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Case Report: Hypereosinophilic syndrome misdiagnosed as atopic dermatitis due to refractory pruritic rash masking peripheral neuropathy

Li H, Yang X, Zhang C, Zhu W, Jia H

Frontiers in medicine, 2026

Abstract

Background: Hypereosinophilic syndrome (HES) is a rare and heterogeneous disorder characterized by persistent eosinophilia and multi-organ involvement. Cutaneous manifestations are common, whereas peripheral neuropathy may be underrecognized, particularly when dermatologic symptoms predominate.

Case presentation: We report the case of a 49-year-old man with a 10-year history of recurrent pruritic papules initially managed as atopic dermatitis. Laboratory testing revealed marked eosinophilia (absolute eosinophil count: 5.29 × 109/L) and significantly elevated total immunoglobulin E (IgE) (>6,000 IU/mL; reference range: 0-100 IU/mL). One week after initiating upadacitinib for refractory pruritus, the patient's itch severity decreased substantially, after which he more clearly perceived distal numbness and gait instability. Nerve conduction studies demonstrated a symmetric sensory-predominant axonal polyneuropathy. Skin biopsy showed eosinophilic inflammatory infiltration without evidence of vasculitis. Quantitative intraepidermal nerve fiber density (IENFD) was within the age-adjusted reference range, consistent with preserved small-fiber integrity. After comprehensive exclusion of secondary and clonal causes of eosinophilia, a diagnosis of idiopathic HES with cutaneous and peripheral nervous system involvement was established. Treatment was adjusted to mepolizumab (300 mg subcutaneously every 4 weeks), followed by clinical improvement in neuropathic symptoms and a reduction…

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