A case of eosinophilic dermatosis of haematological malignancy in an immunocompromised patient

A 51-year-old man with a 3-year history of chronic lymphocytic leukaemia (CLL) presented to the dermatology department with a polymorphic rash, 3 months after receiving a trial combination treatment for CLL, consisting of dexamethasone, lenalidomide and ofatumumab. The rash was mainly indurated plaques; a biopsy showed an interstitial granulomatous reaction thought to be consistent with a drug reaction, which failed to respond to topical betamethasone valerate 0.1%. The patient was started on 30 mg daily prednisolone, and then additionally required clobetasol propionate 0.1% under PB7 bandages; this combination was continued for 10 weeks. The patient continued to develop new lesions, which were more nodular in appearance, particularly on the lower legs, with some blisters. A further biopsy showed an eosinophil-rich infiltrate, and a diagnosis of an eosinophilic dermatosis of haematological malignancy was given. As there were vast numbers of eosinophils the patient was referred to the infectious diseases unit. Here, a full battery of tests was carried out, including serology for HIV, syphilis and hepatitis, and a stool culture. All tests were negative and therefore an infectious cause was ruled out. Given the amount of eosinophils, bullous pemphigoid was also raised as a possible diagnosis; however, antiepidermal antibodies were negative. Currently, the patient is on 100 mg dapsone and a reducing course of prednisolone. Eosinophilic dermatosis of haematological malignancy has been described in association with haemoproliferative disorders, particularly CLL. It can be polymorphic in presentation: erythema, papules, urticarial and nodular eruption. There is debate about whether this is an 'exaggerated insect bite reaction'; however, many of the patients deny ever being bitten by an insect. Histology normally shows an eosinophilic, superficial and deep mixed inflammatory cell infiltrate. There are a number of cutaneous manifestations of CLL. The following criteria have been proposed for the diagnosis of eosinophilic dermatoses: (i) pruritic papules/nodules or vesiculobullous eruption; (ii) eosinophilrich superficial and deep dermal lymphohistiocytic infiltrate on histopathology; and (iii) exclusion of other causes of tissue eosinophilia. The skin lesions can appear months to years after diagnosis but can occasionally precede the diagnosis. A number of dermatoses resemble eosinophilic dermatoses of haematological malignancy, including leukaemia cutis, scabies, drug eruption, insect bite reaction and papular urticaria.