M33.2

Clinical Information

• An idiopathic inflammatory disorder affecting the muscles. It presents with symmetrical proximal muscle weakness and elevated skeletal muscle enzymes.

• An inflammatory disease of the muscles closest to the center of the body. It causes weakness, inability to stand, climb stairs, lift, or reach. It may also cause muscle pain and difficulty swallowing, and may affect the lungs and heart. Having polymyositis increases the risk of certain types of cancer.

• Diseases characterized by inflammation involving multiple muscles. This may occur as an acute or chronic condition associated with medication toxicity drug toxicity); connective tissue diseases; infections; malignant neoplasms; and other disorders. The term polymyositis is frequently used to refer to a specific clinical entity characterized by subacute or slowly progressing symmetrical weakness primarily affecting the proximal limb and trunk muscles. The illness may occur at any age, but is most frequent in the fourth to sixth decade of life. Weakness of pharyngeal and laryngeal muscles, interstitial lung disease, and inflammation of the myocardium may also occur. Muscle biopsy reveals widespread destruction of segments of muscle fibers and an inflammatory cellular response. Adams et al., Principles of Neurology, 6th ed, pp1404-9)

• Inflammation of a number of voluntary muscles simultaneously.

Details

• M33.2 should not be used for reimbursement purposes as there are multiple codes below it that contain a greater level of detail.

• The 2023 edition of ICD-10-CM M33.2 became effective on October 1, 2022.

• This is the American ICD-10-CM version of M33.2 – other international versions of ICD-10 M33.2 may differ.