Certain severe forms of acne vulgaris may be accompanied by disorders of the locomotor system. Fulminant acne is manifest as an acute disorder with an alteration of general health and with fever, the onset of painful, necrotic skin lesions, myalgia and arthralgia with arthritis of one or more joints. Acne conglobata, a chronic disorder, is defined by the presence of comedones in sebaceous gland ducts and its progression to form nodules and pustules, leaving indelible scars. Osteoarticular involvement which occurs during the course of acne conglobata, and whose incidence is difficult to determine, is characterized by the frequent presence of sacroiliac inflammation. However, these two forms of acne are often confused and the authors outline differences between them. A more accurate identification of cutaneous manifestations would perhaps provide an eventual classification of "rheumatic disturbances of acne" whose nosological category has not yet been determined.