ApaI polymorphism of vitamin D receptor affects health-related quality of life in patients with primary sclerosing cholangitis

BACKGROUND Polymorphisms of vitamin D receptor (VDR) contribute to the pathogenesis of multiple autoimmune conditions. METHODS We investigated the incidence of VDR polymorphisms (rs1544410-BsmI; rs7975232-ApaI; rs731236-TaqI) in a group of patients with primary sclerosing cholangitis (PSC, n = 275) and in healthy controls (n = 376). Additionally, correlations of the VDR polymorphisms with clinical and biochemical factors of the disease were analysed. RESULTS The genotype and allele distributions of these polymorphisms in PSC patients were similar to those observed in controls. However, the ApaI polymorphism was associated with an impaired health-related quality of life (HRQoL). The generic SF-36 questionnaire showed that the Role-Physical (p = 0.01), Role-Emotional (p = 0.01), Physical Component Summary (p = 0.01) and Mental Component Summary (p = 0.003) scores were significantly affected. Similarly, the disease-specific questionnaires, PBC-40 and PBC-27, demonstrated that carriers of the C allele suffered from more severe Itch (p = 0.03 assessed by PBC-40 and PBC-27), more Fatigue (p = 0.02 assessed by PBC-40 and PBC-27) and Impaired Cognitive Capacity (p = 0.04 and p = 0.03). Correspondingly, individuals who were AA homozygotes (non-carriers of the C allele of ApaI) had higher summary scores for the Physical (p = 0.01) and Mental Components (p = 0.006) measured with SF-36. Moreover, they experienced less itch (p = 0.03) and less Fatigue (p = 0.03) and had better Cognitive Abilities (p = 0.04) as assessed by the PBC-40 and PBC-27 questionnaires. No associations between other VDR polymorphisms and clinical or laboratory findings were made. CONCLUSION In summary, this study is the first to show that the ApaI polymorphisms in VDR may exert an effect on disease-related symptoms and quality of life in patients with PSC.