Nutritional rickets in children with cows’ milk allergy: calcium deficiency or vitamin D deficiency?

Editor, We read with interest the paper published by Fox et al. (1). The paper describes a 14-monthold boy with AEDS and cows’ milk allergy who developed nutritional rickets. The authors emphasize the role of vitamin D deficiency in this case [exclusive breast feeding without soy-based formula supplementation, limited solid foods, and other risk factors such as pigmented skin, low birth weight, lack of supplemental vitamin D, and inadequate sunlight (1)]. It is worthwhile to remember that nutritional rickets might develop in cows’ milk allergic children due to calcium deficiency as we described in our paper in 1993 (2). Our patient was a 4-yr-old boy with atopic dermatitis and cows’ milk allergy diagnosed at the age of 3 months. Breast feeding was stopped at the age of 1 yr. He did not receive soy-based formula or hypoallergenic formula and his diet included meat, potatoes and cabbage. Nutritional assessment at the age of 4 yr revealed that the child was receiving 180 mg calcium daily (the recommended daily allowance is 800 mg). The biochemical parameters in the blood tests were compatible with calcium deficiency rickets: low serum calcium and phosphate levels, high serum alkaline phosphatase and parathyroid hormone levels, normal serum 25-hydroxyvitamin D and high serum 1,25dihydroxyvitamin D levels. The patient improved rapidly with oral calcium carbonate supplementation and a maintenance dose of vitamin D2 (200 U/day). At the time our paper was published, calcium deficiency rickets had been described in children with special diets, such as South African children whose diet did not contain milk or milk products (3). Recent literature search reveals that nutritional rickets resulting from calcium deficiency may pertain nowadays also in children in North America (4) as well as in children in sunny countries such as Nigeria and South Africa (5). Low dietary calcium intake after weaning may result in the development of nutritional rickets. Cows’ milk allergic infants and children should be carefully assessed for their calcium intake. If the consumption of soy-based formula or hypoallergenic formula (all enriched with calcium) is low or stopped, dietician consultation is required and calcium supplementation should be considered.