IgM-λ paraproteinemia with associated cutaneous lymphoplasmacytic infiltrate in a patient who meets diagnostic criteria for POEMS syndrome

POEMS is a rare multisystem paraneoplastic syndrome featuring polyneuropathy, organomegaly, endocrinopathy, a monoclonal protein, and skin changes. In the relatively few reported biopsies of POEMS-associated cutaneous hyperpigmentation, the most common skin finding seen in patients with the disorder, only a non-specific inflammatory infiltrate has been demonstrated histologically. We present the case of a 79-year-old man with polyneuropathy, autoimmune thyroiditis, pancytopenia, and a history of lymphadenopathy who presented to the inpatient dermatology service with cutaneous hyperpigmentation. A skin biopsy of a hyperpigmented area showed a cutaneous lymphoplasmacytic infiltrate, prompting further investigation. A monoclonal IgM-λ paraprotein was subsequently identified, leading to administration of combination chemotherapy for a diagnosis of POEMS syndrome. The novel finding of a lymphoplasmacytic infiltrate in POEMS-associated hyperpigmentation suggests a diagnostic role for skin biopsy in these patients.