At the onset, many autoimmune connective tissue diseases (CTDs) are not fully evolved, and this early stage of the disease is known as undifferentiated connective tissue disease (UCTD). Approximately, 50% of cases of UCTDs remain undifferentiated throughout the disease course. All major CTDs have varying degrees of overlap in clinical features, and the degree of overlap correlates with their genetic and autoantibody profiles. Mixed connective tissue disease (MCTD) is a distinct prototype overlap syndrome with clinical features from lupus, rheumatoid arthritis, scleroderma, and myositis. Raynaud’s phenomenon is the most common presentation among patients with UCTD, overlap CTDs, and MCTD.