ICD-10 code for Polymyositis

The ICD-10-CM code for Polymyositis is M33.20 (Polymyositis, organ involvement unspecified). The official index lists 3 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on M33.20.

Within M33.2, choose M33.20 (organ involvement unspecified) only when documentation doesn't support a more specific option: with respiratory involvement (M33.21), with myopathy (M33.22) and with other organ involvement (M33.29).

As a secondary diagnosis it is a CC (complication or comorbidity), which can move an inpatient stay into the "with CC" MS-DRG of its family, unless the principal diagnosis excludes it.

In MS-DRG v44.0, it is part of the grouping logic for DRG 545 (Connective Tissue Disorders with MCC, relative weight 2.3892), DRG 546 (Connective Tissue Disorders with CC, relative weight 1.1745) and DRG 547 (Connective Tissue Disorders without CC/MCC, relative weight 0.7526), in MDC 08 (Diseases and Disorders of the Musculoskeletal System and Connective Tissue), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.