Eosinophilic dermatosis of haematological malignancy (EDHM): A series of nine cases

Abstract Background Nonspecific cutaneous eruptions in patients with haematological malignancies are not uncommon. Eosinophilic dermatosis of haematological malignancy (EDHM), previously known as an ‘insect bite‐like’ reaction, has been reported in a wide range of haematological malignancies, most commonly chronic lymphocytic leukaemia. Its exact pathogenetic mechanism is unclear. Objectives To further characterise this eruption, review the literature of this rare condition and discuss its nosological status with respect to several differential diagnoses. Methods Nine patients with a diagnosis of EDHM were identified retrospectively and the clinical and histological features were reviewed. Results The morphology of the cutaneous eruptions varied between patients with macules, papules, nodules, vesicles or bullae all reported. Eight out of the nine cases had a known underlying malignancy. The cutaneous eruption preceded and led to the diagnosis of a splenic marginal zone lymphoma in one patient. Eosinophils were identified in all histological specimens. Other common features included bullae, lymphocytic infiltrates and apoptotic keratinocytes. CD20(+) B‐cells were only observed in one case. Conclusions We present a series of nine patients with EDHM associated with a range of haematological malignancies and with varied clinical presentations. The histological features however were consistent. We postulate potential mechanisms underlying the pathogenesis of this uncommon condition, which is most likely due to a dysregulated immune system driving a T‐cell and eosinophil‐mediated hypersensitivity reaction.