2023 Mar 13. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–.
The connective tissues play a crucial role within organs by supporting and binding several types of tissues. If these tissues are targeted by the immune system, a connective tissue disease may occur, resulting in a wide range of signs and symptoms.
The connective tissue disease is an umbrella for a wide variety of diseases. For each one, there are diagnostic criteria. However, if the signs and symptoms of a patient do not meet any of these diagnostic criteria, the diagnosis of undifferentiated connective tissue disease will be established.
Undifferentiated connective tissue disease is a clinical entity defined as serological and clinical manifestations of systemic autoimmune disease. However, not fulfilling any criteria of defined connective tissue disease such as systemic lupus erythematosus, mixed connective tissue disease, Sjögren syndrome, systemic sclerosis, polymyositis, dermatomyositis, or rheumatoid arthritis. In clinical practice, the presence of undifferentiated connective tissue disease can be common.
The early phase of a major rheumatic disease was defined earlier by LeRoy et al. in 1980 as undifferentiated connective tissue disease in patients whose features did not meet other classification criteria.