The term overlap syndromes (OS) is used to define a group of disorders characterized by the presence, in the same patient, of clinical features typical for more than one definite connective tissue disease (CTD).
Objective: To show that patients may not only have an overlap of two or more CTDs but may also change their disease phenotype from that of a definite CTD to another.
Patients and methods: Retrospective analysis of medical records of four patients with a disease duration of about thirty years and a transition from a well definite CTD into another.
Results: The first patient was diagnosed, at the beginning of the 1980s, as affected by diffuse cutaneous systemic sclerosis (dcSSc) and developed systemic lupus erythematosus (SLE) twenty-five years later. The second and the third patients were diagnosed with SLE at the beginning of their disease: the second patient developed, in the course of her disease, an overlap syndrome (OS) SSc/rheumatoid arthritis (RA) and the third SSc and finally microscopic polyangiitis (MPA). The fourth patient was diagnosed as primary Sjogren’s syndrome (SS) then as rheumatoid arthritis (RA) and finally developed SLE.
Conclusions: Patients may not only show an overlap of two or more CTDs but also a transition from a well definite CTD into another. We propose the term “transitional connective tissue diseases” (TCTDs) to define their disease. A higher number of patients may allow us to better identify this new subgroup of CTDs and probably, also, predictors of evolution.