What’s new in acne inversa (alias hidradenitis suppurativa)?

Acne inversa (alias acne triad, acne tetrad, pyodermia fistulans sinifica, and hidradenitis suppurativa) is a chronic, suppurative, and cicatricial disorder that affects skin areas rich in apocrine glands, such as the axillae, groin, and perineum.1,2 The diagnosis is primarily clinical, based on the presence of both sinus tracts and abscesses with a characteristic distribution. These lesions usually respond poorly to antibiotics and tend to recur. Eventually chronic abscess formation with progressive scarring may become constant. Recurrent, foul-smelling discharge from draining sinuses may cause extensive soiling of clothes, forcing the individual to limit social contact and forfeit employment. Attendant physical discomfort may preclude sexual contacts or even walking. Malignant degeneration in chronic sinus tracts is a rare long-term result. Squamous cell carcinomas that arise in chronic scarred and inflamed skin tend to be more aggressive than those resulting from chronic actinic damage and are associated with local invasion or recurrence after excision, distant metastasis, and high mortality.3 Articular manifestations occur sporadically in patients with acne inversa. The findings are similar to those seen in other seronegative spondyloarthropathies, except for lack of association with HLA-B27. It has been speculated that acne inversa appears to be another cutaneous manifestation of Crohn’s disease.4 However, this remains to be verified. Perianal lesions are the initial presentation in 5% of all patients with Crohn’s disease and, at times, these two diseases may be clinically indistinguishable. The comorbidity of acne inversa and Crohn’s disease has been reported, the latter typically preceding the development of acne inversa. The classic view of acne inversa is that it is an occlusive and pyogenic disorder of the apocrine glands, an hypothesis that seemed confirmed with its experimental reproduction by Shelley and Cahn5 in 1955. However, apocrine gland involvement is incidental but not essential to the pathogenesis. Inflammation of apocrine glands is a secondary phenomenon. More recent studies have shown that acne inversa is actually a defect of terminal follicular epithelium.6 The earliest change seen in acne inversa is plugging of follicular hyperkeratosis. The association of acne inversa with several disorders in which poral occlusion is prominent, such as Fox–Fordyce disease, pityriasis rubra pilaris, acanthosis nigricans, steatocystoma multiplex, and Dowling–Degos disease,7 adds support to the follicular theory of origin of acne inversa. Thus the term hidradenitis suppurativa is a misnomer and should be abandoned. The inciting influences for the follicular occlusion have not been fully elucidated but may result from a folliculitis induced by local frictional trauma. Chemical irritants such as deodorants, mechanical irritation, depilation, and shaving have been considered as aetiological factors. However, no significant difference in the use of these items compared with age-matched controls was found. Obesity may not be an aetiological factor, although the increased skin-to-skin contact may promote follicular hyperkeratosis. An individual predisposition to follicular occlusion and sinus tract formation is probably important. Genetic factors may play a role, as a familial form of the disease has been described.8 Several reports in the literature link acne inversa to a single gene transmission. The pattern of transmission and the number of affected individuals are consistent with autosomal dominant inheritance. HLA associations are not consistent. Androgenic influences may contribute to the predisposition, although hormonal abnormalities are usually not demonstrable in these patients.9 The absence of acne inversa in children and its onset postpubertally suggest the importance of hormonal factors in its pathogenesis. Cigarette smoking has been suggested as an aetiological factor in the development of the disease, but as yet, this has not be confirmed. Most patients with acne inversa are otherwise healthy, and no predictable association with systemic diseases such as diabetes mellitus is to be anticipated. Immune defence mechanisms are normal in affected patients. Bacterial involvement of acne inversa is not a primary pathogenic event, but is secondary to the disease process. The microbiological flora is not constant and may change unpredictably. Various bacteria can be isolated from the lesions, particularly staphylococci, streptococci, and gram-negative rods.10 Several authors have implicated Streptococcus milleri and Chlamydia trachomatis as major pathogens in acne inversa, but this could not be confirmed by others. It is likely that bacteria may contribute to the inflammatory process. Acne inversa is curable, despite the pessimism of many who have been frustrated in their efforts to obliterate the disease. Although surgery can often be avoided in early stages of acne inversa, it is an essential part of the treatment of advanced forms and should be performed as early as possible.11 Wide excision, well beyond the clinical borders of activity, is mandatory, regardless of the localization of the disease. Best functional results appear to be obtained with healing by granulation (secondary intention). With rare exceptions, surgical intervention is sufficient to stop the disease. Improper surgery is doomed to fail and delays definitive treatment, although exceptional cases resolve spontaneously. Patients should be cautioned that new lesions may develop at a site not affected at the time of their initial surgery. In some cases, carbon dioxide laser treatment may provide an alternative efficient method for the management of acne inversa. The advantage of laser treatment has been considered to be improved haemostasis, which affords better visualization and therefore more complete removal of the affected tissue. Systemic isotretinoin (13-cis-retinoic acid) is not as beneficial in acne inversa as it has been shown to be in acne vulgaris. In general, drugs such as retinoids, corticosteroids, antibiotics, and antiandrogens are not curative, and relapse is almost inevitable when such treatment is withdrawn. However, these drugs may be useful as an adjunctive treatment to reduce the inflammation before and after surgery.