Eosinophilic colitis is a controversial diagnosis. It can occur secondary to a number of conditions, including worm infestation and medical reactions, but cases without a primary cause have been reported less than 100 times in literature.
Eosinophilic colitis patients often have generic lower GI symptoms, including abdominal pain, constipation, diarrhea, and rectal bleeding. More severe cases can cause malabsorption, protein losing enteropathy, colonic wall thickening, obstructive features, eosinophilic ascites and weight loss. Unusually, these symptoms have a relapsing-remitting course, with sudden, inexplicable remission from symptoms. Eosinophilic colitis affecting infants has been segregated into its own diagnoses, which are allergic proctocolitis and FPIES. These are both due to allergic reactions from food proteins.
Eosinophilic colitis most often affects otherwise healthy infants or young adults, in whom it is more often chronic. The only defined feature is a dense eosinophilic infiltration in the colon. Infiltration can be contiguous or diffuse. Endoscopy reveals edema and patchy granularity. Crypt abscesses and lymphonodular hyperplasia may be present.
One study on typical eosinophil values in patients without history of GI issues found that there was a mean eosinophil count of 17/hpf. However, the range of cell count was wide, from 1-52. 28% of biopsies averaged more than 20 eosinophils/hpf. A mean of 35/hpf was found in the cecum, with a mean of 10/hpf in the rectum. Another study found 5-35 eosinophils/hpf in the colon, with count decreasing closer to the rectum. A diagnostic marker of greater than 60 eosinophils/ 10 hpf has been suggested for eosinophilic colitis. Others have used greater than 30/hpf.
Eosinophilic colitis patients sometimes have peripheral eosinophilia and are more likely to have an elevated total serum IgE level. Some patients with eosinophilic colitis have self reported other types of EGID, but there is not yet a biopsy proven link. Interestingly, eosinophilic colitis is not related to a history of atopy. It has been linked to scleroderma and liver transplantation in children. Two cases of eosinophilic colitis have occurred in children with autism. Eosinophilic colitis is thought to occur via a CD4+ Th2 lymphocyte mediated mechanism rather than an IgE mediated mechanism.
Due to its rarity, eosinophilic colitis has not been well researched and is not well understood. In particular, the relapsing-remitting course is baffling. It is worthwhile to note that eosinophils are seen readily using the standard H&E stain employed as a first measure in hospital labs, so they are unlikely to go unseen like mast cells. Some doctors believe it presents as a part of a larger syndrome that is sometimes missed when evaluating patients.
Treatment is much the same as other eosinophilic GI diseases. Elimination dieting is strongly recommended. Corticosteroids, such as budesonide, are often employed. Azathioprine is sometimes used. Ketotifen may be used in place of steroids.
References:
Alfadda, Abdulrahman A., et al. Eosinophilic colitis: epidemiology, clinical features, and current management. Ther Adv Gastroenterol (2010) 4(5): 301-309.
Gonsalves, N. Food allergies and eosinophilic gastrointestinal illness. Gastroenterol Clin North Am 36: 75-91, vi.