Asian rickets and osteomalacia: patterns of parathyroid response in vitamin D deficiency.

We have seen personally more than IOO cases of rickets and osteomalacia in Asian immigrant patients during the past 6-8 years and we are satisfied that they arise simply on a basis of vitamin D deficiency. The present report is concerned principally with a more detailed study of thirtysne patients, aged 11-54 years. Our patients have been adult women, often pregnant at the time of diagnosis, and adolescents of both sexes. Clinically affected men are rare and a limited population survey showed little biochemical evidence of vitamin D deficiency in the adult male (Holmes, Enoch, Taylor & Jones, 1973). The calculated dietary intake of vitamin D in this immigrant population is low, but not necessarily less than that of the indigenous Caucasian population (Holmes et al. 1973) and the sexual difference in the incidence of overt bone disease cannot be explained on a dietary basis. It is considered illogical to invoke a widespread deleterious genetical abnormality in one of the world’s major populations and, in fact, there is no evidence of abnormal vitamin D metabolism in these individuals: they have a normal capacity to 25and ra-hydroxylate cholecalciferol (Mawer, 1974). From our clinical experience and from a limited epidemiological survey in the Punjab area of India (Hodgkin, Hine, Kay, Lumb & Stanbury, 1973) we are convinced that we are dealing with privational deficiency which we believe is caused primarily by inadequate exposure to sunshine. Wilson & Widdowson (1942) concluded that the development of vitamin D deficiency in India was due to lack of sunshine in a population group with a negligible dietary intake of vitamin D; they considered the high dietary intake of phytate to be irrelevant to the issue. Our limited experience of a cereal-eating group in the Punjab (Hodgkin et al. 1973) agrees with both conclusions. The latter suggestion is also supported by the fact that the vitamin D deficiency can be corrected, in British Asians foUowhg their normal social and dietary customs, by as little as I I pg ergocalciferol/d. Clinical experiences with these patients included the diagnosis of foetal (Russell & Hill, 1974) and neonatal rickets, and increased intracranial pressure, associated with a serum calcium concentration of 1.25 mmoV1, in a child of 7 months. But most patients had the commonplace classical features of rickets or osteomalacia of varying severity, and several presented with tetany. There are, however, certain features requiring particular comment.