Myeloma cast nephropathy

Cast nephropathy - 2 cropped - very high mag

Myeloma cast nephropathy is a medical condition affecting the kidneys, specifically associated with multiple myeloma, a type of blood cancer that originates in the plasma cells of the bone marrow. This condition is also known as myeloma kidney or cast nephropathy and is one of the most common causes of renal failure in patients with multiple myeloma.

Pathophysiology

The pathogenesis of myeloma cast nephropathy involves the overproduction of monoclonal immunoglobulin light chains by malignant plasma cells. These light chains are freely filtered by the glomerulus and are reabsorbed and catabolized by the proximal tubular cells of the kidneys. However, in multiple myeloma, the excessive production of light chains overwhelms the reabsorptive capacity of the renal tubules, leading to the presence of free light chains in the urine. These light chains can bind to Tamm-Horsfall protein, a type of mucoprotein secreted by the tubular cells, forming casts that obstruct the tubules, leading to tubular injury and, consequently, renal failure.

Clinical Features

Patients with myeloma cast nephropathy may present with various symptoms related to renal failure, including fatigue, nausea, vomiting, reduced urine output (oliguria), and edema. Laboratory findings may include elevated serum creatinine, hypercalcemia, anemia, and abnormal urine analysis showing proteinuria, specifically Bence Jones proteinuria, which is characterized by the presence of free light chains in the urine.

Diagnosis

The diagnosis of myeloma cast nephropathy is based on a combination of clinical presentation, laboratory findings, and renal biopsy. The biopsy shows characteristic findings of tubular casts with a fractured appearance, surrounded by giant cells and tubular atrophy. Immunofluorescence microscopy can detect the presence of monoclonal light chains within the casts.

Treatment

Treatment of myeloma cast nephropathy focuses on addressing the underlying multiple myeloma and improving renal function. This includes hydration, correction of hypercalcemia, and the use of therapies to reduce the production of light chains, such as chemotherapy or targeted therapies like bortezomib or lenalidomide. In some cases, dialysis may be necessary to manage severe renal failure.

Prognosis

The prognosis of patients with myeloma cast nephropathy varies and is closely linked to the control of the underlying multiple myeloma and the extent of renal recovery. Early diagnosis and treatment are crucial for improving outcomes.