Acne keloidalis nuchae is also a scarring alopecia. It is seen most commonly in African American men and presents as keloid-like papules and plaques with occasional pustules characteristically on the occipital scalp and posterior neck. In contrast to FD, acne keloidalis nuchae papules coalesce and may form firm, hairless, protuberant keloid-like plaques that may be painful and cosmetically disfiguring. The cause of acne keloidalis nuchae is unknown.
Shaving or cutting tight curly hair too short and subsequently having the new hair curve back and penetrate the skin may be the precipitating event. Thus, a history of close shaving should make one suspect this diagnosis. Histologic analysis reveals a chronic, predominantly lymphocytic folliculitis with eventual follicular destruction.
Erosive pustular dermatosis is a rare disorder that primarily aff ects the elderly. It is characterized by a chronic amicrobial pustular dermatosis with extensive boggy, crusted, erosive plaques on the scalp resulting in scarring alopecia. Most cases have an onset after the age of 40. Therefore, age of onset may help diff erentiate between erosive pustular dermatosis and FD.
The cause of erosive pustular dermatosis is unknown. It is thought to be related to local trauma, such as chronic sun exposure, occurring months to years prior to the onset of lesions or as an autoimmune process.6 Histologic specimens show nonspecific changes including parakeratosis or hyperkeratotic scale with atrophy or erosion of the epidermis, while an inflammatory infiltrate with lymphocytes and plasma cells is found in the dermis.