ANSWER
The correct answer is seborrheic dermatitis (choice “d”), a common cause of penile rashes that typically manifests initially as chronic dandruff or in some other form on the head or neck.
Herpes simplex (choice “a”) is certainly common, but it likely would have presented with grouped vesicles on an erythematous base. Furthermore, each episode would have been limited to about two weeks, and the eruption would have produced noticeable symptoms and responded to the valacyclovir.
Yeast infection (choice “b”), while often diagnosed, is in reality unusual, especially in the circumcised and otherwise healthy male. Nystatin, although far from the ideal treatment, should have had some effect.
Fixed drug eruption (FDE; choice “c”) could have been a suspect, had there been a drug to blame. FDE usually presents as a brownish red, shiny round macule that appears and reappears in the same area with repeated exposure to the same drug. The penile shaft is a favorite area for it. Drugs known to trigger FDE include NSAIDs, sulfa, tetracycline, penicillin, pseudoephedrine, and aspirin.
DISCUSSION
Seborrheic dermatitis (SD), also known as seborrhea, is an extremely common chronic papulosquamous disorder patterned on the sebum-rich areas of the scalp, face, and trunk. Although not directly caused by the highly lipophilic commensal yeast Malassezia furfur, it does appear to be related to increases in the number of those organisms, as well as to immunologic abnormalities and increased production of sebum. It can range from a mild scaly rash to whole-body erythroderma and can affect an astonishing range of areas, including the genitals.
SD almost always manifests with dandruff (or “cradle cap” in the infant), followed by faint scaling in and around the ears or on the face (eg, nasolabial folds, brows, and glabella), mid chest, axillae, periumbilical region, and genitals. Below the head and neck, SD often mystifies the nondermatology provider, who tends to call it “fungal infection” or, when it’s seen in moist intertriginous skin, “yeast infection.”
SD, especially in this case, represents the perfect example of the need to “look elsewhere” for clues when confronted with a mysterious rash. Patients can certainly have more than one dermatologic diagnosis at a time, but a single explanation is considerably more likely and should therefore be sought. In this case, corroboration for the diagnosis of SD was readily found by looking for it in its known locations.
SD can take on different looks, including a distinctly annular morphology, especially in patients with darker skin. It can occasionally be severe in patients with Parkinson’s disease, multiple sclerosis, or a history of stroke. This case mirrors my experience in that I see increased stress as a major precipitating factor in the worsening of pre-existing SD.
In addition to the items already mentioned, the differential for penile rashes includes lichen planus. However, the lesions of lichen planus tend to have a distinctly purple appearance and well-defined margins, and on the penis, they tend to spill over onto the penile corona and glans.
TREATMENT/PROGNOSIS
In this case, treatment comprised a combination of oxiconazole lotion and 2.5% hydrocortisone cream. Many other combinations have been used successfully, including pimecrolimus or tacrolimus combined with ketoconazole cream.
Whatever is used, a cure will not be forthcoming, since the condition is almost always chronic. The main value of an accurate diagnosis in such a case lies in easing the patient’s mind regarding the terrible diseases he doesn’t have.