Inclusion Bodies in the Gastric Muscularis Propria in Diabetic Gastroparesis: A Neglected Finding

Introduction: The histopathological features associated with various types of gastroparesis (GP) are still not well established. The most described cellular changes are decreased interstitial cells of Cajal (ICC), reduction in enteric nerves and abnormal immune infiltrates. There have been reports in the literature of inclusion bodies in the setting of multivisceral myopathy. Our aim was to determine if inclusion bodies could be detected in the gastric muscularis propria in gastroparesis patients and assess their possible clinical implications. Methods: Full thickness antral biopsies were obtained during surgery for placement of gastric electrical stimulator and performing pyloroplasty in 15 gastroparetic patients refractory to medical therapy (9 diabetic, 6 idiopathic) with mean age 38 ± 12 years. The biopsies were reviewed and stained by 1 pathologist (AT) with H&E, PAS, trichrome, S100 for glia, and c-Kit for interstitial cells of Cajal. Results: The inclusion bodies were identified in 3 of the 9 (33%) diabetic GP patients, all females aged 27, 37, and 57 years, but in none of the 6 idiopathic GP patients. The inclusion bodies histologically appeared as acellular eosinophilic inclusions in the smooth muscle and were associated with variable degrees of collagen fibrosis between the muscle bundles (Figure 1). Two of these 3 patients also showed reduced ICC (< 10HPF). None of these patients had abnormal neuronal inflammatory infiltrates.Figure 1: Inclusion bodies in muscularis layer.Conclusion: 1.) Inclusion bodies in the muscularis propria were identified in diabetic GP and absent in idiopathic GP patients, which may be considered as a distinguishing feature between these two types of GP. 2.) The presence of these inclusion bodies suggests that smooth muscle myopathy may be contributing to the GP in some diabetic patients. 3.) Further studies are needed to explore this histopathological finding and its clinical significance.