Risk Factors for Idiopathic Inflammatory Myopathies

There are no risk factors as such, but the association between muscular diseases and cancer is unquestionable, with cases having been described as long as 100 years ago, although it was not until 1990 that the association between dermatomyositis and polymyositis and cancer was definitively confirmed in adults.

For inclusion body myositis (IBM) there is no evidence of an increased cancer risk compared to the general population; in contrast, for dermatomyositis and polymyositis the risk of cancer is clearly higher, especially for dermatomyositis. The probability of developing cancer is three times higher in women and twice as high in men who suffer dermatomyositis.

Although the evidence collected to date suggests that both immune-mediated necrotising myopathy (IMNM) and antisynthetase syndrome (AS) may also be linked to cancer, the absence of large population-based studies makes it difficult to draw any firm conclusions.