Observations on nicotinic acid therapy in Hartnup disease.

Nicotinamide deficiency is a well-recognized biochemical abnormality in untreated cases of Hartnup disease (Baron, Dent, Harris, Hart, and Jepson, 1956; de Laey, Hooft, Timmermans, and Snoeck, 1964).There is general agreement that nicotinamide or nicotinic acid therapy is effective in the prevention and cure of the pellagrinoid rash in these patients.There is also some evidence that nicotinic acid may be beneficial in the treatment of the neurological symptoms (Baron et al., 1956;Halvorsen and Halvorsen, 1963).In 1964 de Laey et al. reported that nicotinic acid therapy completely corrected the metabolic abnormalities in one patient under their study.This has never been observed in any other case reported in the literature.A confirmation of their observation is of primary importance, not only because nicotinic acid may be a curative treatment in Hartnup disease, but also because it may be a causal factor in the primary defect that has been demonstrated in the transport of tryptophan in these patients (Milne, Crawford, Girao, and Loughridge, 1960; Wong and Pillai, 1966).The present paper describes some biochemical observa- tions before and during intensive nicotinic acid therapy in two cases of Hartnup disease.The clinical and biochemical abnormalities in these two patients have been previously reported (Wong and Pillai, 1966).Materials and Methods Oral L-tryptophan loading tests were performed before and during oral nicotinic acid therapy.100 mg.L-tryptophan per kg.body weight was dissolved in orange squash and was given to the fasting patients in the moming.The patients were given a constant protein diet at regular meal times three days before and during the experiments.Similarly, oral L-tryptophan loading tests were performed in untreated normal children as controls.Heparinized venous blood was used for the estimation of tryptophan and amino acids.Plasma tryptophan was estimated by the method of Duggan