Other systemic involvement of connective tissue

M35.1 classifies other overlap syndromes, including mixed connective tissue disease (MCTD) — an autoimmune condition combining clinical features of systemic lupus erythematosus, systemic sclerosis, polymyositis, and Raynaud's phenomenon, typically confirmed by positive anti-U1 RNP antibodies.

M35.2 captures a confirmed diagnosis of Behçet's disease, a rare systemic autoinflammatory vasculitis characterized by recurrent oral and genital ulcers, uveitis, and variable involvement of the joints, skin, nervous system, and gastrointestinal tract.

Polymyalgia rheumatica (PMR) — a systemic inflammatory syndrome of older adults producing proximal bilateral pain and stiffness in the shoulder and hip girdles, typically accompanied by elevated inflammatory markers.

M35.4 identifies diffuse (eosinophilic) fasciitis, a rare systemic fibrosing disorder characterized by inflammatory thickening of the deep fascia with associated peripheral eosinophilia, classified under other systemic involvement of connective tissue.

M35.5 identifies multifocal fibrosclerosis — a rare systemic connective tissue disorder characterized by fibrotic proliferation at multiple anatomic sites simultaneously, classified under Other Systemic Involvement of Connective Tissue (M35).

M35.6 classifies relapsing panniculitis of the Weber-Christian type — a systemic connective tissue disorder characterized by recurring episodes of inflammation in subcutaneous and, in some cases, visceral adipose tissue, presenting with painful nodules, erythema, fever, and myalgia.

M35.7 classifies hypermobility syndrome — a connective tissue condition characterized by excessive joint laxity beyond normal range, often associated with chronic pain, recurrent subluxations, and generalized ligamentous laxity including familial ligamentous laxity.

M35.9 captures systemic connective tissue involvement when the clinical picture does not meet criteria for — or cannot yet be differentiated into — a named disorder such as lupus, scleroderma, Sjögren syndrome, or mixed connective tissue disease. Applicable-To notes include 'Autoimmune disease (systemic) NOS' and 'Collagen (vascular) disease NOS.'