Scarcity of published studies on osteopetrosis reduce the ability to develop evidence-based guidelines for the management of these patients. Expert opinion-based guidelines for this rare condition are nevertheless important to enable improved care.

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Rationale: Recent literature suggests vitamin D has an effect on lung function and on the lung's ability to fight infection, both important in the cystic fibrosis (CF) population as predictors of morbidity and mortality.Objectives: Our study assessed associations between vitamin D and % predicted lung function, pulmonary exacerbations, and first Pseudomonas aeruginosa infection in children with CF. We hypothesized that children with CF who have 25-hydroxy vitamin D (25-OHD) levels less than 30 mg/L would have lower % predicted lung function and more pulmonary exacerbations than those with 25-OHD greater than or equal to 30 mg/L. Measurements and Main Results:The prevalence of vitamin D deficiency and insufficiency increased slowly through adolescence. The rate of exacerbations for the deficient vitamin D group, aged 15 to 18 years, was 13.1 per 10 patient-years, significantly higher than 4.3 per 10 patient-years for the insufficient and sufficient vitamin D groups (P , 0.05), which were not significantly different There were no differences between vitamin D groups in pulmonary function or incidence of first P. aeruginosa infection, which was about 2 per 10 patient-years.Conclusions: Higher 25-OHD levels in children with CF were associated with lower rates of pulmonary exacerbations and, in adolescents, higher FEV 1 .