Graft-Versus-Host Disease-like Erythroderma in the Setting of Thymoma: A Rare Paraneoplastic Disorder

We present a case of graft-versus-host disease (GVHD)-like erythroderma related to thymoma-associated multiorgan autoimmunity (TAMA), a rare paraneoplastic syndrome. A 45-year-old woman with a history of a recent thymoma resection was admitted to the intensive care unit for erythroderma. The erythroderma had progressed over 6 months from a scaling, pruritic rash on bilateral forearms despite treatment with topical corticosteroids. Dermatologic evaluation showed scaly, hyperkeratotic plaques covering greater than 90% of total body surface area. Biopsy taken during admission showed epidermal verrucous acanthosis with parakeratosis and interface vacuolar change, and necrotic keratinocytes within the epidermis accompanied by superficial dermal lymphocytes with foci of exocytosis and dermal pigment incontinence with few eosinophils. Pathological findings and clinical correlation led to the diagnosis of GVHD-like erythroderma related to TAMA. She responded well to cyclosporine and was switched to tacrolimus before discharge. Punch biopsy after several months of treatment with tacrolimus showed improvement with milder interface dermatitis and reduction in necrotic keratinocytes. There is no standard treatment regimen for cutaneous manifestations of TAMA, and prognosis is poor in the reported cases. There are shared histopathologic findings with classic cutaneous GVHD unrelated to thymoma as well as other erythrodermic entities including drug eruptions and connective tissue diseases. The nonspecific histopathologic findings of GVHD-like erythroderma related to TAMA and the lack of established diagnostic criteria illustrate the necessity of clinicopathologic correlation for correct diagnosis when evaluating erythroderma of undifferentiated etiology.