — disclose this limitation before genetic testing.

High-Yield Associations and Rapid-Fire Clinical Facts

Enzyme defect: HMBS (PBG deaminase), 3rd enzyme in heme synthesis; autosomal dominant

Accumulated toxins: ALA and PBG (both neurotoxic)

Rate-limiting enzyme upregulated in attacks: hepatic ALAS1 (induced by CYP450-inducing drugs, fasting, hormones)

Hallmark trio: abdominal pain + autonomic instability + neuropsychiatric symptoms

Demographics: young women 18–45; rare before puberty

Skin involvement: NONE in AIP (skin findings → VP, HCP, or PCT)

Urine color: port-wine on standing (PBG → porphobilin oxidation)

Sodium: hyponatremia (SIADH-pattern) common

Neuropathy pattern: proximal motor, upper extremity > lower, reflexes preserved early

Best initial test: spot urine PBG during attack

Confirmatory test: HMBS gene sequencing

First-line acute treatment: IV hemin 3–4 mg/kg/day × 4 days, reconstituted in albumin

Bridge treatment: IV D10 (≥300 g glucose/day)

Prophylaxis for recurrent attacks: givosiran 2.5 mg/kg SC monthly

Cure: liver transplant

Top unsafe drugs: phenobarbital, phenytoin, carbamazepine, valproate, rifampin, sulfonamides, OCPs, progesterone, metoclopramide, griseofulvin, ergots, alcohol

Safe analgesics: morphine, fentanyl, hydromorphone, acetaminophen, gabapentin

Safe anesthesia: propofol, sevoflurane, isoflurane, succinylcholine, rocuronium, vecuronium, fentanyl

Safe antiemetic: ondansetron

Safe seizure drug: levetiracetam, gabapentin, magnesium

Safe contraception: copper IUD (first-line), levonorgestrel IUD

Long-term risks: CKD, HTN, HCC (~35× risk), chronic pain, depression

HCC surveillance: liver US + AFP every 6 months in patients ≥50 or long-standing AIP

Lead poisoning vs AIP: lead → ↑↑ALA, normal/mildly ↑PBG, ↑ZPP, lead level elevated

Variegate porphyria clue: plasma fluorescence peak at 626 nm, South African Afrikaner ancestry

Genetics rule: offer HMBS testing to all first-degree relatives

CCS pearl: Always co-order urine PBG + ALA + total porphyrins on the same sample.

Board pearl: A young woman with recurrent abdominal pain, multiple negative laparotomies, hyponatremia, and tachycardia — answer is urine PBG.

Board Question Stem Patterns

Stem 1 — The classic miss: A 28-year-old woman presents with her fourth ED visit in 18 months for severe diffuse abdominal pain. Prior workups including CT, ultrasound, and laparoscopy were unrevealing. She is tachycardic (118), BP 158/96, and her urine is noted to be dark red by the nurse. Na 126. → Next best test: urine porphobilinogen (PBG).

Stem 2 — The trigger: A 32-year-old woman with known AIP starts a new medication and develops severe abdominal pain, vomiting, and confusion within days. Which medication? → Phenobarbital, phenytoin, rifampin, carbamazepine, or sulfamethoxazole (any CYP450-inducer or porphyrinogenic drug).

Stem 3 — Treatment choice: A 30-year-old with confirmed AIP attack has Na 124, severe pain, and proximal arm weakness. Best treatment? → IV hemin 3–4 mg/kg/day × 4 days (not glucose alone — that's for mild attacks).

Stem 4 — The wrong seizure drug: AIP patient seizes; intern gives phenytoin; patient deteriorates. What was the error? → Phenytoin is porphyrinogenic; should have used levetiracetam, gabapentin, or magnesium.

Stem 5 — The mimic: A 40-year-old house renovator presents with abdominal pain, wrist drop, and microcytic anemia with basophilic stippling. Urine ALA elevated, PBG normal. → Lead poisoning, not AIP. Treat with chelation (succimer or EDTA).

Stem 6 — Contraception: A 26-year-old woman with AIP wants contraception. Best option? → Copper IUD (avoid combined OCPs and DMPA).

Stem 7 — Family screening: A 35-year-old man newly diagnosed with AIP — what do you offer family? → HMBS gene sequencing for all first-degree relatives with pre-test counseling.

Stem 8 — Long-term surveillance: A 52-year-old with AIP for 20 years — what surveillance? → Liver ultrasound + AFP every 6 months for HCC.

Stem 9 — Pregnancy: AIP patient in first trimester with hyperemesis develops an attack. Treatment? → IV D10, ondansetron, and IV hemin — hemin is acceptable in pregnancy.

Stem 10 — The cure: AIP patient with >6 attacks/year despite hemin and givosiran — definitive therapy? → Liver transplantation.

Stem 11 — Skin clue: AIP-like attack + photosensitive vesicles on hands → variegate porphyria (plasma 626 nm peak).

Board pearl: Any vignette with young woman + recurrent abdominal pain + hyponatremia + tachycardia + reddish urine + multiple negative imaging → answer is urine PBG, then hemin.

One-Line Recap

Acute intermittent porphyria is a hepatic heme-synthesis defect (HMBS deficiency) presenting in young women with recurrent neurovisceral attacks of abdominal pain, autonomic instability, neuropsychiatric symptoms, and hyponatremia — diagnosed by elevated urine PBG during an attack and treated with IV hemin plus trigger removal.

Recognize: young woman, recurrent abdominal pain with negative imaging, tachycardia, hyponatremia, red/port-wine urine, proximal motor weakness, psychiatric symptoms — send urine PBG before the attack resolves.

Treat acutely: IV hemin 3–4 mg/kg/day × 4 days (reconstituted in albumin, central line preferred) is first-line; IV D10 ≥300 g/day is a bridge or for mild attacks; use only porphyria-safe drugs for pain (morphine), nausea (ondansetron), seizures (levetiracetam, magnesium), and HTN (propranolol, labetalol); stop all porphyrinogenic drugs (phenytoin, carbamazepine, valproate, phenobarbital, rifampin, sulfa, OCPs, metoclopramide).

Prevent recurrence: trigger avoidance (no fasting, no alcohol, no smoking, carb-rich diet, safe-drug list, medic-alert bracelet), givosiran 2.5 mg/kg SC monthly for ≥2 attacks/year, GnRH agonist or levonorgestrel IUD for menstrual triggers, and liver transplant for refractory disease.

Long-term: annual eGFR, BP, depression screen; HCC surveillance with liver US + AFP every 6 months in patients ≥50 or long-standing disease; HMBS genetic testing for all first-degree relatives with pre-test counseling about GINA's limits.

Step 3 management: the single most important discharge action is medication reconciliation against the porphyria-safe drug database — porphyrinogenic prescriptions from outside providers are the leading cause of preventable readmission and the most common board-tested error.