Actinic Superficial Folliculitis after Sun Exposure in a 29-Year-Old Woman

Abstract

The authors report the clinical case of a 29-year-old Caucasian woman who presented with clinicopathological findings and a previous outbreak all suggestive of actinic superficial folliculitis, a rarely reported and probably misdiagnosed phototoxic sun-induced dermatosis first described by Nieboer in 1985. Despite the exuberance of this cutaneous eruption, it is usually auto-limited, reinforcing the importance of its knowledge, for eviction of unnecessary diagnostic tests and therapies. Mechanisms of pathogenesis postulated include ultraviolet A radiation and local heat. This photodermatosis presents as monomorphic, superficial, pustular, and non-pruritic folliculitis affecting the upper body but not the face, usually arising on neck, back, shoulders and upper trunk. The follicular pustules emerge 24 -72 h after intense exposure to heat and/or sunlight and fade spontaneously in 5 -10 days, without scarring. This patient showed a 48-hour latency period; the number of pustules and area of the body affected were proportional to the duration of the sunlight exposure; the eruption lasted approximately 10 days. Actinic superficial folliculitis has a specific histology with follicular subcorneal sterile pustules and a mixed inflammatory infiltrate around hair follicles, probably secondary to keratinocytes and Langerhans cells involvement in the immunomodulatory actions of ultraviolet radiation. Recurrence under identical conditions may occur, after a latency period of at least 4 weeks, but usually about 1 year. Actinic superficial folliculitis and related follicular conditions are probably underdiagnosed and subsequently there is insufficient scientific information available to clinicians. Being familiar with these entities is of the utmost importance, since it can be crucial for their management.