Disaccharidase Deficiency Research Articles

Breath Testing in Intestinal Disaccharidase Deficiency and Bacterial Overgrowth of the Small Intestine

The breakdown and absorption of nutrients, a key function of the digestive system, is impaired in carbohydrate maldigestion and bacterial overgrowth of the small intestine. The resulting continuous irritation of the intestinal mucosa may have a systemic impact and lead to chronic conditions and increased susceptibility to parasitic infections. Precise diagnosis is therefore of great importance. Traditional methods are invasive, require large challenge doses or, as in elimination diets, do not provide definitive diagnosis. Measurement of hydrogen and methane levels in alveolar samples collected following a carbohydrate challenge is simple, non-invasive and provides good sensitivity and specificity. Breath tests can further definitively demonstrate lactose maldigestion, differentiate other carbohydrate intolerances and allow determination of severity of carbohydrate intolerance. Percentages of false-negatives and false-positives are low compared to traditional methods when instructions are followed properly. Technical advances in collection and analysis have greatly simplified breath tests. Advantages of breath testing for practitioners and patients make this a promising technique for future applications.

Regulation of Sucrase-Isomaltase Gene Expression in Human Intestinal Epithelial Cells by Inflammatory Cytokines

Using metabolic labeling techniques in human intestinal epithelial cell lines in tissue culture and in situ hybridization techniques in normal and inflamed (Crohn's) intestine, recent studies have shown that there is synthesis of acute phase proteins in enterocytes. Moreover, these studies have shown that acute phase protein biosynthesis in enterocytes is regulated by inflammatory cytokines in a manner characteristic of the physiologic acute phase response. In the course of these studies it was noticed that one inflammatory cytokine, interleukin-6 (IL-6), mediated selective down-regulation of the enterocyte-specific, differentiation-dependent integral membrane protein sucrase-isomaltase (SI) in the Caco2 intestinal epithelial cell line. In the current study we examined the effect of several other inflammatory cytokines interleukin-1 (IL-1 beta), tumor necrosis factor alpha (TNF alpha), and interferon gamma (IFN gamma) on synthesis of SI in Caco2 cells, examined the possibility that inflammatory cytokines affect the synthesis of other enterocyte integral membrane proteins using lactase as a prototype, and examined the possibility that SI gene expression was down-regulated in villous enterocytes in vivo during the local inflammatory response of Crohn's disease. The results show that IL-6 and IFN gamma each mediate a decrease and TNF alpha mediates an increase in synthesis of SI in Caco2 cells. The magnitude of down-regulation by IL-6 and IFN gamma is significantly greater than the up-regulation by TNF alpha. IL-1 beta has no effect on synthesis of SI. Synthesis of lactase is not affected by any of the cytokines. There is a marked specific decrease in SI gene expression in villous enterocytes in acutely inflamed Crohn's ileum as compared to adjacent uninflamed ileum and normal ileum. Taken together, these data show that inflammatory cytokines have specific and selective effects on the expression of the brush border hydrolase SI in tissue culture and in vivo and provide evidence for a previously unrecognized mechanism for disaccharidase deficiency in intestinal inflammation.

Purification of a fraction of Giardia lamblia trophozoite extract associated with disaccharidase deficiencies in immune Mongolian gerbils (Meriones unguiculatus).

The effects on disaccharidase activities of challenging gerbils previously exposed to Giardia lamblia with fradions of the crude trophozoite extract were examined. Gel filtration of the soluble extract on a Sephacryl S-200 HR column resulted in 3 fradions: F1, F2 and F3. Only a challenge with fraction F1 (0.1 mg total dose) was found to induce disaccharidase deficiencies. Boiling F1 prior to challenge did not change this effect on the enzyme activities. However, the decreases were not obtained when the total F1 dose was reduced to 0.05 mg. Column chromatography of fraction F1 under dissociating and reducing conditions resulted in 2 further fractions: F1a and F1b. Challenging immune gerbils with F1b led to impairments of disaccharidose activity similar to those obtained with F1. Protein analysis of the crude extract, as well as the fractions of the extract, revealed several high and low molecular weight bonds. These findings indicate that a constituent(s) of fraction F1b is the portion of the parasite which induces disaccharidase deficiencies in immune gerbils. This fraction consists of proteins ranging in molecular weight from 32 to 200 kDa. In addition the G. lamblia fraction involved in the decreases in enzyme activity is heat-stable.

FORMULA ALLERGY AND INTOLERANCE

There are two major types of adverse reactions in infant formulas: (1) formula allergy/hypersensitivity, which is an immunologic response, and (2) formula intolerance, which is a nonimmunologic response. Formula intolerance can occur in infants with an underlying congenital or acquired enzyme deficiency (disaccharidase deficiency, galactosemia, hereditary fructose intolerance). The clinical presentation, diagnosis, and treatment of both reactions are reviewed in this article. The appropriateness of the use of a variety of infant formulas is discussed. Guidelines for the prevention of allergic disease are described as well.

Disaccharidase activity in male and female C57BL/6 mice infected withGiardia muris

To elucidate the contribution of host and parasite factors in induction of small-intestinal disaccharidase deficiency in giardiasis, we determined the activity of four enzymes in male and female C57BL/6 mice infected with Giardia muris. Both male and female mice exhibited significant disaccharidase deficiency as shown by decreases in the activities of lactase, sucrase, trehalase and maltase on day 10 after infection. However, by 20 days after infection the females had normal enzyme activities, whereas those in males remained significantly reduced. Prolonged disaccharidase deficiency in the males was related to the course of the primary infection where males had higher parasite loads in the small intestine than did females on day 20 after infection. By day 40 after the primary infection the enzyme activities had returned to normal levels and were similar in male and female mice. Secondary exposure of mice to either the infective cysts or a crude extract of the trophozoites caused disaccharidase deficiency. The females had lower activities of sucrase and trehalase as compared with males after the challenge. Thus, during the primary infection, disaccharidase deficiency was strongly associated with parasite number, whereas after challenge infections the more resistant females had lower enzyme activities in the small intestine than did males.

