Is my polymyositis related to scleroderma?

Polymyositis: Polymyositis & scleroderma are both significant connective tissue disorders that both have autoimmune/ rheumatologic component. You need management by rheumatologist, at least to optimize the conditions.

Slight connection: Yes, they are both autoimmune diseases. However, they differ significantly in that polymyositis is an inflammatory disease of muscle and scleroderma is a tightening of the skin and sometimes the internal organs.

No: They are two distinct disease but both are autoimmune related with different mechanism. But it is possible to have both coexist as overlap syndrome. You will likely need in depth evaluation for diagnosis. Advise to see a rheumatologist.