Subependymal cysts were identified by cranial ultrasound and confirmed by MRI in an infant with holocarboxylase synthetase (HCS) deficiency, presenting with lactic acidosis, shock, and hypertonia, and responsive to biotin therapy (10mg daily), in a report from Devos Children’s Hospital, Grand Rapids, MI. At delivery the infant had apnea and bradycardia, and Apgars were 7 and 8. Within hours she developed tachypnea, fever, and shock. Laboratory studies showed metabolic acidosis, hypoglycemia, lactic acidosis, and elevated pyruvate and ammonia. Urinary organic acid assays revealed increased 3-hydroxyisovaleric acid, 3-methyl-crotonoylglycine, and methylcitric acid, diagnostic of multiple carboxylase deficiency. Treatment with bicarbonate and biotin was followed by remission of symptoms and a normal development at 14 month follow-up. MRI at age 6 months showed resolution of the bilateral subependymal cysts and normal myelination. 
COMMENT. Subependymal cysts uncovered by cranial ultrasound in a sick neonate require investigation of possible metabolic disorders. Prompt diagnosis and specific therapy can prevent fatalities and permit normal development.
Glutaric aciduria type 1 is cited in association with cerebral arachnoid cysts  and L-2-hydroxyglutaric aciduria is reported in 6 Portuguese children presenting with mental deficiency, cerebellar ataxia, progressive macrocephaly and seizures . A thalamic tumor, a diffuse fibrillary astrocytoma, was found in one of these cases, the second in the literature described with hydroxyglutaric aciduria.