Background: Overlap syndrome is an entity that satisfies the criteria of at least two connective tissue diseases. These conditions include systemic sclerosis, dermatomyositis or polymyositis, Sjogren's syndrome, rheumatoid arthritis and systemic lupus erythematosus. A combined pathology has impact on the clinical features, diagnosis and treatment.

Objectives: To analyze the features of SSc[1] patients with overlap syndrome registered in the European (EUSTAR) database at our center and to review the literature focusing on clinical and diagnostic issues and new treatments.

Methods: We studied the medical records of 165 consecutive SSc patients and reviewed cases with scleroderma overlap syndrome. Using the key words “overlap syndrome," "systemic sclerosis," “connective tissue disease” and “biological agents” we conducted a PubMed search for the period 1977 to 2009.

Results: Forty patients satisfied the criteria for scleroderma overlap syndrome. The incidence of additional connective tissue diseases in the whole group and in the overlap syndrome group respectively was: dermatomyositis or polymyositis 11.5% and 47.5%, Sjogren's syndrome 10.3% and 42.5%, rheumatoid arthritis 3.6% and 15.4%, and systemic lupus erythematosus 1.2% and 5.0%. Coexistence of SSc and another CTD[2] aggravated the clinical course, especially lung, kidney, digestive, vascular and articular involvement. Non-rheumatic complications mimicked SSc complications. An additional rheumatic or non-rheumatic disease affected treatment choice.

Conclusions: The definition of scleroderma overlap syndrome is important, especially in patients who need high-dose corticosteroids for complications of a CTD. The use of novel biological therapies may be advocated in these patients to avoid the hazardous influences of high-dose steroids, especially renal crisis. In some overlap syndrome cases, biological agents serve both conditions; in others one of the conditions may limit their use. In the absence of formal clinical trials in these patients a cautious approach is preferred.