Although<unk>  is often referred to as acne inversa, it is not a form of acne, and lacks the core defining features of acne such as the presence of closed comedones and increased sebum production.
Hidradenitis suppurativa
Acne
Folliculitis decalvans
Pilonidal disease
Streptococcal intertrigo
Acne conglobata
Helicobacter cellulitis
Keratolysis exfoliativa