Eosinophilic dermatosis of haematologic malignancy treated with ibrutinib: A case report

Abstract Eosinophilic dermatosis of haematologic malignancy is an infrequent skin disorder characterised by severe pruritus and skin lesions resembling arthropod bites. It primarily affects individuals with underlying haematological conditions, most commonly chronic lymphocytic leukaemia (CLL). While it does not correlate with a worse prognosis for the haematological disease itself, it significantly impacts patients' quality of life due to the distressing pruritus and recurring nature. Clinical presentation typically shows erythematous papules resembling arthropod bites, with less frequent occurrences of urticarial plaques or bullous lesions. Histologically, an intense and polymorphous inflammatory infiltrate is found both in the superficial and deep dermis, marked by an abundance of eosinophils and the absence of atypical cells. Treatment of this disease remains uncertain, with corticosteroids often being the only effective therapy. Here, we present the case of an 80‐year‐old patient with a history of CLL, who experienced a widespread, itchy eruption of papules and plaques over 2 months. Despite various therapeutic attempts, the lesions only responded to high‐dose corticosteroids. Following the initiation of ibrutinib at a daily dose of 420 mg, both the skin lesions and pruritus resolved within 3 months. Ibrutinib, a tyrosine kinase inhibitor, is approved as a first‐line treatment for CLL. However, its potential as a remedy for refractory eosinophilic dermatosis has not been reported thus far.