A Classic Cutaneous Presentation of Thymoma-Associated Multiorgan Autoimmunity and Review of the Literature

ABSTRACT: Thymoma-associated multiorgan autoimmunity (TAMA) is a rare paraneoplastic syndrome characterized by graft-versus-host disease (GVHD)-like manifestations. The disorder is thought to arise from a disruption to central immune tolerance of T cells secondary to neoplastic growth of thymic epithelial cells. Thymic epithelial cells are crucial in T-cell education: distinguishing between self-antigens and foreign antigens. This process relies on a protein, the autoimmune regulator (AIRE), which negatively selects and eliminates T cells that are self-reactive. With neoplastic transformation of thymic cells, these cells may exhibit reduced AIRE, leading to an overabundance of autoreactive T cells. These autoreactive T cells mediate the sequelae of the GVHD-like presentation, with skin, liver, and gastrointestinal tract manifestations. We describe a case of a 74-year-old patient with a medical history of thymoma and multiple autoimmune conditions, who presented for diffuse psoriasiform eruption of the trunk and back. Skin biopsy further revealed epidermal hyperplasia with interface change, extensive dyskeratosis, and numerous apoptotic keratinocytes within parakeratotic scale, including striking involvement of the follicular epithelium. Our patient developed hepatobiliary and cholestasis injury, with rising bilirubin, AST, and ALT levels. Despite therapeutic modifications, his cutaneous and systemic disease progressed, and he died approximately 1 month after the diagnosis of TAMA due to complications of small bowel obstruction. This case highlights the pressing need for heightened clinical suspicion and a multidisciplinary team approach when presented with a thymoma patient.