Vitamin D deficiency rickets in an adolescent with severe atopic dermatitis.

Atopic dermatitis (AD) affects 10% to 20% of children worldwide. Its severity may be inversely correlated with 25-hydroxyvitamin D (25OHD) levels. Although low levels of vitamin D (VD) can cause rickets in infants, VD deficiency rickets is an unusual presentation in teenagers. We report the case of a 14-year-old girl with severe AD and fish allergy since early childhood. She lived at high latitude (with less sun exposure) and, because of her atopic disorders, avoided sunlight and fish. Laboratory studies showed elevated alkaline phosphatase and parathyroid hormone levels and low serum calcium; her serum 25OHD level was <12 nmol/L. A radiograph of the wrist showed a radiolucent band in the distal metaphysis of the radius with marginal sclerosis. She was diagnosed as having hypocalcemic rickets due to VD deficiency. Treatment with VD increased her 25OHD level to 44 nmol/L, with normalization of alkaline phosphatase, parathyroid hormone, and calcium. Moreover, we observed a dramatic improvement in her AD severity with VD treatment. This case demonstrates the complex interaction between VD deficiency, AD, and food allergy. We advise a high index of suspicion of VD deficiency rickets in children of all ages with AD, particularly during accelerated growth periods and in the presence of other risk factors such as darker skin, living at high latitude, sun avoidance, and low intake of VD-rich foods. The concomitant improvement in bone-related parameters and AD severity may reflect a double benefit of VD treatment, a possibility that warrants research on VD as potential treatment for AD.