Investigations on the prevalence and characteristics of adolescent rickets in South African interracial schoolchild populations in the Transvaal

Abstract

Certain skeletal abnormalities of legs and chest are normally regarded as sequelae of rickets, '. and due to vitamin D deficiency. In seeking to throw light on the prevalence and characteristics of these abnormalities in South African schoolchildren, prior to and during adolescence, it was deemed important, firstly, to assess prevalences of these abnormalities and secondly, to investigate their relationship to vitamin D status. Hence, prevalences of bowing and knock knee, and of chest abnormalities such as Harrison's sulcus, pigeon breast, etc., were determined, and dietary, radiological and biochemical studies were made. Appropriate measurements in the four ethnic groups (Bantu, Coloured, Indian, White) revealed that bowing and knock knee were unexpectedly common, affecting a fifth, and a third of all children, respectively. Prevalences were not obviously affected by a higher dietary intake of vitamin D, rural-urban location, habitual exposure to radiation, or skin pigmentation. Prevalences of chest abnormalities, Harrison's sulcus, 0-5%; pigeon breast, 0-2%, also appeared unrelated to these factors. An important finding was that with age, bowing frequency increased mainly during the adolescent growth spurt. Prevalence of knock knee was little affected by age, but increased markedly with body mass. There was no age trend with prevalences of chest abnormalities. Since leg abnormalities were approximately equally common in groups accustomed to a high compared with a low dietary intake of vitamin D, it is inferred that a primary deficiency of vitamin D is not the causal factor. The most plausable explanation is that a secondary deficiency of vitamin D is involved, arising from an impairment in metabolic availability. However, the possibilities cannot be excluded that the leg abnormalities; in large measure, are physiological variants, or that an unknown factor or factors may bear, or share, in the responsibility. What is urgently required is an attempt to correlate individual vitamin D status of schoolchildren during their pubertal growth spurt; also the carrying out of long-term studies from birth to post-adolescence , of the type already undertaken.