Methylmalonic Acidemia
Etiology:
- deficiency of one of a few possible enzymes which causes an accumulation
of methylmalonic acid and its precursors.
- one of the enzymes requires adenosyl-cobalamin, a metabolite of vitamin
B12, as a coenzyme.
Presentation:
- neonatal period with ketosis, acidosis, hyperammonemia, neutropenia, coma,
and death.
- may present later in life with failure to thrive, hypotonia, and
developmental delay.
- some may have characteristic facial features which include a triangular
mouth and high forehead.
Treatment:
- acute attacks – treatment includes rehydration, correction of acidosis,
and prevention of catabolic state by provision of adequate calories through
parenteral hyperalimentation. Large doses of vitamin B12 may be used.
- long term treatment consists of a low-protein diet, and administration of
L-carnitine, and vitamin B12
- nursing vegan mothers must be given added vitamin B12 to prevent methylmalonic acidemia in their infants
CHLA Board Review 2005