[Secondary cystathioninuria due to vitamin B 6 deficiency in familial neuroblastoma]

In this study numerous amino acid analyses were performed in a family with increased incidence of tumors of the sympathetic nervous system. Since in 9 respectively 10 of a total of 13 surveyed persons an elevated urinary excretion of cystathionine was demonstrated with thin layer and column chromatographic methods, this constitutes the first report on cystathioninuria in familial neuroblastoma. Two family members also presented a homocystinuria in the spontaneously voided 24-hours urine. The only person whose plasma amino acids were analysed showed nearly normal levels. After oral loading with L-methionine the urinary excretion of cystathionine raised considerably. The different reaction of the two vitamin B6-dependent enzymes, cystathionine-synthetase and cystathionase, points at a different methionine induced sensitivity. The determination of pyridoxal phosphate and pyridoxal kinase detected a vitamin B6-deficiency, which corresponded well with an increased excretion of oxalic acid and a low normal urinary taurin excretion. Therefore these alterations of the amino acids are explained and thus urinary excretion of cystathionine can be interpreted as secondary cystathioninuria. Furthermore it was possible to provoke corresponding biochemical changes by oral administration of vitamin B6 such as reduction of the cystathioninuria and disappearance of the homocystinuria. In an infant the cystathioninuria could be observed over a period for 5 months, by which a transitory deficiency of the apoenzyme appears to be unlikely. The analysis of 24 hours urine samples of a gravida showed the persistance of cystathioninuria also during pregnancy. After radiation of a 5 year old girl with ganglioneuroblastoma an increase of the urinary cystathionine excretion and a first occurrence of homocystinuria was noted. These observations give rise to various considerations. The vitamin-B6-deficiency in familial neuroblastoma supports the assumption, that also the cystathioninuria in nonhereditary cases may be caused by vitamin-B6-deficiency. Since in this family the excretion of catecholamines was examined in a prior investigation a comparison of these two studies does not support the suggestion of a direct connection between the excretion of catecholamines and cystathioninuria, as it has been assumed to occur in sporadic neuroblastoma. The vitamin-B6-deficiency as seen in this family can also be considered in relation to tumor development. In the discussion about this possibility also the appearance of cystathioninuria in other tumors of early childhood is mentioned. Furthermore the relation of vitamin B6 to teratogenesis is commented on.