Intracranial Calcification Associated with 3-Methylcrotonyl-CoA Carboxylase Deficiency.

3-methylcrotonyl-CoA carboxylase (3-MCC) deficiency is the most frequent organic aciduria detected in newborn screening programs. It demonstrates a variable heterogeneous clinical phenotype, ranging from neonatal onset with severe neurological disorders to asymptomatic adult forms. Herein, we report the first 2 related cases of 3-MCC deficiency presenting with intracranial calcification in the literature. A girl and a boy aged 3 years, 9 months and 4 years were included in the study. The main clinical manifestations were acquired microcephaly, global developmental delay, intractable seizures, mild feeding difficulty, and intermittent dystonic contractions. On physical and neurological examinations, their weights, heights, and head circumferences were below the 3rd percentile, they had acquired microcephaly, truncal hypotonia, upper and lower limb spasticity, hyperreflexia, positive bilateral Babinski signs, and clonus. The detailed biochemical and metabolic tests were unremarkable, except blood 3-hydroxyisovalerylcarnitine (C5OH) was slightly increased in case 1. Cranial computed tomography demonstrated mild cerebral and cerebellar atrophy as well as bilateral periventricular and thalamic calcifications in both cases. We identified a homozygous mutation of c.1015G>A (p.V339M) in the