3-Hydroxyisobutyric acidemia. 3-hydroxyisobutyrate dehydrogenase deficiency
Incidence
Very rare. Six infants reported. It is a disorder of valine catabolism.
Clinical Characteristics
It is usually fatal when presenting neonatally. There is hypotonia, FTT, metabolic acidosis (lactic acidosis). Reccurrent vomiting and lethargy. There is intrauterine growth retardation (IGR), microcephaly, severe developmental delay and dysmorphic features such as triangular face, short lopped forehead, hypoplastic orbital ridge, narrow bitemporal diameter, epicanthus, prominent filtrum, micrognatia. On CT scan there is lyssencephaly or pachygyria or polymicrogyria, agenesis of the corpus callosum, cerebellar hypoplasia, dense calcifications of frontal lobes and subependimal regions. Pts excrete large amounts of 3-hydroxyisobutyric acid in urine.
Precipitants
Probably high protein diet may trigger a crisis or make worse the clinical course of the disease.
Provocation Tests
no
Diagnostic Procedures
EB-F, GC/MS for organic acids in urine. There is large amounts of 3-hydroxyisobutyric acid in urine.