Body mass index in psoriatic patients with or without familial psoriasis

Psoriasis is a chronic inflammatory disease caused by both genetic and environmental factors. The occurrence of psoriasis in family members indicates a genetic predisposition, while obesity is also a major contributor to psoriasis. We examined whether patients with versus without familial psoriasis were obese at the onset of psoriasis. Clinical information, including age at onset, age at first visit and body mass index (BMI) at first visit, was extracted from the Fukuoka University Psoriasis Registry. To compare BMI, patients aged 10 years or older who visited the clinic within 3 years of onset were selected. Familial psoriasis was observed in 27 patients (15 male, 12 female) out of 428 individuals (264 male, 164 female) with psoriasis, accounting for 6.3% of cases. Age at onset was younger for both men and women with familial psoriasis (34 ± 17 and 40 ± 15 years, respectively) relative to those with non-familial psoriasis (48 ± 19 and 53 ± 19 years, respectively). We examined age- and sex-adjusted average values of BMI at initial presentation after onset of psoriasis, finding that patients with familial psoriasis had lower BMI (22.0 kg/m² [95% confidence interval, 21.8-22.4]) than those with non-familial psoriasis (23.2 [23.1-23.3], P < 0.001). Individuals with a family history of psoriasis should be considered to be at risk for developing the disease even if obesity is not present.