Vitamin D and skeletal health in autoimmune bullous skin diseases: a case control study

BACKGROUND The presence of hypovitaminosis D in patients with autoimmune bullous skin diseases, such as pemphigus vulgaris (PV) and bullous pemphigoid (BP), is debated. In a previous study we found an increased prevalence of vertebral fractures (VFx) and hypovitaminosis D in PV and BP patients. The present study extends the sample size of the previous one, for investigating the 25-hydroxyvitamin D (25OHVitD) levels in relation with the skeletal health and disease intensity in these patients. METHODS The previous study was performed in 13 PV and 15 BP patients and 28 controls. Data from 39 additional patients (22 PV and 17 BP) were now added. Eventually, we studied 67 patients (35 PV, 32 BP, 51 females), aged 64.7 ± 16.9 years and 67 age- gender- and body mass index-matched controls. In all subjects, serum 25OHVitD, calcium and alkaline phosphatase (ALP) levels were measured, bone mineral density (BMD) was evaluated by Dual-energy X-ray. Absorptiometry at lumbar spine (LS) and femoral neck (FN) and the presence of VFx were ascertained by visual assessment from spinal radiographs. In patients, the disease intensity was evaluated by the autoimmune bullous skin disorder intensity score (ABSIS). RESULTS As compared with controls, both PV and BP patients showed lower 25OHVitD (22.2 ± 11.1 vs 13.9 ± 8.3 ng/mL, p < 0.001 and 22.4 ± 14.9 vs 9.5 ± 7.7 ng/mL, p < 0.0001, respectively) and higher prevalence of severe hypovitaminosis D (22.9 vs 48.6%, p < 0.02 and 31.1 vs 75.0%, p < 0.0001, respectively) and VFx (28.6 vs 57.1%, p = 0.03 and 34.4 vs 62.5%, P = 0.02, respectively). In both PV and BP patients, LS and FN BMD did not differ from controls. In the whole patients' group, ABSIS score was inversely associated with 25OHVitD levels (R = -0.36, p < 0.005), regardless of age (β = -3.2, P = 0.009). CONCLUSIONS PV and BP patients have an increased prevalence of hypovitaminosis D and VFx. The extended study shows, for the first time, that the 25OHVitD levels are inversely associated with disease intensity and that VFx occur in spite of a not reduced BMD.