Mixed connective tissue disease (MCTD), an autoimmune overlap condition characterized by high-titer anti-U1 ribonucleoprotein (U1 RNP) antibodies and clinical features resembling systemic lupus erythematosus, systemic sclerosis, and polymyositis, often presents with significant pulmonary involvement [1]. This evidence concerns the gene RNPC3 and mixed connective tissue disease.