In simple words: Multiple myeloma is a type of blood cancer where abnormal plasma cells, which are part of the immune system, build up in the bone marrow. These abnormal cells crowd out healthy blood cells and produce abnormal proteins that can cause problems like bone pain, kidney damage, and infections.

Multiple myeloma, also known as Kahler's disease, is a cancer of plasma cells, a type of white blood cell that produces antibodies to fight infection. In multiple myeloma, cancerous plasma cells accumulate in the bone marrow, crowding out healthy blood cells and producing abnormal proteins that don't function properly. This can lead to various complications, including bone pain, anemia, kidney problems, and increased susceptibility to infections. The abnormal plasma cells also produce an M protein, which can further contribute to health issues.

Example 1: A 65-year-old patient presents with persistent bone pain, fatigue, and recurrent infections. Blood tests reveal anemia and elevated calcium levels. A bone marrow biopsy confirms the diagnosis of multiple myeloma., A 70-year-old patient experiences unexplained weight loss, weakness, and kidney problems. Urine tests show the presence of M protein. Further investigations, including a bone marrow biopsy, lead to a diagnosis of multiple myeloma., A 55-year-old patient with a history of monoclonal gammopathy of undetermined significance (MGUS) develops new symptoms, including bone pain and anemia. A bone marrow biopsy reveals an increase in plasma cells, confirming the progression to multiple myeloma.

Proper documentation for C90 requires detailed clinical findings, including symptoms like bone pain, fatigue, and infections. Laboratory results, such as blood counts, serum protein electrophoresis, and urine protein electrophoresis, are essential. Imaging studies like X-rays, CT scans, or MRI scans of affected bones are also necessary. Bone marrow biopsy results confirming the presence of abnormal plasma cells are crucial for diagnosis confirmation. Documentation of the stage of the disease and any associated complications, such as kidney damage or hypercalcemia, is also important.