Cutaneous comorbidity in patients with seborrhoeic dermatitis

Seborroheic dermatitis is one of the commonest dermatological disorders affecting up to 5 % of the population worldwide, yet its pathogenesis is still unknown. Although this disorder has high prevalence and affects socially important parts of the skin like face and scalp large studies on its epidemiology and comorbidity are not conducted. The purpose of our study was to evaluate the prevalence of comorbid skin conditions in seborhhoeic dermatitis patients. 225 patients with clinically manifested seborrhoeic dermatitis were examined clinically for presence of other cutaneous disorders. The data was compared with a control group of 120 healthy subjects and 1215 consecutive dermatological outpatients. 62% of patients with seborrheic dermatitis showed skin comorbidites. Most common associated with seborrheic dermatitis conditions were acne, extragenital warts, onychomycoses and contact dermatitis. Compared with control groups most significant was the difference in prevalence of HPV infection manifestations. This result suggests common pathological mechanisms in both conditions. Interestingly our study did not show Malassezia-caused conditions to be more frequently found in patients with seborrheic dermatitis. The comorbidity with psoriasis, dyshidrosis, rosacea and mycotic infections of the skin was comparable with that found in the control groups. Furthermore patients with seborrhoeic dermatitis showed higher prevalence of alopecia areata and small plaque parapsoriasis, but largers studies are needed to confirm the significance of these results.