Undifferentiated Connective Tissue Disease With Isolated Diaphragmatic Dysfunction.

Undifferentiated connective tissue disease (UCTD) is a rare autoimmune disorder with a prevalence of about two people per 100,000 people per year. Patients present with the features of different connective tissue diseases, including systemic lupus erythematosus, systemic sclerosis, polymyositis, and rheumatoid arthritis, with some positivity in serological markers that is insufficient to fulfill the criteria of any recognized connective tissue disorder. Pulmonary involvement is usually subacute and pleomorphic, which can cause a delay in the diagnosis. A few cases of UCTD involving an isolated diaphragm in the pulmonary system have been reported. We report a case of a 48-year-old female who initially presented with various nonspecific symptoms, including fatigue, polyarthralgia, dry mouth, and Raynaud's phenomenon. Subsequently, she developed significant dyspnea and orthopnea. Laboratory, immunology, and imaging workups were negative for any specific diagnosis. Pulmonary function tests showed severely low maximum inspiratory pressure (MEP) and maximum expiratory pressure, suggesting diaphragmatic dysfunction. A diagnosis of UCTD was considered, and she was treated with hydroxychloroquine and intravenous immunoglobulin (IVIG), which improved her respiratory symptoms and pulmonary function tests.