Overlap Syndromes in Autoimmune Connective Tissue Diseases

Abstract Autoimmune connective tissue diseases are a group of immune disorders, characterized by different clinical features, which affects not only the skin but also different organs and systems. Such diseases include: rheumatoid arthritis, systemic lupus erythematosus, Sjögren’s syndrome, systemic sclerosis, dermatomyositis and polymyositis. However, there are patients that fulfil the diagnostic criteria of more than one disorder, thus supporting the concept of the so called “overlap syndromes”. The aim of this review is to present the history, clinical and immunologic hallmarks of these overlap syndromes. Such conditions are scleromyositis, lupus erythematosus/lichen planus overlap, Sharp’s syndrome, Rhupus syndrome, Rowell’s syndrome, Reynolds syndrome and Senear-Usher syndromes. Patients with these syndromes usually do not meet most of the diagnostic criteria of “classic” connective tissue diseases and this usually causes diagnostic difficulties. Overlap syndromes are commonly treated with corticosteroids, hydroxychloroquine and immunosuppressant drugs as a first-line treatment. The new therapeutic molecules that precisely interact with immune mechanisms will require accurate diagnosis and a better understanding of the pathogenesis of the overlap syndromes.