Learn / FMK
Every FMK condition
299 diseases, deficiencies, toxicities and drug mechanisms harvested from every FMK deck — the ones sprinkled through a single bullet as much as the ones with their own slide. Pick what you're given and what you have to name, or let it cycle; distractors come from the same category so you have to discriminate (hypoketotic vs. ketotic hypoglycemia, which GSD, which urea-cycle enzyme…). Every answer shows the whole card with the lecture and slide.
Heme · FMK 08.4
Porphyria cutanea tarda (PCT) Acquired / not inherited
Defect / target: Uroporphyrinogen decarboxylase (UROD) - step 5 (cytosol)
Mechanism: Severe (often acquired) deficiency of hepatic UROD prevents decarboxylation of uroporphyrinogen III to coproporphyrinogen III; accumulated uroporphyrin is cyclic and photoactive (Soret band), producing skin damage on light exposure without neurovisceral attacks.
↑ Accumulates: Uroporphyrin(ogen) in liver, plasma, urine and skin· ↓ Deficient: Coproporphyrinogen III and heme
Presentation: Most common porphyria; onset 4th-5th decade; painful blisters and skin fragility on sun-exposed skin (dorsal hands), hyperpigmentation, hypertrichosis, tea/red-brown urine; associated with hepatitis C, alcohol, estrogen, iron overload/hemochromatosis, phenytoin; no acute attacks
Labs: Markedly elevated urinary uroporphyrin; urine fluoresces coral-pink under Wood's (UV) lamp
Treatment: Therapeutic phlebotomy (reduces hepatic iron), low-dose hydroxychloroquine, treat HCV, avoid alcohol/estrogen, sun protection
Chronic hepatic porphyria; after ring closure = cutaneous; PCT = hepatic/adult/blistering vs EPP = marrow/childhood/non-blistering
Learn the mechanism: Heme synthesis (porphyrias) →
FMK 08.4 Heme Metabolism · slide 11, 14, 17, 18; handout