The Re-emerging Burden of Rickets

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Robinson and co-workers report a retrospective, descriptive study of nutritional rickets presenting to 3 major teaching hospitals in Sydney, Australia from 1993 to 2003. Inclusion criteria were final diagnosis of vitamin D deficiency defined by serum measurements and/or confirmed rickets defined by long bone x-rays. Exclusion criteria included malabsorptive disorders, renal tubular disorders, hereditary vitamin D dependent rickets and hereditary hypophosphatemic rickets. All the patients responded to vitamin D therapy. Data obtained from the medical records include date of birth, age, month of presentation, weight and length on presentation, region of origin, place of birth, length of time in Australia, gestational weight, birth weight, diet, and sun exposure.

One-hundred-twenty-six cases were included in the analysis. Of note, there was a doubling in the number of cases from 2002 to 2003. Males accounted for 64% of the cases and presented at a significantly younger age (10.8 vs. 22.5 months for females). The median age of presentation was 15 months, 66% presented under 2 years of age, and 25% presented at less than 6 months of age. The presenting features included hypocalcemic seizures (33%), bowed legs (22%), and sibling diagnosis (18%). In the hypocalcemic seizure group 50% presented at less than 6 months of age and 85% at less than 1 year of age. Males presented with hypocalcemic seizures 43.8% of the time. In the hypocalcemic group the levels of 25 hydroxy vitamin D were lower as compared to those without hypocalcemia. The overall cohort was smaller than the general population and there was a higher percentage of small for gestational age (SGA) babies compared to the expected rate. Siblings diagnosed and white Australians were less severely affected than others; the white Australian group presented more subacutely with bowed legs and incidental fractures and failure to thrive. This group also had a lesser degree of secondary hyperparathyroidism.

The most prominent regions of origin were people from the Indian subcontinent (37%), Africa (33%), the Middle East (11%). There were only 5 white Australian children (4%). There was seasonal variation with 68 presenting in the winter or spring, and hypocalcemic seizures were more common in the winter and spring. No or minimal sunlight exposure was reported in 89% of cases. Levels of 25 hydroxy vitamin D were low in 73% and significantly lower in the children who presented at less than 6 months of age, as compared to other age groups. Hypocalcemia was present in 52%, and PTH was raised in 80%. All 63 mothers tested were vitamin D deficient. There was x-ray evidence of rickets in 78%.

The authors stated that this is the largest case series of vitamin D deficient rickets, reported to date, from a developed country. The cohort presented is almost exclusively recent immigrants or first generation off-spring of an immigrant parent with maternal vitamin D deficiency and exclusive or prolonged breast feeding. Immigration trends over the last decade in Australia have shown a major increase from North Africa, the Middle East and Asian countries. The prevalence of rickets and vitamin D deficiency in adult women in these regions has been well reported; however vitamin D levels are not performed as part of a screening test for immigrants arriving in Australia. The authors concluded reduced sunlight exposure and poor vitamin D intake from dietary sources as part of the etiology for the rickets. The reason for male predominance is unclear. The researchers further state that the data do not fully reflect the characteristics or prevalence of rickets in Sydney, Australia because of incomplete ascertainment. They noted that the American Academy of Pediatrics (AAP) has released guidelines for vitamin D intake recommending that all infants have a minimum intake of 200 IU daily beginning in the first 2 months of life. Similar recommendations do not currently exist in Australia. Healthcare practitioners in Australia need to be re-educated about rickets and become aware of the groups at risk.

Robinson P, Högler W, Craig M, et al. The re-emerging burden of rickets: a decade of experience from Sydney. Arch Dis Child. 2006;91:564–568.

Editor’s Comment

This interesting report from Australia underscores the importance of country-of-origin to the emerging problem of hypocalcemic nutritional rickets now seen in pediatric practices. Indeed rickets has become more common in the United States and with changing immigration patterns is becoming a significant new problem in other countries, as well. Although the current report suffers from being retrospective and from some ascertainment bias, the results are nevertheless of significance. The recommendations of the AAP for vitamin D supplementation need to be heeded by practitioners in other parts of the world. It is likely that nutritional rickets is not limited to those areas where prevalent studies are currently being described.

William L. Clarke, MD

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Last Updated: 04/30/2008