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
X-linked sideroblastic anemia X-linked recessive
Defect / target: ALAS2 (erythroid-specific ALA synthase; X-linked gene)
Mechanism: Loss of erythroid ALA synthase activity blocks the first step of heme synthesis in marrow precursors, so iron delivered to mitochondria cannot be incorporated into heme and accumulates as ring sideroblasts.
↑ Accumulates: Iron in erythroblast mitochondria (ring sideroblasts)· ↓ Deficient: Heme / hemoglobin in erythroid cells
Presentation: Microcytic anemia, iron overload; a hematology disorder, NOT a porphyria
Labs: Ring sideroblasts on marrow Prussian-blue stain, microcytic anemia, elevated iron/ferritin
Treatment: Pyridoxine (B6) trial, since ALAS is PLP-dependent
ALAS2 = erythroid, X-linked, iron-regulated (IRE/IRP); ALAS1 = liver, heme-repressed, drug-induced
Learn the mechanism: Heme synthesis (porphyrias) →
FMK 08.4 Heme Metabolism · slide 9