How do you explain this persistent itchy eruption?

Case 2:
For a few months, a 27-year-old man has had an itchy rash in the groin area. He tried an over-the-counter “jock itch” remedy, but it was not effective. He is otherwise healthy.
Which of the following would you include in the differential diagnosis?

A. Tinea cruris.
B. Candidiasis.
C. Erythrasma.
D. Intertrigo.
E. Seborrhea.
F. Psoriasis.

Case 2: Sebopsoriasis

This patient has sebopsoriasis, which is defined as psoriasis, F, in a seborrheic distribution, E. Seborrheic dermatitis occurs on the sebum-rich areas of the scalp, face, and trunk. This papulosquamous disorder is also associated with Malassezia species, immunological abnormalities, and activation of the alternative complement pathway. It is commonly aggravated by changes in humidity and in seasons, trauma (eg, scratching), and emotional stress.

A skin biopsy may be needed to rule out the other conditions in the differential. However, the dermatopathological findings of seborrheic dermatitis are nonspecific; they include hyperkeratosis, acanthosis, accentuated rete ridges, focal spongiosis, and parakeratosis. Psoriasis is distinguished by regular acanthosis, thinned rete ridges, exocytosis, parakeratosis, and an absence of spongiosis. Neutrophils may be seen in both diseases.

Topical corticosteroids may hasten recurrences of sebopsoriasis and may foster dependence because of a rebound effect; thus, these agents should be reserved for short-term use only. Class IV or lower corticosteroid creams, lotions, or solutions can be used for acute flares.

The dermatitis usually responds to ketoconazole, naftifine, or ciclopirox creams and gels. Alternatives include calcineurin inhibitors (ie, pimecrolimus, tacrolimus), sulfur or sulfonamide combinations, or propylene glycol. Systemic ketoconazole or fluconazole may help if the condition is severe or unresponsive.