Chronic multifocal osteomyelitis, left humerus

This code signifies a persistent, widespread infection of the bone marrow and surrounding bone tissue in the left upper arm. It indicates an ongoing inflammatory process affecting multiple areas within the humerus, rather than a single, localized infection.

Apply this code when documentation clearly states chronic osteomyelitis affecting the left humerus, specifically noting its multifocal nature. Supporting documentation would include imaging reports (X-ray, MRI, bone scan) demonstrating multiple affected areas, along with clinical notes detailing persistent symptoms and treatment for a long-standing infection.

• Ensure documentation explicitly states "chronic" and "multifocal" to differentiate from acute or localized osteomyelitis.
• Verify laterality (left humerus) is clearly documented.
• Do not confuse with M86.321 (right humerus) or M86.329 (unspecified humerus).