Scleroderma Support Group
Scleroderma is a rare, chronic disease characterized by excessive deposits of collagen. Scleroderma affects the skin, and in more serious cases it can affect the blood vessels and internal organs. The most evident symptom is the hardening of the skin and associated scarring.
This explains that with MCTD you have an overlap of symptoms from some or all of the following: SLE (Lupus), Polymyositis and Scleroderma. Depending on which of the three your symptoms are most predominant in then you are labelled MCTD SLE like or whatever one it is.