Unmasking Oligosecretory multiple myeloma: a case report highlighting diagnostic pitfalls

Oligosecretory multiple myeloma (OSMM) is a rare subtype of plasma cell dyscrasia that poses significant diagnostic challenges due to the absence of a clear monoclonal (M) spike on serum protein electrophoresis. We report the case of a 64-year-old woman with a history of ovarian tumor who presented with progressive fatigue, weight loss, bone pain, anaemia, hypercalcemia, and renal dysfunction. Despite the absence of a definitive M-spike, further immunochemical testing revealed discrete IgG-kappa bands on immunofixation, skeletal x-rays showed extensive osteolytic lesions. A bone marrow biopsy confirmed a diagnosis of OSMM. This case highlights the importance of considering oligosecretory variants in patients with clinical and radiological features suggestive of myeloma, even when routine tests appear normal, and illustrates how comprehensive evaluation with immunofixation and bone marrow examination can prevent diagnostic delays and allow timely initiation of treatment in these diagnostically challenging cases.