A report describes a case of a 45-year-old male, who was a known case of psoriasis on remission, presented with generalized erythema and scaling for 1 month. He gave a history of self-prescribed steroids, antibiotics and topical salicylic acid formulations, which provided only temporary relief. Examination revealed diffuse, hyperkeratotic, yellow scales on an erythematous base, shielding 95% body surface area. 

Based on the features, a provisional diagnosis of psoriatic erythroderma was made. 

Histology of 10% potassium hydroxide (KOH) mount of scales showed 5 to 6 scabies mites/high power field. Serum cortisol level at 08:00 hours was found to be much lower at 0.3 μg/dL. Other investigations like complete hemogram, liver function test, kidney function test, random blood sugar, glycosylated hemoglobin, viral markers, urine routine microscopy, chest X-ray and ECG were nonsignificant. 

Thus, a diagnosis of erythroderma secondary to crusted scabies with iatrogenic Cushing’s disease (because of self-prescribed steroid) was made. 

He was given oral ivermectin (200 µg/kg) on days 1, 2, 8, 9 and 15, along with 5% permethrin cream which was to be applied daily for 7 days followed by twice-weekly application until no mite was detected on KOH mount.

His hyperkeratotic plaques cleared after 3 weeks. For iatrogenic Cushing’s disease, physiological doses of tablet prednisolone 5mg in the morning and 2.5mg in the evening were initiated as advised by the endocrinologist.

Source: Devi GC, Hazarika N. Erythroderma secondary to crusted scabies. BMJ Case Rep. 2021;14(12):e248000.