ICD-10 Code C90.12 – Plasma cell leukemia in relapse (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C90.12 – Plasma cell leukemia in relapse
What it is
C90.12 identifies plasma cell leukemia that has returned after a prior period of response or remission. Use it when the record clearly documents relapse of this aggressive plasma cell disorder.
Clinical signs
Clinical features vary; refer to documentation. Common findings may include circulating plasma cells, anemia, thrombocytopenia, bone pain, fatigue, and other signs of advanced plasma cell disease.
When to use this code
Use C90.12 when the clinician states plasma cell leukemia has relapsed, recurrent, or returned after prior treatment. The diagnosis should be documented as active disease, not just a history of plasma cell leukemia. If the note only says “follow-up” or “status post,” check documentation.
Do not use for
Do not use this code for newly diagnosed plasma cell leukemia without relapse, or for multiple myeloma without leukemia involvement. Do not assign it when relapse is not documented; check documentation.
Coding tip
Look for explicit terms such as “relapsed,” “recurrent,” or “in relapse” in the assessment or problem list before coding C90.12.