The importance of histopathologic aspects in the diagnosis of dissecting cellulitis of the scalp.

Dissecting cellulitis of the scalp or dissecting folliculitis also known as "perifoliculitis capitis abscedens et suffodiens" (PCAS), is a rare, severe and distinct dermatological disease. It most probably occurs because of follicular occlusion via hyperkeratosis, having the same mechanism of acnea conglobata and hidradenitis suppurativa. These dermatoses may be associated or may have an isolated evolution. PCAS is one of the primitive cicatricial alopecia of neutrophilic type (with pustules). What is characteristic for the histopathologic picture of the disease is the deep inflammatory infiltrate, placed at the reticular derm or hypoderm level. The initial perifolliculitis evolves towards forming profound abscesses and the destruction of polysebaceous follicles because of granuloma, usually lymphoplasmocitary and with gigantic cells. Here is the case of a 24-year-old male with records of acne conglobata and cicatricial alopecia of the scalp, with relapsed inflammatory nodular lesions on the surface of the alopecic plaques and follicular pustules on their margin. The patient had followed before hospitalizing a systemic treatment with antibiotics (azithromycin, tetracycline, ciprofloxacin, in therapeutic schemes that the patient cannot mention, but anyway of short time) and after that a treatment with retinoids (isotretinoin, 20-30 mg/day, in two successive therapies of one month each). The evolution of the disease under these treatments was with outbreaks and short times of remission of the acne lesions and nodular lesions of the scalp. The clinical diagnosis of PCAS is difficult, especially in the initial stage of the disease, as it was the case of the patient presented here. We underline the importance of a correct history of the disease, of the complete clinical exams and the need of paraclinical investigations (histopathologic exam from the lesional biopsy - microscopy and immunohistochemistry) in order to come with a positive diagnosis of PCAS and a differential one.