Homocystinuria: a New Inborn Error of Metabolism Associated with Mental Deficiency.

It is now becoming generally noted that many diseases of hitherto unknown aetiology are due to inborn errors of metabolism in the sense in which Garrod (1923) used this term. Although these diseases cover the whole of medicine it has been particularly gratifying to note that mental disease, especially mental deficiency which currently is responsible for one of our main medical problems, has been especially involved in these recent discoveries. In particular, a number of inborn errors of metabolism causing mental disease have been described recently in which the disorder concerned the metabolism of one or more of the amino acids. Of these, in addition to phenylketonuria which was described by Folling in 1934, we now have Haitnup disease (Baron, Dent, Harris, Hart and Jepson, 1956), the occulo-cerebro-renal syndrome (Lowe, Terrey and MacLachlan, 1952; Denys, Corbeel, Eggermont and Malbrain, 1958), cystathioninuria (Harris, Penrose and Thomas, 1959), argininosuccinic aciduria (Allan, Cusworth, Dent and Wilson, 1958; Dent, 1959), maple syrup urine disease (Dancis, Levitz and Westall, 1960; Dent and Westall, 1961), hyperglycinaemia (Childs, Nyhan, Borden, Bard and Cooke, 1961), familial hyperprolinaemia (Schafer, Scriver and Efron, 1962) and citrullinuria (McMurray, Mohyuddin, Rossiter, Rathbun, Valentine, Koegler and Zarfas, 1962). Another gross disorder of amino acid metabolism involving histidine (Ghadimi, Partington and Hunter, 1961; Auerbach, Di George, Baldridge, Tourtellotte and Brigham, 1962) is also described but without as yet very tangible clinical consequences, two of the three affected children showing only a mild speech defect. It does not seem too much to