Non-Secretory Multiple Myeloma with Patchy Marrow Involvement and Aberrant Cytokeratin Expression

Non-secretory multiple myeloma is a rare form of the disease that presents a diagnostic challenge. A 69-year-old woman presented to the emergency department with a pathological fracture of the right clavicle, along with a history of asthenia and middle back pain in the preceding three months. Workup revealed multiple focal lytic bone lesions in the clavicles, ribs, skull and thoracic- lumbar-sacral spine, without evidence of anemia, hypercalcemia or renal failure, with no abnormal immunofixation in the serum or urine and with normal serum free light chain ratios. The Iliac crest bone marrow aspiration and biopsy revealed a scarcely involved marrow, However, biopsy of one of the focal bone lesions revealed a hypercellular bone marrow with phenotypically abnormal plasmocytes, along with an intriguing, albeit aberrant, cytokeratin expression. Non-secretory multiple myeloma is in itself a rare diagnosis. However, the combination of a patchy marrow involvement and aberrant cytokeratin expression makes this a noteworthy presentation.