ICD 10 Coding Alert

Question: I am trying to locate the correct ICD-10-CM code for smoldering multiple myeloma (SMM). As the note doesn’t indicate CRAB symptoms (elevated calcium levels; renal failure; anemia; bone lesions), I don’t believe it should be coded in the C90 codes for multiple myelomas, and I don’t think it fits the bill for monoclonal gammopathy of unknown significance (MGUS). What is the correct code for the condition?

AAPC Forum Participant

Answer: The National Cancer Institute says on its website: “Smoldering myeloma is a precancerous condition that alters certain proteins in blood and/or increases plasma cells in bone marrow, but it does not cause symptoms of disease. About half of those diagnosed with the condition, however, will develop multiple myeloma within 5 years.”

This means SMM is linked to multiple myeloma but is not coded to any of the C90 (Multiple myeloma and malignant plasma cell neoplasms) codes, as you correctly note. Consequently, as SMM is considered precancerous and not classified as a malignant neoplasm, you code it to D47.2 (Monoclonal gammopathy), according to AHA ICD-10-CM Coding Clinic Volume 8, No. 3 (2021).

Additionally, you are correct in thinking the condition is distinct from MGUS in that patients with smoldering myeloma have more than 10 percent plasma cells in their bone marrow — enough that the condition can be classified as myeloma but without the CRAB symptoms you mention — whereas patients with MGUS do not have the amount of plasma cells to classify the condition as myeloma, according to the Institute for Myeloma & Bone Cancer Research (IMBCR) (https://imbcr.org/myeloma/). However, MGUS is an inclusion term for D47.2, so you would use the code for both SMM and MGUS.