Mixed connective tissue disease

See also: Scleroderma

Now often called distinct rheumatologic disease, mixed connective tissue disease (MCTD) is variously considered an overlap (i.e., overlap connective tissue disease) between systemic lupus erythematosus (SLE), scleroderma, and polymyositis; a specific subset of scleroderma with objective features of other diseases, such as SLE or polymyositis; or a distinct disease entity. In Medical Subject Headings, it is termed "A syndrome with overlapping clinical features of systemic lupus erythematosus, scleroderma, polymyositis, and Raynaud's phenomenon. The disease is differentially characterized by high serum titers of antibodies to ribonuclease-sensitive extractable (saline soluble) nuclear antigen and a "speckled" epidermal nuclear staining pattern on direct immunofluorescence."

Most patients with MCTD have autoantibodies characteristic of scleroderma, such as U1 small nuclear ribonucleoproteins (anti-U1 snRNP OR anti-U1 RNP), and have clinical Raynaud's phenomenon.