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.
Protein structure · FMK 06.1
Methemoglobinemia Acquired / not inherited
Defect / target: Oxidation of heme iron Fe²⁺→Fe³⁺: oxidizing drugs/toxins (nitrates in well water, certain local anesthetics, dapsone), congenital NADH–cytochrome b₅ reductase deficiency, or HbM globin variants that stabilize Fe³⁺
Mechanism: Ferric (Fe³⁺) methemoglobin cannot bind O₂ at all, so supplemental oxygen cannot be used by the blood that carries it.
↑ Accumulates: Methemoglobin (Fe³⁺ heme)· ↓ Deficient: Functional Fe²⁺ hemoglobin; NADH–cytochrome b₅ reductase (congenital form)
Presentation: Grey-blue cyanosis unresponsive to supplemental O₂, 'chocolate-brown' blood, normal-appearing lungs; classic infant after well-water (nitrate) formula
Labs: Chocolate-brown blood; cyanosis with normal pulse oximetry/lungs; methemoglobin level
Treatment: Methylene blue — accelerates enzymatic reduction of Fe³⁺ back to Fe²⁺
Fe²⁺ vs Fe³⁺: 'chocolate-brown' blood that extra O₂ won't fix
acquired (drug/toxin) or AR (cytochrome b₅ reductase deficiency); HbM variants AD
Learn the mechanism: Heme synthesis (porphyrias) →
FMK 06.1 Protein Structure & Function I; FMK 08.4 Heme Metabolism · slide 06.1: 2, 24, 26; 08.4: 6