Multiple Myeloma Diagnosis and Characteristics
Primary Symptoms and Laboratory Abnormalities
- The International Myeloma Society recommends that multiple myeloma be diagnosed based on the presence of CRAB criteria, which include hypercalcemia, renal insufficiency, anemia, and bone lesions 1, 2
- Hypercalcemia is characterized by serum calcium >11.5 mg/dL, which can cause symptoms such as polyuria, gastrointestinal disturbances, progressive dehydration, and decreased glomerular filtration rate 1, 3
- Renal insufficiency is defined as serum creatinine >2 mg/dL or estimated creatinine clearance <40 mL/min, often presenting as mild increases in serum creatinine with or without nonselective proteinuria 1, 2
- Anemia is characterized by normochromic, normocytic anemia with hemoglobin <10 g/dL or ≥2 g/dL below the lower limit of normal, manifesting as weakness, fatigue, and pallor 1, 2
- Bone lesions are characterized by lytic lesions, severe osteopenia, or pathologic fractures, typically presenting as bone pain or pathologic fractures 1, 2
- The presence of monoclonal protein (M-protein) ≥3 g/dL in serum or abnormal free light chains in urine is a key laboratory abnormality in multiple myeloma 1, 7
- Bone marrow plasma cells ≥10% is another key laboratory abnormality in multiple myeloma 1, 7
Differential Diagnosis
- The American Society of Clinical Oncology recommends distinguishing multiple myeloma from other conditions, such as Monoclonal Gammopathy of Undetermined Significance (MGUS) and Smoldering Multiple Myeloma (SMM) 1, 7
- MGUS is characterized by M-protein <3 g/dL, bone marrow plasma cells <10%, and absence of end-organ damage 1, 7
- SMM is characterized by M-protein ≥3 g/dL and/or bone marrow plasma cells ≥10%, but absence of end-organ damage 1, 7
- Primary Systemic Amyloidosis (AL) may present with substantial albuminuria, congestive heart failure, renal failure, peripheral neuropathy, orthostatic hypotension, carpal tunnel syndrome, hepatomegaly, or malabsorption syndrome 4, 5