Associations among behavior-related susceptibility factors in porphyria cutanea tarda.

Porphyria cutanea tarda (PCT) is the most common of the human porphyrias and results from an acquired deficiency of hepatic uroporphyrinogen decarboxylase (UROD). Some susceptibility factors have been identified; we examined associations among multiple factors in a large cohort of patients. Multiple known or suspected susceptibility factors and demographic and clinical features of 143 patients (mean age 52 years, 66% male, 88% Caucasian) with documented PCT (mean onset at 41 +/- 8.8 years) were tabulated; associations were examined by contingency tables, classification and regression tree (CART) analysis, and logistic regression. The most common susceptibility factors for PCT were ethanol use (87%), smoking (81%), chronic hepatitis C virus (HCV) infection (69%), and HFE mutations (53%; 6% C282Y/C282Y and 8% C282Y/H63D). Of those who underwent hepatic biopsy or ultrasound, 56% had evidence of hepatic steatosis. Of those with PCT, 66% of females took estrogen, 8% were diabetic, 13% had human immunodeficiency virus (HIV) infection, and 17% had inherited uroporphyrinogen decarboxylase (UROD) deficiency (determined by low erythrocyte UROD activity). Three or more susceptibility factors were identified in 70% of patients. HCV infection in patients with PCT was significantly associated with other behavior-related factors such as ethanol use (odds ratio [OR], 6.3) and smoking (OR, 11.9). Susceptibility factors for PCT were similar to previous studies; most patients had 3 or more susceptibility factors. Associations between PCT and HCV, ethanol or smoking could be accounted for by a history of multiple substance abuse; other factors are distributed more randomly among patients.