Which connective tissue disorder is characterized by insoluble collagen being formed and accumulating excessively in the tissues?

Answer; 
Scleroderma

Scleroderma is a connective tissue disorder that is characterized by insoluble collagen being formed and accumulating excessively in the tissues. 

Explanation; 
This disorder features thickened skin that can involve scarring, blood vessel problems, varying degrees of inflammation and pain, and is normally associated with an overactive immune system. It is regarded as an autoimmune condition, as the body produces too much collagen, causing the skin and connective tissue to thicken.