To determine temporal trends in incidence and risk factors of nutritional rickets in a community-based population.
Patients and Methods
Rochester Epidemiology Project (REP) data were used to identify all children (<18 years) residing in Olmsted County, Minnesota between January 1, 1970 and December 31, 2009 with diagnostic codes corresponding to rickets, vitamin D deficiency, hypovitaminosis D, rachitis, osteomalacia, genu varum, genu valgum, craniotabes, hypocalcemia, hypocalcemic seizure, and tetany. Record abstraction was performed to select subjects with radiographic confirmation of rickets. Age- and gender-matched controls were identified for evaluation of risk factors. The main outcome measure was radiographic rickets without identifiable inherited, genetic, or non-nutritional causes. Incidence rates were calculated using REP census data.
Of 768 children with eligible diagnostic codes, 23 had radiographic evidence of rickets; of these, 17 children had nutritional rickets. All were younger than 3 years and 13 (76%) were nonwhite. Clinical presentation included poor growth (n=12), leg deformity (n=8), motor delay (n=5), leg pain (n=3), weakness (n=3), and hypocalcemia or tetany (n=2). The incidence of nutritional rickets in children under 3 years was 0, 2.2, 3.7, and 24.1 per 100,000 for the decades beginning in 1970, 1980, 1990, and 2000, respectively (P=.003 for incidence trend). Nutritional rickets was associated with black race, breastfeeding, low birth weight, and stunted growth (P<.05 for all). Four of 13 (31%) who underwent 25-hydroxyvitamin D testing had values less than 10 ng/mL (25 nmol/L).
Nutritional rickets remains rare, but the incidence has dramatically increased after 2000. Not all cases can be attributed to vitamin D deficiency.