Can mono cause shoulder and arm pain?

Unlikely: Shoulder and arm pain are not typical of mononucleosis. Mono is characterized by sore throat, fever, swollen neck lymph nodes, splenomegaly, abnormal liver enzymes, atypical lymphocytosis and a postitive mono serology.

Yes: Mono can mimic influenza symptoms: muscle & joint pains, loss of energy, sore throat, swollen glands, fever. Lyme disease & ehrlichiosis (from tick bites) can also cause such symptoms in joints. But r many other causes of musculoskeletal pain. See pcp for exam to determine cause & get treatment options.