Reader response: Granulomatosis-associated myositis: High prevalence of sporadic inclusion body myositis.

Abstract

We read with great interest the recent article by Dr. Dieudonne et al.1 The authors reported the high prevalence of sporadic inclusion body myositis (SIBM) in patients with granulomatous myositis, and a significant proportion of these SIBM patients also had systemic features suggestive of sarcoidosis. Their observation is similar to what we previously reported.2 In addition, we found that the majority of treatment-refractory granulomatous myositis patients had sarcoplasmic congophilic deposits, including those who did not fulfill the ENMC diagnostic criteria of SIBM. Although this was not statistically significant, the presence of congophilic aggregates—regardless of the diagnosis of SIBM—could be an indicator of treatment refractoriness. Dr. Dieudonne et al. analyzed the protein accumulation using TDP43 or p62 immunoreactivity, but we are not certain whether congo red stain was performed. We would appreciate if they can share their experience with congo red stain in their cohort because this is more widely available stain in routine clinical practice when compared with TDP43 and p62 immunostains. Last but not least, given the similar results of 2 relatively large cohorts of granulomatous myositis,1,2 an epidemiologic study looking into the incidence of SIBM in sarcoidosis could be of clinical interest.