Follicular occlusion tetrad

The follicular occlusion tetrad is a grouping of four chronic, relapsing inflammatory disorders of the hair follicle that share a common underlying process: follicular hyperkeratinization followed by blockage of the follicle, rupture, and secondary inflammation. The four conditions are hidradenitis suppurativa, which produces nodules, abscesses, and sinus tracts, acne conglobata, a severe nodulocystic form of acne with interconnected abscesses, dissecting cellulitis of the scalp, a suppurative scalp disorder that leaves scarring hair loss, and pilonidal disease, marked by recurrent sinus formation in the sacrococcygeal region at the base of the spine. These disorders typically arise in body regions rich in apocrine sweat glands and often occur together or in sequence in the same affected individual. Across all four, the shared clinical picture is recurrent abscess formation, sinus tract development, and eventual scarring in the affected apocrine bearing skin.