ELEVATED PLASMA GLUTAMATE LEVELS WITHOUT HYPOTHALAMIC LESIONS

Abstract

Three male infants have been reported with elevated plasma glutamate levels, mental retardation and brain atrophy. We have observed a fourth male infant with elevated plasma glutamate (10 X normal). CSF glutamate was normal. The infant was hypotonic without Moro, suck or grasp. His clinical course was complicated by seizures (not the “shuddering syndrome” type), intolerance to feedings, hypocalcemia, and hypernatremia. EEC was abnormal. Chromosomal analysis was normal. At death (53 days), moderately severe atrophy of the cerebral hemispheres with greater atrophy of the cerebellum and mildly dilated ventricles were noted. The hypothalamus was embedded in celloidin and serially sectioned at 40 u. Cellular morphology was normal throughout; no evidence of dendritic swelling, pyknotic nuclei or other manifestations of the lesion induced by glutamate in the rodent were noted. The elevated plasma glutamate may represent a rare enzymatic abnormality of glutamate metabolism either directly or indirectly associated with mental retardation and cerebral atrophy. However, the infant's chronically elevated plasma glutamate levels were not associated with the type of gross hypothalamic lesions reported in the infant rodent with high glutamate levels. An oral glutamate challenge to the child's parents was given. The father showed an abnormal tolerance curve and reported the symptoms of the Chinese Restaurant Syndrome.