A 42-Year-Old With Back Pain After Traveling

Discussion

A middle-aged man with low back pain is a common clinical scenario; this condition affects at least 20% of this age population.^[1] Less than 1% of these patients have a malignant cause.^[2] Red flags in this case included the persistence and worsening of back pain, which woke the patient up from sleep; systemic symptoms of fatigue; occasional fever; and hematologic and biochemical abnormalities on screening tests.

The diagnosis of multiple myeloma (MM) was suspected on the basis of a constellation of findings referred to by the acronym CRAB: calcium elevation with renal dysfunction, anemia, and backache or bone pain.^[3] All four criteria need not be present for a diagnosis to be made.^[4] The median age at diagnosis is 68 years; however, it is possible among younger adults as well.^[5] The nonspecific presentation of this disease often leads to significant delays in diagnosis.^[6]

In this case, an MRI of the spine revealed several lesions larger than 5 mm and involving multiple vertebral bodies; this helped confirmed the diagnosis. The diagnosis was supported by the markedly elevated ESR (> 100 mm/hr), which is found in MM and other cancers, autoimmune disorders, and infections. Clumping of red cells on peripheral blood smear (rouleaux formation) was also supportive of the diagnosis, although it may also be seen with systemic inflammation or the presence of red cell antibodies.

Plasma cells normally produce immune globulin. In MM, a malignant plasma cell clone secretes large amounts of abnormal heavy and/or light chain proteins, which are detectable in the blood or urine.^[3] In most cases, heavy chains are produced, and a monoclonal protein (M protein) can be detected on serum protein electrophoresis (SPEP); however, this is not specific and is sometimes found in lymphoid cancers (eg, Waldenström macroglobulinemia, chronic lymphocytic leukemia).^[7] SPEP findings were negative in this patient. However, an MRI of the spine revealed multiple bony lesions. No soft-tissue swelling was seen. A bone marrow aspirate confirmed the presence of 22% plasma cells. Test results for serum free light chains were later found to be positive; 20% of patients with MM only secrete light chains.^[8] Light chains can also be detected in the urine, where they are known as "Bence-Jones proteins," as was the case with this patient.

The International Myeloma Working Group (IMWG) criteria for MM specify that bone marrow aspirate or biopsy must show clonal bone marrow plasma cells of more than 10% or biopsy-proven bony or extramedullary plasmacytoma.^[4,9] One or more of the following must also be present:

• Evidence of end-organ damage that can be attributed to the underlying plasma cell proliferative disorder, specifically:

  • Hypercalcemia: serum calcium level > 0.25 mmol/L (> 1 mg/dL) higher than the upper limit of normal or > 2.75 mmol/L (> 11 mg/dL)

  • Renal insufficiency: Creatinine clearance < 40 mL/min or serum creatinine level > 177 µmol/L (> 2 mg/dL)

  • Anemia: hemoglobin level > 2 g/dL below the lower limit of normal or a hemoglobin level < 10 g/dL

  • Bone lesions: one or more osteolytic lesions on skeletal radiography, CT, or PET-CT

• Any one or more of the following biomarkers of cancer:

  • 60% clonal bone marrow plasma cells

  • Involved/uninvolved serum-free light chain ratio > 100

  • One or more focal lesion on MRI studies (each focal lesion must be > 5 mm)

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Cite this: Ankit Raiyani, Vikramjit Kanwar. A 42-Year-Old With Back Pain After Traveling - Medscape - Jul 10, 2023.