Association between bullous pemphigoid and hypovitaminosis D in older inpatients: Results from a case–control study

• Bullous pemphigoid is an autoimmune subepidermal blistering disease affecting older adults.
• Hypovitaminosis D is associated with a greater incidence of autoimmune diseases.
• The association between hypovitaminosis D and BP is still open to debate.
• BP was significantly associated with hypovitaminosis D in older inpatients.

ObjectivesTo compare serum vitamin D status in older inpatients with bullous pemphigoid (BP) and matched inpatients without BP, and to examine whether hypovitaminosis D, a high comorbidity burden or their combination were associated with BP.MethodsThis prospective case–control study was performed from November 2012 to February 2014. A total of 90 consecutive older inpatients (31 consecutive inpatients with a de novo diagnosis of active BP, and 59 matched controls without BP) were recruited in the Department of Dermatology of Angers University Hospital, France. Hypovitaminosis D was defined as serum 25-hydroxyvitamin D (25OHD) concentration < 50 nmol/L. Age, gender, functional level, sun exposure, season, comorbidity burden and cognitive performance were used as covariates.ResultsThere was no significant difference between older inpatients with and without BP. Fully adjusted logistic regression showed a significant association between BP and hypovitaminosis D (odds ratio [OR] = 3.7, P = 0.046). The analysis of interaction between hypovitaminosis D and comorbidity burden showed that only the association of both was significantly associated with PB (OR = 3.1, P = 0.042).ConclusionsBP was significantly associated with hypovitaminosis D solely in patients with a high comorbidity burden among the older in-patients studied. This result suggests a complex interplay between hypovitaminosis D and BP, explaining the mixed results reported previously in the literature.