M33.9

Clinical Information

• A subacute or chronic inflammatory disease of muscle and skin, marked by proximal muscle weakness and a characteristic skin rash. The illness occurs with approximately equal frequency in children and adults. The skin lesions usually take the form of a purplish rash or less often an exfoliative dermatitis) involving the nose, cheeks, forehead, upper trunk, and arms. The disease is associated with a complement mediated intramuscular microangiopathy, leading to loss of capillaries, muscle ischemia, muscle-fiber necrosis, and perifascicular atrophy. The childhood form of this disease tends to evolve into a systemic vasculitis. Dermatomyositis may occur in association with malignant neoplasms. from Adams et al., Principles of Neurology, 6th ed, pp1405-6)

• An inflammatory muscle disease accompanied by muscle weakness and skin rash

• Progressive condition characterized by symmetric proximal muscular weakness with elevated serum levels of muscle enzymes and a skin rash, typically a purplish-red erythema on the face, and edema of the eyelids and periorbital tissue; affected muscle tissue shows degeneration of fibers with a chronic inflammatory reaction; occurs in children and adults, and in the latter may be associated with visceral cancer or other disorders of connective tissue.

Details

• M33.9 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 M33.9 became effective on October 1, 2022.

• This is the American ICD-10-CM version of M33.9 – other international versions of ICD-10 M33.9 may differ.