Nutritional rickets around the world: causes and future directions.

INTRODUCTION: Nutritional rickets has been described from at least 59 countries in the last 20 years. Its spectrum of causes differs in different regions of the world.
METHODS: We conducted a systematic review of articles on nutritional rickets from various geographical regions published in the last 20 years. We extracted information about the prevalence and causes of rickets.
RESULTS: Calcium deficiency is the major cause of rickets in Africa and some parts of tropical Asia, but is being recognised increasingly in other parts of the world. A resurgence of vitamin D deficiency has been observed in North America and Europe. Vitamin D-deficiency rickets usually presents in the 1st 18 months of life, whereas calcium deficiency typically presents after weaning and often after the 2nd year. Few studies of rickets in developing countries report values of 25(OH)D to permit distinguishing vitamin D from calcium deficiency.
CONCLUSIONS: Rickets exists along a spectrum ranging from isolated vitamin D deficiency to isolated calcium deficiency. Along the spectrum, it is likely that relative deficiencies of calcium and vitamin D interact with genetic and/or environmental factors to stimulate the development of rickets. Vitamin D supplementation alone might not prevent or treat rickets in populations with limited calcium intake.