Investigators at Wakayama Medical University, Japan, report the neuroimaging features soon after birth in 2 siblings with molybdenum cofactor deficiency (MoCoD) type A. Seizures occurred soon after birth. Brain ultrasound revealed subcortical multicystic lesions in the frontal white matter, and brain MRI at 4-24 hours after birth showed restricted diffusion on diffusion-weighted images, with severe atrophy of the entire cortex within 1 month. The corpus callosum was absent or underdeveloped in both infants. 
COMMENTARY. MoCo is a coenzyme common to sulfite oxidase, xanthine dehydrogenase and aldehyde oxidase. Encephalopathy in MoCoD may result from isolated sulfite oxidase deficiency. MoCoD presents with intractable seizures in the neonatal period and MRI findings are similar to those of hypoxic ischemic encephalopathy (HIE). Since MoCoD progresses rapidly after birth, early diagnosis suspected by MRI findings can be confirmed with low plasma uric acid, positive sulfite dipstick in fresh urine, and elevated urine and plasma s-sulfocysteine. In infants with HIE these markers are absent and the plasma uric acid is elevated. On diffusion weighted imaging within 1 week after birth, patients with HIE show an increased signal in all cortical and subcortical areas, whereas in patients with MoCoD these findings are not uniform.
In addition to HIE, infants with MoCoD may present with neonatal hyperekplexia, unresponsive to clonazepam , and as pyridoxine-dependent epilepsy . Two siblings with pyridoxine-responsive seizures and increased urinary excretion of a-AASA were diagnosed with MoCoD and a mutation in the MOCS2 gene. A trial of pyridoxine is recommended in patients with MoCo or sulfite oxidase deficiencies .