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 08.1
Lesch-Nyhan syndrome X-linked recessive
Defect / target: Complete deficiency of HGPRT (hypoxanthine-guanine phosphoribosyltransferase), the purine salvage enzyme
Mechanism: Hypoxanthine and guanine cannot be salvaged to IMP/GMP, so they accumulate and are degraded to uric acid; unconsumed PRPP stays elevated and IMP/GMP fall, both disinhibiting GPAT and driving even more de novo purine synthesis, compounding uric acid production; brain, marrow and RBCs rely on salvage and cannot compensate.
↑ Accumulates: Hypoxanthine, guanine, PRPP, uric acid· ↓ Deficient: Salvaged IMP and GMP (in salvage-dependent tissues: brain, bone marrow, erythrocytes)
Presentation: Compulsive self-mutilation (lip and finger biting), choreoathetosis, spasticity, cognitive and developmental deficits, gouty arthritis and urolithiasis even in young children
Labs: Markedly elevated uric acid (serum and urine)
Treatment: Allopurinol (addresses urate/gout only, not the neurologic features)
Ethan, age 3, biting his fingers and lips until they bleed with high uric acid — one missing enzyme causes both gout AND self-injury. Salvage matters most where de novo synthesis is limited (brain, marrow).
Learn the mechanism: Purine synthesis & salvage →
FMK 08.1 Nucleic Acid Metabolism · slide 2, 13, 14, 28, 29