Varying role of vitamin D deficiency in the etiology of rickets in young children vs. adolescents in northern India

The relative importance of calcium vs. vitamin D deficiency in the etiology of nutritional rickets in the tropics may be different in children compared with adolescents. We studied calcium intake, sun exposure, serum alkaline phosphatase, and 25 hydroxyvitamin D in 24 children and 16 adolescents with rickets/osteomalacia. The values were compared with those obtained in control subjects (34 children and 19 adolescents). We found that young children with rickets had lower calcium intake compared with controls (285+/-113 vs. 404+/-149 mg/day, p<0.01), but similar sun exposure (55+/-28 vs. 56+/-23 min.m(2)/day) and 25 hydroxyvitamin D (49+/-38 vs. 61+/-36 nmol/l). Sixteen of 24 children with rickets had 25 hydroxyvitamin D above the rachitic range (>25 nmol/l), in contrast to one of 16 adolescents. Adolescent patients had low calcium intake vs. controls (305+/-196 vs. 762+/-183 mg, p<0.001), and lower sunshine exposure (16+/-15 vs. 27+/-17 min.m(2)/day, p<0.01) and serum 25 hydroxyvitamin D (12.6+/-7.1 vs. 46+/-45.4 nmol/l, p<0.001). The odds ratio for developing rickets with a daily calcium intake below 300 mg was 4.8 (95 per cent CI, 1.9-12.4, p=0.001). Subjects with rickets were randomized to receive 1 g calcium daily, with or without vitamin D. Children showed complete healing in 3 months, whether they received calcium alone or with vitamin D. Adolescents showed no response to calcium alone, but had complete healing with calcium and vitamin D in 3-9 months (mean 5.3 months). Thus deficient calcium intake is universal among children and adolescents with rickets/osteomalacia. Inadequate sun exposure and vitamin D deficiency are important in the etiology of adolescent osteomalacia.