To the untrained eye the main impression of an acute lesion is the inflammatory, focal process. The most frequent mistake is therefore a failure to recognize what appears as a "common" abscess as a manifestation of HS. Carbuncles, furunculosis, lymphadenitis, infected Bartholin's gland, and the infected epidermal cyst are therefore to be differentiated from early lesions .
Carbuncles and furunculosis and other staphylococcal skin infections are often asymmetrical in distribution and by their nature they involve random areas of the skin. Upon examination pathogens are commonly found. Treatment is generally rapidly rewarding when topical and systemic antibiotics are used simultaneously. In addition to identifying the offending pathogens in the lesions, carriers or other sources of infection can often be properly identified and treated. Paraclinically, these patients also show signs of infection, such as elevated erythrocyte sedimentation rates, granulocyto-sis, etc.
When inflammation is not caused by microorganisms alone, the situation is much more similar to HS, and extra care has to be taken in establishing the correct diagnosis. Epidermoid (or epithelial) cysts, mistakenly called sebaceous cysts, can be present in HS patients; they may exist independently from HS and when in an axillary or inter-mammary localization with occasional inflammation are frequently considered erroneously as HS. The cysts are however most often single and therefore lack the basic symmetry of HS. Furthermore, a primary element may be recognized. The true epidermoid cyst is a superficial firm elastic dome-shaped nodule mobile over the deeper structures. Clinically there may be a central punctum but even in the absence of this, there is often a history of occasional expression of the semi-solid keratinous, foul-smelling and greasy content. Ultrasound examination often reveals a canal corresponding to the central punctum. The identification of the epidermal sack is of course also possible after incision.
True sebaceous cysts form a smooth elastic swelling; they have an oily content. They may be solitary or be part of a steatocystoma multiplex
(also called sebocystomatosis). Steatocystoma multiplex may be differentiated from HS by the finding of innumerable cysts evenly distributed over the entire skin, and not only limited to inverse areas. Its association with HS is not well documented.
Late lesions in the ano-perineal location are to be distinguished from other chronic scarring inflammations such as tuberculosis, actinomycosis, cat-scratch disease and lymphogranuloma venereum. For this region an important and difficult differential diagnosis is anal Crohn's disease (see Chap. 7).
In general, the differential diagnoses must be considered, but rarely form true diagnostic dilemmas for the experienced clinician. The coexistence of a number of other diseases which naturally occur when a disease is as common as HS may, on the other hand, present as significant confounders in the diagnostic process, and subsequent nosology of the disease. The co-existing diseases are discussed in greater detail in Chap. 6.
Was this article helpful?