The disease, called for convenience after-the name of the family," H disease", occurred in a boy of 12, and there was evidence of it in 3 siblings. The parents were first cousins but were not affected. Direct dietary deficiency could not be invoked in the aetiology, although there was some response to nicotinic acid or nicotinamide. An extensive biochemical investigation was made. Excessive excretion of amino acids in the urine was the most characteristic feature, and was present also in the siblings; 11 amino acids were chiefly affected, others less so or not at all. The abnormality was of renal origin, plasma values for amino acids being normal. The pattern of indole excretion in the urine also was abnormal in all 4 subjects, and there was an excessive amount of protoporphyrin in the faeces.

It is suggested that the hereditary defect may be a disorder of tryptophan metabolism, by which a metabolic block exists somewhere on the path from tryptophan to nicotinic acid, but it is also thought possible that there may be a primary disorder of the amino acid transport procesess, leading to development of an abnormal gut flora which would distort the normal sequence of nicotinic acid metabolism. Other cases have been detected in the United Kingdom.-EM Hume.