A family in which two male infants died with spastic dementia, seizures, and defective hair development is described and is compared with a very similar family reported recently. Despite the marked similarity in the clinical findings and the pattern of inheritance in the two families, the biochemical findings differed, providing the impetus for this report. Whereas previously Menkes, et al, found elevated levels of glutamic acid in the blood of two of five affected boys, all of the plasma and urinary amino acid values in the patient reported here were normal. Whether observations reported here amid those of Menkes should be interpreted to indicate the existence of two different diseases with very similar clinical features, or whether the glutamic acidemia is an inconsistent epiphenomenon in a single inborn error of metabolism must be considered.