Eosinophilic Dermatosis of Hematologic Malignancy
Joya Sahu
Jason B. Lee
Eosinophilic dermatosis may be encountered in the setting of various hematologic malignancies and hematologic disorders, including blood dyscrasias and myelodysplastic syndromes. Eosinophilic dermatosis has been most frequently described in association with chronic lymphocytic leukemia (CLL). Previously designated as insect bite–like reaction and eosinophilic dermatosis of myeloproliferative disease, this rare and refractory dermatosis presents as a pruritic, papulovesicular eruption associated with an eosinophil-rich infiltrate on biopsy. Although clinical and histopathologic features may be indistinguishable from insect bites, affected patients often have no history of them. The rarity of this condition and the conditions that simulate eosinophilic dermatosis of hematologic malignancy (EDHM) present a diagnostic and therapeutic challenge.
A variety of cutaneous eruptions have been reported in CLL, one of the most common hematologic malignancies. These have been classified as either “specific” or “nonspecific” lesions. Cutaneous leukemic cell infiltration or leukemia cutis is a specific type of manifestation confirmed histologically and presents clinically as violaceous or reddish-brown papules or nodules in 8.3% of CLL patients. Nonspecific refers to nonmetastatic, secondary lesions which can be of infectious, hemorrhagic, or hypersensitive origin.1,2 Forty-five percent of CLL patients will experience a nonspecific dermatosis, including petechiae, purpura, urticaria, erythema multiforme, exfoliative dermatitis, paraneoplastic pemphigus, vasculitis, and eosinophilic dermatosis.1,2,3,4,5 EDHM or insect bite–like reaction is a rare cutaneous eruption reported most often in CLL patients presenting as a papulovesicular eruption, clinically and histopathologically mimicking insect bites and other eosinophil-rich dermatoses.3,5,6 EDHM has been described in other hematologic malignancies, primarily in patients with B-cell hematologic malignancies such as mantle cell lymphoma, acute lymphoblastic leukemia, and large cell lymphoma, as well as in acute monocytic leukemia and myelofibrosis.3,7,8,9,10 It is now increasingly accepted that this entity can also be seen in patients with blood dyscrasias as well as myelodysplastic syndromes, and as such, EDHM remains a suitable, all-encompassing term.
HISTORICAL PERSPECTIVE
EDHM was first conceptualized by Weed11 in 1965 as an insect bite–like reaction observed in patients with CLL. Although ∼40 cases of EDHM in patients with CLL have been since reported, this phenomenon is most probably underrecognized and underreported.1 Although initially thought to be a specific hypersensitivity reaction to insect bites, particularly mosquitoes,11,12,13 most CLL patients deny a history of insect bites, and thus the term “insect bite–like reaction” was coined.3 Byrd et al.14 further defined this process as “eosinophilic dermatosis of myeloproliferative disease,” and proposed defining criteria: (a) pruritic papules, nodules, and/or vesiculobullous eruption refractory to standard treatment; (b) eosinophil-rich superficial and deep dermal lymphohistiocytic infiltrate on histopathology; (c) exclusion of other causes of tissue eosinophilia; and (d) diagnosis of hematologic malignancy.
EPIDEMIOLOGY
Although limited, most case reports of EDHM generally corroborate these clinical, histopathologic, and immunologic criteria. CLL patients tend to present with EDHM in the fifth to seventh decade of life. Eruptions occur concurrently or months to years after CLL diagnosis, but on occasion EDHM can precede CLL diagnosis. EDHM most frequently presents as pruritic papules, nodules, and vesicles/bullae resembling insect bites occurring on both exposed and nonexposed areas of the body including the face, trunk, and extremities (Figs. 57-1, 57-2 and 57-3). Lesions are often indurated, erythematous, and may be tender.1,3,6,7,15,16,17,18,19,20 No discernible relationship with outdoor activity or seasonal changes can be identified, and a history of insect bites cannot be elicited.3,6,15,17
 FIGURE 57-1. Excoriated, edematous, erythematous papules on the face. |
 FIGURE 57-2. Multiple erythematous urticarial papules and plaques on the shoulder and arm. |
 FIGURE 57-3. Numerous intact erythematous papules and excoriated papules on the upper back. |
HISTOLOGY
In EDHM, increased numbers of eosinophils are seen in association with a superficial and/or deep perivascular lymphocytic infiltrate, which may have both a concurrent interstitial lymphocytic component and prominent adnexal and hair follicle involvement (Figs. 57-4 and 57-5). Papillary dermal edema, eosinophilic spongiosis, a wedge-shaped infiltrate, and follicular mucinosis of involved hair follicle units can commonly be found (Fig. 57-6). These features often lead to the misdiagnosis of insect bite reaction or eosinophilic folliculitis. The presence of excoriation or ulceration compounds diagnostic confusion owing to the additional presence of neutrophils.
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