# A Case of Overlapping Autoimmune Syndrome

## TL;DR

A rare case of overlapping autoimmune diseases in a patient with mixed connective tissue disease and anti-synthetase syndrome is reported, highlighting the importance of early diagnosis and tailored treatment.

## Contribution

The paper presents a unique case of overlapping autoimmune conditions with distinct antibody profiles and treatment response.

## Key findings

- A 44-year-old female showed features of both MCTD and ASS with initial antibody positivity.
- Treatment with corticosteroids and mycophenolate mofetil led to temporary breathing improvement.
- After treatment completion, the patient was anti-Jo-1 negative and anti-CCP positive.

## Abstract

Overlapping autoimmune disorders are used to describe the coexistence of more than one autoimmune disease in the same patient. Mixed connective tissue disease (MCTD) and anti-synthetase syndrome (ASS) are autoimmune diseases that manifest with pulmonary involvement, presenting as persistent dyspnea. The coexistence of both conditions in the same patient is extremely rare. We herein report a case of a 44-year-old female who was diagnosed with MCTD with features of ASS (anti-Jo-1 antibody) in the setting of rheumatoid arthritis (anti-cyclic citrullinated peptide (anti-CCP) antibody), which shows temporary breathing improvement following treatment with corticosteroid and mycophenolate mofetil. However, after the completion of mycophenolate mofetil, she was found to be anti-Jo-1 antibody negative and anti-CCP antibody positive. Our case emphasizes the need to recognize overlapping autoimmune conditions in patients with complex clinical features and presentations with the immediate application of a comprehensive diagnostic approach and tailored treatment strategies. Early diagnosis and aggressive treatment are crucial for achieving remission and preventing organ damage.