Case Presentation: Multiple myeloma (MM) is a rare hematologic malignancy characterized by abnormal growth of plasma cells in the bone marrow, which produce large amounts of either a single type of antibody (i.e. monoclonal immunoglobulins) or parts of an antibody (i.e. light chains). Classically, MM is evaluated based on the CRAB criteria: elevated serum calcium, kidney dysfunction, low red blood cells (anemia), and bone lesions—often accompanied by fatigue, recurrent infections, and axial skeletal pain [1]. In 2014, the framework was extended to include the SLiM criteria: ≥60% clonal bone marrow plasma cells, a serum light chain ratio >100 (I/U), and at least one bony lesion >5mm on MRI [2,3].We report the case of a 63-year-old Caucasian female with vitamin D deficiency who presented to the emergency department in April 2025 with a L1 compression fracture. She returned in July with worsening, unprovoked, 10/10 low back pain. Review of systems noted constipation, nausea, weight loss. The exam showed point tenderness over the thoracic spinous processes. Admission labs revealed Cr 0.60 mg/dL, eGFR > 90 mL/min/1.73 m2, Ca²⁺ 0.6 mg/dL, Hgb 12.9 g/dL, albumin 3.8 g/dL, and total serum protein 8.3 g/dL. Vitamin D was 51 ng/dL and urine protein was 14 mg/dL. Despite the lack of anemia, hypercalcemia, and renal impairment, MM was still a differential diagnosis due to a protein gap >4 [4]. X-ray demonstrated a T11 compression fracture with osteopenia. CT of the lumbar and thoracic spine additionally unveiled an unmeasured lytic lesion on the T12 pedicle. While being moved onto the CT machine, the patient felt significant right rib pain, and additional CT thorax completed two days later confirmed unprovoked 7/8th anterior rib fractures and innumerable small lytic lesions diffusely scattered across the ribcage.Subsequent labs revealed IgG kappa monoclonal immunoglobulin of 2100 mg/dL and urine immunofixation (IgG kappa and excess free kappa light chain monoclonal immunoglobulins) < 10% of total urine protein. Biopsy of the lytic lesion confirmed a plasma cell neoplasm (CD 138+), and bone marrow biopsy revealed >10% clonal plasma cells, consistent with MM.
Discussion: This case highlights the importance of recognizing MM beyond its classical CRAB features, especially in the hospital setting where patients may present with nonspecific complaints. Despite the absence of anemia, renal dysfunction, or hypercalcemia, her extensive skeletal findings and significant protein gap warranted further investigation. SLiM criteria played a crucial role in raising early clinical suspicion, particularly in the context of normal laboratory parameters. With greater access to resources and ability to coordinate timely diagnostic workups, hospitalists are uniquely positioned to identify acute, atypical presentations. A comprehensive diagnostic approach—incorporating imaging, protein studies, and biopsy—was essential to confirm this diagnosis. Although more invasive due to the need for a bone marrow biopsy, recent research supports prioritizing the SLiM criteria for earlier detection of MM, potentially improving patient outcomes [3].
Conclusions: This vignette underscores the importance of using the SLiM criteria as a clinical framework when evaluating multiple myeloma. It highlights the need for hospitalists to adopt updated frameworks to recognize serious conditions that may not fit classical presentations.