Erythrodermic crusted scabies-a diagnostic pitfall and mini-review: a case report

Erythroderma is a severe dermatologic condition with a broad differential diagnosis encompassing inflammatory, drug-induced, neoplastic, and infectious etiologies. Scabies is the most common neglected tropical disease (NTD) and can manifest in two common forms: classic and crusted types. Although rare, crusted scabies is an important and frequently underrecognized cause of erythroderma (accounting for <0.5% of cases) that poses diagnostic challenges due to its clinical overlap with other dermatoses associated with erythroderma.

We report the case of a 70-year-old man with a history of psoriasis who developed generalized erythroderma with pruritus and crusted, hyperkeratotic plaques on the face, scalp, and trunk. Skin biopsy demonstrated psoriasiform changes without detectable mites, whereas skin scrapings confirmed the presence of Sarcoptes scabiei, establishing the diagnosis of crusted scabies (erythrodermic crusted scabies). Differential diagnoses included psoriasis, adverse drug reaction, and seborrheic dermatitis. Treatment with oral ivermectin and topical scabicidal therapy resulted in marked clinical improvement. A review of the literature identified 16 reported cases of erythroderma secondary to scabies and highlighted the frequent misdiagnosis of this condition due to overlapping clinical and histopathological features, potentially delaying appropriate treatment and increasing the risk of complications.

This case highlights the importance of considering crusted scabies in patients presenting with erythroderma, pruritus, and hyperkeratotic or scaly lesions and supports the integration of clinical assessment with parasitological examination, particularly skin scrapings, to reduce the risk of misdiagnosis and facilitate timely management. This is particularly relevant in primary care and general practice settings, where initial management decisions are often made. Knowledge of various scabies manifestations, especially its erythrodermic presentation, could further improve disease management and control, particularly in endemic and resource-limited areas.