The correct answer is hidradenitis suppurativa (HS; choice “c”).
HS (also known as acne inversa) is a relatively common condition first described in 1839 by French physician Frederick Velpeau, who thought it was probably a form of acne. Because HS only affects intertriginous areas (groin, axillae, inframammary, intergluteal, and abdominal folds rich in apocrine glands), during the next 130 years, it was presumed that this disease was solely caused by malfunctioning apocrine glands.
Though experts disagree about the true etiology of HS, most agree that it is caused by several environmental and genetic factors leading to plugged or malfunctioning hair follicles and apocrine glands that become inflamed, swollen, painful, and purulent. In severe cases, tracts develop between lesions, resulting in the formation of ropy, linear hypertrophic scarring. Early on and in milder cases, comedones can manifest—often in multiples—along with widely scattered cysts. It appears that a case can be made for a genetic predisposition to develop HS because at least one-third of affected patients report a positive family history.
Females (usually postpubescent) are affected at 3 times the rate of males. Hormones, especially androgens, appear to play a role. This assertion is bolstered not only by the age of onset, but also because HS has been observed to improve after pregnancy and after menopause.
Though not causative, smoking and obesity have a strong statistical correlation with HS as exacerbating factors. Many patients with HS find movement from exercise too painful, which may contribute to obesity.
Because HS has a wide range of clinical presentations, the Hurley Staging scale can help clinicians distinguish the condition’s severity by stages I, II, or III. Stage I manifests with scant signs of disease, including comedones and sparsely separated small cysts. Stage II includes numerous painful cysts with tract formation between lesions. Stage III involves symptoms described in the other stages as well as multiple large, painful, draining cysts; widespread erythema; and extensive hypertrophic scarring.
Regarding the differential, the culture would have identified community-acquired methicillin-resistant Staphylococcus aureus (choice “a”) or flesh-eating bacterial infection (choice “d”), but neither would be as chronic as the patient’s disease. Acne conglobata (choice “b”) manifests with chronic dense acne largely confined to the trunk. Interestingly, acne conglobata, HS, dissecting cellulitis of the scalp, and pilonidal cyst are collectively known as the follicular occlusion tetrad.
Treatment for HS is limited. Adalimumab is the most recent and promising biologic, though its use comes at a high cost ($60,000/y) and with an adverse effect profile that should give any prescriber pause. Also, the best one could hope for in using adalimumab is about a 30% improvement in the patient.
Before using a biologic, other options should at least be considered. Though not entirely satisfactory, there are oral antibiotics (minocycline, trimethoprim/sulfa, or a combination of rifampin and clindamycin) or intralesional steroids. Incision and drainage of individual lesions and isotretinoin therapy can temporarily relieve pain, but they are not effective as long-term therapies. Large-scale surgical extirpation of the affected tissue can be considered in extreme cases, but there can be recurrences and associated morbidity (eg, chronic lymphedema in the affected arm, extreme scarring, and postoperative pain).