The presence of mitochondrial abnormalities is now a criterion for the diagnosis of sporadic inclusion myositis. It is also a predictive marker of progression in other forms of inflammatory myopathies, according to a multicentre study involving researchers from the Institute of Myology (Paris):
- among 850 patients with myositis,
- 25 had COX-negative fibres (rate of 0.25 to 8.5%), without being affected by inclusion body myositis,
- they were distinguished by more frequent resistance to treatment and greater clinical severity,
- and even progression to inclusion body myositis in four out of 25 cases, after an initial diagnosis of polymyositis with mitochondrial pathology or non-specific myositis.
