Bilateral hand-restricted drug eruption induced by blonanserin: a case report

Cutaneous adverse drug reactions due to antipsychotic therapy are well-documented, although their manifestations are highly variable. Blonanserin, a second-generation antipsychotic, is generally considered to have a favorable tolerability profile. Cutaneous reactions to blonanserin are rare and, more importantly, remain poorly characterized. This case report describes a novel and distinctive presentation of a bilateral hand-restricted drug eruption attributed to blonanserin.

A 26-year-old woman without prior psychiatric history was hospitalized for an acute psychotic episode. Treatment was initiated with quetiapine (25 mg at bedtime), and blonanserin (8 mg/day) was added on the fifth hospital day to accelerate symptom control. On the fourth day of combination therapy, the patient developed symmetrical, erythematous papules limited to the dorsal and palmar aspects of both hands, with no history of new topical exposures. Although the rash was initially managed as dyshidrotic eczema or contact dermatitis with antihistamines and potent topical corticosteroids, it worsened over the following week. Given the strong temporal relationship, blonanserin was discontinued on the tenth day after rash onset, while quetiapine was continued. A dramatic improvement was observed within 72 hours, with near-complete resolution within one week. The patient's psychiatric symptoms remained stable on quetiapine monotherapy.

This is the first report of a bilateral hand-limited drug eruption due to blonanserin and underscores that prompt withdrawal upon rash appearance is important for patient comfort and aligns with good clinical practice.