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40-Year-Old Male with Recurrent Erythematous Rash

Can you diagnose this case?

David L. Kaplan 2014 Series Editor @ University of Missouri – Kansas City School of Medicine

Signs and Symptoms

A 40-year-old East Indian man presented with a chronic, recurrent, erythematous rash limited to the inguinal and axillary areas for the past 3 years. The rash was pruritic and at times slightly macerated, but there was no scaling. He treated himself with some over-the-counter medications recommended by his pharmacist, but it was of minimal benefit. Medical history was significant for diabetes mellitus. He did not consume alcohol or smoke. His 65-year-old father had psoriasis.

On examination, there were well-demarcated, thin erythematous plaques in the inguinal and axillary regions. The skin surface was smooth, atrophic, non-scaly, and slightly shiny. He also had pitting of the fingernails. The rest of the physical examination was unremarkable.

What’s causing this man’s pruritic rash?

Choose one to reveal diagnosis and discussion

Extra-mammary Paget disease
Fungal intertrigo
Glucagonoma syndrome
Inverse psoriasis
Langerhans cell histiocytosis
Seborrheic dermatitis

Answer: Inverse psoriasis

See the full case at Consultant360

Diagnosis of inverse psoriasis is usually clinical, based on the characteristic features, and family history of psoriasis and typical psoriatic lesions in other areas may aid in the diagnosis. A mycologic examination of skin scraping using potassium hydroxide may at times be necessary to differentiate it from fungal intertrigo. A skin biopsy should be considered if the diagnosis is in doubt. In this case, the patient’s presentation was consistent with histological findings of inverse psoriasis, also known as flexural or intertriginous psoriasis.

Upon diagnosis by his dermatologist, the patient was treated with betamethasone valerate 0.1% cream nightly for 1 week, followed by topical tacrolimus 0.1% twice per week indefinitely. This treatment cleared up his psoriasis and resolved the associated itch, and appeared to keep the psoriasis at bay.