[Is mixed connective tissue disease a distinct rheumatic disease]

Area of Science:

• Rheumatology
• Immunology
• Genetics

Background:

• The classification of Mixed Connective Tissue Disease (MCTD) as a distinct clinical entity remains debated.
• Understanding MCTD's distinctiveness is crucial for accurate diagnosis and patient management.

Purpose of the Study:

• To evaluate the reliability of diagnostic criteria for MCTD.
• To investigate the clinical evolution of patients diagnosed with MCTD.
• To explore the association of HLA antigens with MCTD diagnosis.

Main Methods:

• Longitudinal observation of 50 patients diagnosed with MCTD.
• Evaluation of diagnostic criteria by Sharp, Alarcon-Segovia, and Kasukawa.
• HLA-A, -B, and -DR antigen typing in 38 patients.

Main Results:

• 13% of MCTD patients developed other connective tissue diseases (CTDs).
• Sharp's criteria showed higher reliability in diagnosing MCTD, with fewer patients progressing to other CTDs compared to Kasukawa's and Alarcon-Segovia's criteria.
• Significant differences in HLA-DR and HLA-DR5 frequencies were observed in patients meeting Sharp's criteria compared to controls.

Conclusions:

• Mixed Connective Tissue Disease (MCTD) is a distinct rheumatic disease.
• Sharp's diagnostic criteria are the most reliable for identifying MCTD.
• HLA antigen profiles may aid in MCTD diagnosis.