Title: Hidden in Plain Sight: Delayed Diagnosis of Multiple Myeloma Presenting as Recurrent Rib Pain

Author(s): Michael Edward Abundo MS, MD; Rupalakshmi Vijayan MS,MD; Theresanne DeMartino Ringler, DO; Sumira A Koirala, MD

First Author Email: mabundo@mercy.com

Institution: SEBH

Residency: Family Medicine (SEBH)

Introduction: Multiple myeloma (MM) prevalence is increased in males and African Americans with a median age of about 65 years [1-4]. MM symptoms can include anemia, renal failure, hypercalcemia, lytic bone lesions, and at times can have some clotting abnormalities, neurologic symptoms, and hyperviscosity [1-2, 5]. Since symptoms can be wide and varied, it can be misattributed to common diagnosis including but not limited to musculoskeletal conditions, which can lead to delayed diagnosis. Classification of high-risk MM continues to evolve from the phenotypic manifestation of disease in addition to genomic markers that can affect mortality [6-7]. In our case report we will discuss our patient who was diagnosed with light chain MM (LCMM) with a high-risk genomic feature, gain of 1q. LCMM accounts for 15% of MM cases where the clonal plasma cells are unable to produce heavy chains, as a consequence light chains are over produced [8]. The most common clinical presentation of LCMM includes renal failure, bone disease,and a systemic light chain amyloidosis which contributes to its aggressive course and poorer prognosis once compared to other types of MM, making prompt diagnosis critical.[8].

Case Report: A 64-year-old man with a history of hyperlipidemia and constipation presented with a one-year history of intermittent, atraumatic left-sided rib pain. Symptoms temporarily improved following brief courses of chiropractic manipulation. He later developed acute worsening rib and back pain unresponsive to conservative care, prompting urgent evaluation. Chest radiography in urgent care revealed an expansile lytic lesion of the left rib and concerns for pathologic fracture. Case Assessment and biopsy analysis Laboratory evaluation demonstrated an IgM monoclonal lambda paraprotein, urine monoclonal free lambda light chains, and markedly elevated serum free lambda chains (>4,000 mg/L), consistent with plasma cell dyscrasia. CT imaging revealed multiple lytic lesions involving ribs and thoracolumbar vertebrae. Review of prior imaging obtained seven months earlier for nephrolithiasis showed missed early skeletal changes. Of note bone biopsy with a CD 138 immunohistochemical staining of the core biopsy showed 60% plasma cells with both in-situ hybridization and flow cytometry showing lambda restriction in the plasma cells, consistent with plasma cell myeloma. Plasma cell enriched FISH analysis shows monosomy 13, gain of 1q, trisomies 5,9, and 15; and IgH rearrangement. Due to limited samples IgH rearrangement could not be determined, moreover a gain of 1q is associated with a more unfavorable prognosis of myeloma [7].

Discussion/Conclusion: This case emphasizes the importance of recognizing treatment failure in musculoskeletal pain, when clinical suspicion should lead to a more in-depth evaluation. Keeping an open diagnosis is paramount in assuring that serious underlying disease processes are not missed. Multidisciplinary communication and heightened clinical suspicion are critical to improving outcomes in multiple myeloma through early imaging and laboratory evaluation.