Alarcon-Segovia criterion (ASC) has been regularly used for diagnosing MCTD. Per ASC, to be diagnosed with MCTD, a patient should have a positive anti-U1-RNP antibody titer (>1:1600) as well as three out of the five following clinical features: Raynaud's phenomenon, hand swelling, sclerosis, synovitis, or myositis [2]. The gene discussed is U1; the disease is mixed connective tissue disease.