A 64-year-old man self-refers to dermatology for evaluation of an asymptomatic rash that has been present on his groin for more than a year. He has tried a number of topical antifungal creams (terbinafine, tolnaftate, and miconazole) and oral antifungal medications (terbinafine and ketoconazole), none of which produced any beneficial effect.
The rash, which has been constant and limited to the groin, started around the same time his mother became ill. She eventually succumbed to cancer, leaving a number of stressful tasks for the patient to complete. As a result, the patient had to leave his job and spend a good deal of time away from home, repairing and then selling his mother’s home and possessions.
At his first visit to dermatology, the groin rash is bright orange-red, covers both crural areas, and exhibits sharply defined margins that are faintly scaly. However, a KOH prep fails to demonstrate fungal elements, and since a number of antifungal treatments have already been tried without success, a provisional diagnosis of erythrasma is made. The patient is given topical clindamycin solution and oral cephalexin (500 mg tid for a week).
Neither of these treatments changes the rash at all, so the man returns for a second visit. Since the rash is asymptomatic, you are not inclined to biopsy it. Clearly, the rash is neither fungal nor bacterial in origin, but in an effort to try something, you go to the supply room seeking samples of a mild steroid cream.
When you return to the exam room, you find the man’s wife closely examining his scalp. When you ask what she is looking at, she says she is checking his dandruff, which has been flaring for months. When you look, you see that he does indeed have a brisk case of dandruff. Checking elsewhere, you notice that his external auditory meati are scaly and red, as are the eyebrow, postauricular sulci, and perinasilar areas. There are focally scaly, salmon-pink sites in his beard.
The correct answer is seborrhea (choice “c”), aka seborrheic dermatitis, a papulosquamous condition known to affect a variety of areas, including the groin and axillae. This patient could have had a close cousin of seborrhea, psoriasis (choice “a”), but he was missing corroborative involvement of his elbows, knees, and nails.
Groin rashes are often misdiagnosed as “yeast infections” (choice “b”); however, candidal involvement of the groin is actually quite unusual in men, and it would almost certainly have responded well to the imidazoles the patient had tried.
Eczema (choice “d”) is certainly common enough, but it is almost invariably highly pruritic and seldom affects the groin exclusively. It is therefore an unlikely choice.
This case nicely illustrates several useful points. One is that the differential for groin rashes is extensive (18 items long!) and demands careful thought, since cancer (eg, cutaneous T-cell lymphoma and extramammary Paget’s disease) can present as a rashlike eruption in the groin. The lack of response to the “usual and customary” treatments is precisely what should prompt further consideration.
Another learning point to be gleaned from this case is: When stumped, look elsewhere. Can’t figure out the groin rash? Look elsewhere, anywhere, for clues, when puzzled. In this case, finding signs of seborrhea elsewhere raised that possibility in the groin as well. Corroboration was also provided by the history of antecedent stress, a well-known trigger for flares of seborrhea, and by the relative lack of symptoms.
Treatment in this case entailed hydrocortisone 2.5% cream, but the real “cure” will only come with serious reduction of the patient’s stress level. His topical steroid use will be limited to no more than five consecutive days, with a break for two consecutive days per week.
Our real contribution to this patient’s well-being is in establishing the correct diagnosis and “selling” it to the patient, optimizing his confidence in the benignancy and self-limiting nature of his problem.