Methylmalonic Acidemia (MMA)

What this deck covers

Methylmalonic Acidemia (MMA) in twelve clinical teaching cases with worked explanations. Each case gives you a clinical vignette, four options, the correct answer, and an explanation of why each of the other three is wrong.

Diagnoses and management options tested

Across the twelve cases you are asked to choose between options such as: Iron deficiency anaemia, Folic acid deficiency, Markedly elevated methylmalonic acid and methylcitrate, Elevated orotic acid and citrulline, Elevated isovalerylglycine and 3-hydroxyisovaleric acid, Propionyl-CoA carboxylase deficiency, Biotinidase deficiency impairing multiple carboxylases, Elevated free carnitine (C0) with normal C3, Elevated isovalerylcarnitine (C5) with low C0, Elevated octanoylcarnitine (C8) with normal C3, Urine methylmalonic acid quantification by GC-MS, mut⁰ (MMUT gene, complete enzyme absence), mut⁻ (MMUT gene, partial residual activity), cblA (MMAA gene defect), cblB (MMAB gene defect), Administer intramuscular hydroxocobalamin and observe, Dilated cardiomyopathy, Progressive chronic kidney disease, Optic nerve atrophy, Hepatic cirrhosis.

Clinical pearls from this deck

• Catabolism is the enemy and glucose is the first weapon. High-rate dextrose halts the breakdown of amino acids and fat, which is what generates propionyl-CoA and methylmalonyl-CoA in the first place. Stabilisation comes before diagnosis in a crashing neonate.
• Macrocytic anaemia + markedly elevated homocysteine + NORMAL serum B12 + neurological signs is the cblC pattern. The MMACHC defect blocks intracellular cobalamin processing, crippling both adenosylcobalamin (so MMA rises) and methylcobalamin (so homocysteine rises).

The twelve worked cases in this deck, with the images and the full explanation of every option, are part of Pediatric Case Review membership. See what is included.

More from this system: all metabolic and genetic decks and question sets · pediatric reference values.