Recurrent Hypoglycemia and Hypercalcemia As Presenting Features of CD30-Positive Peripheral T-cell Lymphoma, Not Otherwise Specified

Peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS), is an aggressive mature T-cell neoplasm that may present with nonspecific systemic and metabolic abnormalities. A 73-year-old man with type 2 diabetes mellitus presented with progressive weakness, altered mental status, recurrent hypoglycemia, and hypercalcemia, accompanied by acute kidney injury, pancytopenia, diffuse lymphadenopathy, and splenomegaly. A complete critical-sample evaluation during hypoglycemia was unavailable, and the mechanism of the parathyroid hormone (PTH)-independent hypercalcemia could not be established because PTH-related peptide and vitamin D metabolite measurements were unavailable. Core biopsy of a left axillary lymph node demonstrated a mature CD4-positive T-cell lymphoma with strong diffuse CD30 expression, reduced CD7, negative anaplastic lymphoma kinase and Epstein-Barr virus-encoded RNA studies, and a Ki-67 proliferation index exceeding 90%, supporting PTCL-NOS after exclusion of other supported mature T-cell lymphoma entities. Classification remained limited by the absence of an excisional biopsy and additional molecular studies. Prednisone cytoreduction was followed by cyclophosphamide, doxorubicin, and prednisone, with brentuximab vedotin planned but not documented as administered. The course was complicated by profound myelosuppression, Klebsiella pneumoniae pneumonia, and neutropenic septic shock. Formal response assessment was not possible because complete staging and adequate follow-up were unavailable. This case highlights the importance of prompt tissue diagnosis when unexplained metabolic abnormalities coexist with cytopenias and generalized lymphadenopathy. Although hypoglycemia and hypercalcemia occurred in association with PTCL-NOS, the available data do not establish a causal or paraneoplastic relationship.