Dear Dr. Cannell:
For what it’s worth, I want to let you know that during the “Great Depression” of the 1930’s one of my cousins had rickets, which caused his legs to bow. My cousin was the third child in a large Indiana marginal farm family.
It seems logical that as a farm kid my cousin received as much summer sunshine as his siblings. My mother gave me cod liver oil and I remember hearing her remark that my aunt and uncle didn’t know about things like cod liver oil and that was the reason my cousin had rickets.
It’s puzzling to me why one member of eight or ten siblings (I’ve lost count) would have rickets and the others not unless something happened (or didn’t happed) during pregnancy. I doubt that an anecdotal story with few details can add to your research but who knows?
When you ask why someone gets a disease and someone else does not, you have to ask the same question about all diseases. Why do some smokers get bladders cancer, others heart disease, and other live to be 99? Why do some vitamin D deficient people get lupus, while others get heart disease and others seem fine? It is probably genetic tendency.
When only one child in a large farm family in Indiana gets rickets, several thoughts come to mind. Oddly, one of the first clues about the sun’s role in rickets was the 3:1 rural (outside more) to urban (outside less) ratio (the same ratio as in autism). Still, the answer could be as easy as perhaps your cousin stayed inside more than his siblings, despite living in a rural environment. Perhaps he had poor calcium intake (rickets can occur because of poor calcium intake, not just vitamin D deficiency). Perhaps he had one of the rare genetic forms of rickets.
I’d need to know more about the course of his disease, such as his treatment regimen and his response, but, if it was vitamin D deficient rickets, my guess is that for some reason he avoided the sun. In the 1930s, the government had not yet fortified cow’s milk with vitamin D, so not drinking milk as a cause of his rickets is out. Another possibility is that he was just unlucky, genetically. Few people know that vitamin D levels have a strong genetic component, at least in the winter. So your cousin may just have been born with a genetically determined low 25(OH)D level.
Karohl C, Su S, Kumari M, Tangpricha V, Veledar E, Vaccarino V, Raggi P. Heritability and seasonal variability of vitamin D concentrations in male twins. Am J Clin Nutr. 2010 Dec;92(6):1393-8. Epub 2010 Oct 13.