Microscopic (collagenous and lymphocytic) colitis triggered by food allergy

Collagenous and lymphocytic colitis^1,2 are rare³ diseases of unknown aetiology but several issues,^1–3,5 in particular the good response to budesonide,⁷ are suggestive of immunopathology. Patients have watery diarrhoea without abnormal findings on colonoscopy^1–5 but with increased numbers of intraepithelial lymphocytes, mast cells, and eosinophils⁵ on histological examination.

We report six patients seen between 1993 and 1999 who were first diagnosed as having collagenous/lymphocytic colitis. Signs of allergy entailed a work up for food allergy. (table 1 ▶)

Table 1.

 Patient characteristics

Sex	Age (y)	Follow up (y)	Atopy	Signs of allergy	Diagnostic markers suggestive of allergy	Identified allergen
F	49	5	+	Improvement by hypoallergenic diet	Eos in bx	Egg, pollen, housedust mite
M	45	5	−	Urticaria, improvement by cromolyn	UMH	—
M	46	5	−	Pansinusitis	Eos in bx	Spices, moulds, flours, celery, nuts, milk, maize, rice, apple, celery, soy
M	52	3	−	IgG deficiency	Eos in bx	Maize starch
M	71	9	+	Prick	Prick, RAST	Milk, egg, soy
F	59	4	+	Prick	UMH	Ananas

Eos in bx, eosinophils in colon biopsy; UMH, urine methylhistamine.

All patients were investigated with skin prick testing, total and allergen specific IgE with food, and environmental allergens. Excretion of urine methylhistamine (UMH) was measured⁸ on a normal and hypoallergenic potato-rice diet. Colonoscopy with endoscopically guided segmental lavage for intestinal IgE was carried out⁹ and biopsies were investigated by routine pathology (haematoxylin-eosin), immunohistochemistry for eosinophil peroxidase, and amount of eosinophil cationic protein and tryptase⁹ in the whole biopsy. Clinical activity was mainly assessed by number of stools/day⁷ and the Karnofsky index for general performance.

After allergen identification, all patients were counselled on elimination of the allergen, except for one case where no allergen was identified. In this case, in a second patient with multiple sensitisations, and in a third with allergy to basal foods, additional cromolyn therapy was initiated. A trial of hypoallergenic diet and subsequent controlled addition of food with low allergenicity was performed. Additional antihistaminergic therapy (fexofenadine) was recommended as supplementary therapy for periods of exacerbation.

All patients were followed prospectively every 12 months after diagnosis (outpatient clinic and structured telephone interview) and all had symptom reduction in terms of stool frequency and consistency (table 2 ▶). General performance was completely restored in four patients and improved in one. The remaining patient is still very restricted in his activities due to incapacitating coronary artery disease but his gastrointestinal symptoms are tolerable.

Table 2.

 Number of stools per day (Baerts score⁷)before and after therapy

Sex	Age (y)	Before diagnosis	After diagnosis
F	49	5–10	1–2
M	45	5	0
M	46	4–6	0–1
M	52	10	1
M	71	4	1
F	59	5	1

Another patient was not willing to undergo colonoscopy for lavage and allergen identification, nor willing to quit smoking. His stools normalised after a six month course of cromolyn but he still suffers from bouts of diarrhoea during stress. He considers his general performance as good.

Histology was available for one patient before and after therapy. After dietary elimination, eosinophilic infiltrate was markedly less dense and degranulated.

The mechanisms of diarrhoea in collagenous colitis include a pronounced diffusion barrier with diminished net absorption of sodium and chloride ions.⁶ Allergens could induce increased eosinophil infiltration and enhance transforming growth factor β¹⁰ with increased collagen deposition. Eosinophils are highly susceptible to steroids which may explain the good response of collagenous colitis to budesonide.⁴

In summary, a subgroup of patients with microscopic colitis suffer from food allergy. Further work up for allergy is sensible in those patients with a history of atopic disease or blood/tissue eosinophilia. Allergen elimination can decrease or abolish the need for medication. Antiallergic therapy can be added to the therapeutic regimen.