Background: Bohan and Peter criteria are widely used for the diagnosis of idiopathic inflammatory myopathies (IIMs). Recently, European Neuromuscular Center (ENMC) formulated criteria to identify subgroups of IIMs.
Aim: To compare the two diagnostic criteria in adult IIMs.
Materials and methods: This was a retrospective review of case records of histologically confirmed IIMs in adults between January 2014 and May 2015. Both the Bohan and Peter, and ENMC 2004 criteria were applied in the same group of patients to subgroup the IIMs. Muscle biopsy was evaluated in all the four domains: muscle fiber, inflammatory, connective tissue, and vascular, with the basic panel of histological stains. Sporadic inclusion body myositis (s-IBM) was diagnosed using ENMC IBM diagnostic research criteria 2011.
Results: During the study period, 69 patients fulfilled the ENMC criteria for IIMs including 16 patients with s-IBM. The subgrouping as per the ENMC criteria (53) was: dermatomyositis (DM) in 30; polymyositis (PM) in 2; immune-mediated necrotizing myopathy (IMNM) in 9; and nonspecific myositis (NM) in 12 patients, whereas subgrouping by the Bohan and Peter criteria was DM in 9 and PM with and without connective tissue disease (CTD) in 26 patients only. There was underdiagnosis of DM, as perifascicular atrophy is not recognized as a diagnostic histological feature, and overdiagnosis of PM with and without CTD due to poor characterization of histological features in PM by the Bohan and Peter criteria.
Conclusions: Systematic evaluation of muscle biopsy according to the ENMC criteria with basic panel of histochemical stains improved the diagnostic yield of IIM significantly when compared to the Bohan and Peter criteria.
Keywords: Bohan and Peter criteria; European Neuromuscular Center criteria; idiopathic inflammatory myopathies; muscle biopsy.