Endocrine Abstracts

Introduction: Mixed connective tissue disease (MCTD), also known as Sharp´s syndrome is a rare autoimmune disease (AD), characterized by the presence of high titers of a distinctive autoantibody: ribonucleoprotein auto-antibody (anti-RNP). It presents with varied overlapping symptoms of different connective tissue disorders which may appear sequentially over time. As other AD, MCTD may be associated with one or more AD, such as autoimmune thyroid disorders (AITD).

Patients and methods: It is a descriptive retrospective single institution study. We collected data from 113 patients diagnosed with an AITD associated with another AD over 18 years. This present study reports the association between AITD and MCTD.

Results: We identified one patient diagnosed with both MCTD and AITD. She was hospitalized in the department of Internal medicine for investigation of joints pain and Raynaud’s phenomenon. Antibody testing showed positivity for anti-RNP. She was treated by a prescription of nonsteroidal anti-inflammatory drugs and calcium channel blockers. The evolution was marked by the occurrence of flares of arthralgias. Biochemical assays led to the fortuitous discovery of a hypothyroidism. Hashimoto’s thyroiditis (HT) was diagnosed concomitant to the MCTD in the context of other autoimmune diseases associated with the MCTD. Both thyroid antibodies (thyroid peroxydase antibody and thyroglobulin antibody) were positive. The patient was treated by L-thyroxin substitution.

Discussion and Conclusion: MCTD are AD characterized by the involvement of several organs and the presence of various autoantibodies. It can be associated with other AD. The most frequent association are with the Sjogrens’ syndrome, Hashimoto’s thyroiditis and some authors reported cases of autoimmune hepatitis and MCTD or primary biliary cirrhosis and MCTD. The frequency of thyroid disease, particularly chronic autoimmune thyroiditis (Hashimoto’s thyroiditis), may be increased in patients with MCTD and vice versa. In a study conducted by Biro et al. including 1517 patients bearing an AD, 159 patients were diagnosed with MCTD. Among them, 21.4% were also diagnosed with HT whereas only 2.5% were diagnosed with Graves’ disease. The screening of other autoimmune disorders in the presence of an AD is necessary, especially in patients who remain unwell or who develop new non-specific symptoms despite proper treatment, so as to avoid the delay in diagnosis of other autoimmune disorders and thus avoid treatment delay.

References: BiroE, Szekanecz Z, Czirjak L, Danko K, Kiss E, Szabo NA, et al. Association of systemic and thyroid autoimmune diseases. Clin Rheumatol. 2006; 25(2):240–5.