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.
Nucleotide · FMK 07.1
Hereditary orotic aciduria (UMP synthase deficiency) Autosomal recessive
Defect / target: UMP synthase (de novo pyrimidine synthesis)
Mechanism: Orotate cannot be converted to UMP, so orotic acid accumulates and spills into urine while the cell is starved of pyrimidine nucleotides for RNA/DNA synthesis, hitting rapidly dividing bone marrow hardest; the defect is entirely within pyrimidine synthesis, so ammonia handling is normal.
↑ Accumulates: Orotic acid· ↓ Deficient: UMP / pyrimidines
Presentation: Megaloblastic anemia unresponsive to B12/folate, failure to thrive / poor growth in infancy, orotic acid crystals in urine, normal ammonia
Labs: Massive orotic aciduria with orotic acid crystals; megaloblastic anemia; NORMAL serum ammonia (contrast with OTC deficiency)
Treatment: Uridine
Orotic aciduria + hyperammonemia = OTC; orotic aciduria without hyperammonemia + megaloblastic anemia = UMP synthase deficiency
Learn the mechanism: Pyrimidine synthesis (& thymidylate) →
FMK 07.1 Amino Acid Metabolism I; FMK 08.1 Nucleic Acid Metabolism · slide 07.1: 15; 08.1: 22, 26, 27, 28