Multiple Myeloma: An Informative USMLE Guide

Introduction

Multiple Myeloma is a hematological malignancy characterized by the proliferation of abnormal plasma cells in the bone marrow. This USMLE guide aims to provide a comprehensive overview of multiple myeloma, including its etiology, clinical presentation, diagnosis, and management.

Etiology

Multiple myeloma is a complex disease with an unclear etiology. However, several risk factors have been identified:

• Age: Incidence increases with age, with most cases occurring in individuals over 65 years old.
• Gender: Males are slightly more prone to developing multiple myeloma.
• Race: African Americans have a higher incidence compared to other ethnic groups.
• Family history: Individuals with a first-degree relative affected by multiple myeloma have an increased risk.

Clinical Presentation

Multiple myeloma often presents with a combination of the following clinical features:

• Bone Pain: Due to osteolytic lesions leading to bone destruction.
• Fatigue: Anemia resulting from impaired production of normal blood cells.
• Recurrent Infections: Defective plasma cells compromise the immune system.
• Renal Dysfunction: Myeloma proteins can cause kidney damage.
• Hypercalcemia: Bone breakdown releases calcium into the bloodstream.

Diagnostic Approach

The diagnostic workup for multiple myeloma involves various laboratory tests and imaging studies:

• Serum Protein Electrophoresis (SPEP): Identifies monoclonal protein (M-protein) in the blood.
• Urine Protein Electrophoresis (UPEP): Detects monoclonal protein in the urine.
• Bone Marrow Aspiration and Biopsy: Confirms the presence of abnormal plasma cells.
• Imaging: Skeletal survey or whole-body MRI to assess for lytic bone lesions.

Diagnostic Criteria

Multiple myeloma can be diagnosed using the CRAB criteria:

• Calcium elevation (serum calcium >11 mg/dL).
• Renal dysfunction (serum creatinine >2 mg/dL).
• Anemia (hemoglobin <10 g/dL).
• Bone lesions (lytic lesions or osteoporosis).

Staging

Multiple myeloma can be staged using the International Staging System (ISS), which considers the β2-microglobulin level and albumin level.

Management

The management of multiple myeloma involves a combination of chemotherapy, immunomodulatory drugs, and supportive care:

• Chemotherapy: Incorporates proteasome inhibitors (e.g., bortezomib) and immunomodulatory drugs (e.g., lenalidomide).
• Autologous Stem Cell Transplantation: Reserved for eligible patients who achieve a response with initial treatment.
• Supportive Care: Bisphosphonates for bone protection, erythropoiesis-stimulating agents for anemia, and antimicrobial prophylaxis for infections.

Prognosis

The prognosis of multiple myeloma depends on several factors, including the patient's age, cytogenetic abnormalities, and response to treatment. The International Myeloma Staging System (IMSS) provides a risk stratification based on these factors, helping predict survival outcomes.

Conclusion

This USMLE guide provided an informative overview of multiple myeloma, covering its etiology, clinical presentation, diagnostic approach, management, and prognosis. Understanding the key concepts surrounding multiple myeloma is essential for medical students preparing for the USMLE examination.