If the neurologic examination is unrevealing, a more general physical examination, searching for extramuscular signs, is warranted ( Table 6 5 , 7 – 15 , 17 , 18 , 21 , 24 – 27 , 34 , 36 , 38 ) . Mental status testing may reveal changes suggestive of a myopathy-inducing electrolyte disorder (calcium or magnesium) or an arrest of mental development as occurs in genetic myopathies. 25 , 29 The cardiovascular assessment may elicit changes consistent with a cardiomyopathy—a nonspecific consequence of many myopathy-inducing disorders—or a pericarditis, as occurs with some of the infectious and rheumatologic causes of muscle weakness. 5 , 7 , 8 , 9 , 18 , 21 , 24 , 25 , 29 , 36 , 38
Polymyositis and the associated inflammatory myopathies have an associated increased risk of malignancy.  The features they found associated with an increased risk of cancer was older age, age greater than 45, male sex, dysphagia, cutaneous necrosis, cutaneous vasculitis, rapid onset of myositis (<4 weeks), elevated CK, higher ESR, higher CRP levels. Several factors were associated with lower-than-average risk, including the presence of ILD, arthritis/arthralgia, Raynaud's syndrome, or anti-Jo-1 antibody.  The malignancies that are associated are nasopharyngeal cancer, lung cancer, non-Hodgkin's lymphoma and bladder cancer amongst others. 
The muscle biopsy in AMC is diagnostic in the rare myopathies that cause AMC and in cases of denervation atrophy (provided an affected muscle is sampled). Denervation changes include classic individual or group myofiber atrophy. A significant proportion of biopsies show type 1 fiber predominance , which is probably the end result of denervation and collateral reinnervation. In the rest of AMC cases the muscle biopsy shows nonspecific findings such as myofiber atrophy and replacement of lost muscle with fibroadipose tissue. In some cases, muscle wastes so that only fibroadipose tissue remains. This probably gave rise to the notion of amyoplasia (., agenesis or absence of development of muscle). The term amyoplasia is used in literature to identify a clinical subset of AMC, not as a pathological diagnosis. There is no evidence of agenesis of muscle in AMC cases with detailed pathological studies.