Brown bowel syndrome
Brown bowel syndrome is a rare condition characterized by a pathologic accumulation of lipofuscin predominantly within smooth muscle cells of the muscularis propria and to a lesser extent of the muscularis mucosae layers. It can rarely present in mesenteric lymph nodes within macrophages. It is PAS-positive and resistant to diastase digestion. It also stains with methylene blue, methenamine silver and Masson-Fontana.
Brown bowel syndrome is not a primary disease; it has been associated with severe malnutrition, especially vitamin E deficiency that often complicates chronic malabsorption syndromes caused by conditions such as celiac disease, pancreatic insufficiency or surgeries such as bariatric surgeries.
The pathogenesis of brown bowel syndrome is unclear. In the absence of vitamin E (antioxidant), oxidation of lipids, including the phospholipid layers of the mitochondrial membrane, occurs due to the presence of free oxygen radicals, resulting in aggregation of degraded mitochondrial membranes (lipofuscin) and mitochondrial dysfunction which in turn leads to atrophy and smooth muscle malfunction.
Brown bowel syndrome has been associated with toxic colonic dilatation, intestinal pseudoobstruction, intussusception and lower gastrointestinal bleeding.
Vitamin E deficiency can also result in the accumulation of dietary carcinogens. An association between small bowel carcinoma and brown bowel syndrome has been reported previously, however that connection is not clearly well-established.
Published reports suggest that treatment with long term vitamin E supplementation can improve the malabsorption symptoms and may decrease lipofuscin accumulation in the smooth muscle cells.
In conclusion, diseases that can cause severe malabsorption leading to fat soluble vitamin deficiencies can be associated with brown bowel syndrome that is associated with further disease symptoms and motility disorders. This association should be kept in mind in order to initiate the proper treatment and avoid further complications.
Contributed by Nour Yadak, MD and Michael Nalesnik, MD