Vitamin D deficiency and chronic pain in sickle cell disease.

Recent studies report a high prevalence of vitamin D deficiency (VDD) among patients with sickle cell disease (SCD), with rates as high as 65–100% depending on the season (Buison et al, 2004; Lal et al, 2006; Adewoye et al, 2008; Rovner et al, 2008; Chapelon et al, 2009). Despite this evidence, VDD remains both under-recognized and under-treated in patients with SCD. There appears to be substantial overlap between the symptoms of chronic pain seen in SCD and VDD. In both conditions, pain is commonly localized to the lower spine, pelvis and extremity bones and described as a dull, aching pain exacerbated by activity and weight bearing (Gloth & Greenough, 2004; Holick, 2007; Lofti et al, 2007; Straube et al, 2009). Both conditions are associated with an increased risk of low bone mineral density (BMD). Additional symptoms of VDD include muscle weakness, increased risk of falls and a predisposition to microor macro fractures (Holick, 2007). Though the relationship between vitamin D and chronic pain has yet to be fully understood, supplementation of vitamin D may serve a dual role in SCD patients by helping to improve both bone health and the chronic pain experience. Several studies have shown that the treatment of VDD led to improvement in pain symptoms and decreased the use of pain medications in non-sickle cell subjects with chronic pain (Gloth & Greenough, 2004; Straube et al, 2010). However, there has been no evidence to date implicating VDD to the adverse bone health outcomes seen in SCD. We therefore sought to determine the role, if any, of VDD in shaping the chronic pain experience of children and adolescents with SCD. Between January 2008 and January 2010, we evaluated 25-hydroxy vitamin D (25OHD) levels among 53 patients with SCD. All patients were in their steady state and were not experiencing an acute vaso-occlusive crisis (VOC) at the time of evaluation. Patients were selected because of frequent clinic visits due to the presence of either chronic pain, suspected or confirmed bone fragility, or other complications of SCD. In this study, chronic pain was defined as self-reported pain on