Disaccharidase deficiencies in Mongolian gerbils (Meriones unguiculatus) protected against Giardia lamblia.

The activities of the disaccharidases lactase, maltase, sucrase and trehalase were examined in gerbils during Giardia lamblia infections. In a primary infection with trophozoites, the activities of all four enzymes were reduced from day 10 post-infection (p.i.) and remained at low levels well past the elimination phase of the infection. However, during a challenge infection, the disaccharidase decreases were short-lived, with impairments being seen only on days 2 and/or 4 post-challenge (p.c.). Sucrase activity was not affected by a challenge infection. When 0.1 mg of a soluble extract of G. lamblia trophozoites was used to challenge gerbils previously exposed to the live parasite, the pattern and duration of enzyme deficiencies were comparable with those observed after the challenge with the live parasite. In addition, decreasing the extract dose used to challenge the gerbils led to smaller disaccharidase deficiencies. G. lamblia-infected gerbils were also challenged with a soluble extract of Entamoeba histolytica trophozoites, and this had no effect on the disaccharidase activities. Therefore, the presence of the intact parasite was not necessary to induce enzyme reductions in immune animals. In addition, the effects seen during the secondary infection were parasite-specific and may have involved the host's immune response to Giardia antigens. Immune gerbils were further challenged with the in vitro-released excretory/secretory products of G. lamblia. Under our experimental conditions, disaccharidase activities were found to be affected by these products in a manner that was inconsistent with the results of the live parasite challenge, and this merits further study.

Morphological method for the diagnosis of human adult type hypolactasia.

The primary adult type hypolactasia is the most common form of genetically determined disaccharidase deficiency. This study examined a large and homogeneous population of the south of Italy: surgical biopsy specimens of proximal jejunum from 178 adult subjects have been assayed for disaccharidase activities; the expression of lactase protein and lactase activity has also been investigated on tissue sections by immunomorphological and enzymohistochemical techniques. Histograms of lactase to sucrase ratio were found to provide a useful distribution of the lactase activity; a lactase to sucrase ratio of 0.17 was found to show discrimination between tissues with persistence of high lactase activity and tissues with adult type hypolactasia. In all 28 subjects with persistent high lactase activity, a uniform distribution of lactase protein and lactase activity in all villus enterocytes was detected, whereas in all 150 subjects with adult type hypolactasia a variable number of villus enterocytes failed to express the lactase. Moreover in hypolactasic samples the lactase activity on tissue sections was constantly detected later than in samples with persistent high lactase activity. The absolute correlation between the immunohistochemical and enzymohistochemical features and the assessment of lactase activity in intestinal homogenates suggests that the morphological criteria are an alternative method for the diagnosis of adult type hypolactasia in human biopsy specimens from proximal small jejunum.

Small intestinal glucoamylase deficiency and starch malabsorption: A newly recognized alpha-glucosidase deficiency in children

To determine the prevalence of short polymers of glucose and starch malabsorption caused by small intestinal glucoamylase deficiency in children with chronic diarrhea, we studied small bowel biopsy specimens from 511 children (aged 1 month to 9 years) with chronic diarrhea evaluated at 54 medical centers. Glucoamylase and disaccharidase (lactase, sucrase, maltase, and palatinase) enzyme assays were performed. Of the 511 children, 15 had glucoamylase deficiency. Six who had significant small intestinal mucosal injury and disaccharidase deficiencies were defined as having secondary glucoamylase deficiency; the other nine patients with normal mucosal morphologic features were defined as having primary glucoamylase deficiency. Secretin tests showed normal pancreatic amylase values for age in all seven children tested. Four of them had abnormal findings on tolerance tests for starch and short polymers of glucose (rise in blood glucose concentration: < 20 mg/dl) and reducing substances in stools, and three of these four had symptoms of intolerance (abdominal distention, flatulence, and diarrhea). All seven patients responded to a starch elimination diet. After reintroduction of a starch diet, diarrhea recurred in four patients; this was alleviated 48 hours after reelimination of starch. We conclude that intestinal glucoamylase deficiency is present in some patients with chronic diarrhea.

COMMINUTED CHICKEN IN THE TREATMENT OF MALNOURISHED CHILDREN WITH PERSISTENT DIARRHEA

CREDES is a center for diagnosis and treatment of children with secondary malnutrition. Between January 1990 and June 1991, 21 infants (9.3% of all admissions) suffered from persistent diarrhea and of these, 19 did not respond to the initial dietary management. A locally made comminuted chicken formula (CCF) was assayed as an alternative to the expensive commercial formulae available for nutritional support. It consisted of 10% skinless chicken meat, 20-30% pureed carrots, 3-5% dextrinmaltose, 1-5% glucose and 3-5% vegetable oil. Of the children studied, 35% had birthweight under 2500g, 88% had been breastfed for a month or less and 50% had been hospitalized two or more times. On admission, patients had suffered as an average 13 morbid episodes. Mean W/A, H/A and W/H were 61.7%, 88.3% and 89.5% of the WHO/NCHS standards, respectively. Mean duration of hospitalization was 145.3 days (range 53-283). They were fed CCF for a mean of 145.3 days (59% of their hospitalization period) and they were regraded to a commercial formula before discharge. Restriction of sucrose intake associated to lactose withholding resulted in improvement of clinical symptomatology and of nutritional parameters. None of the patients required parenteral nutrition. The following diagnoses were made: celiac disease (4), cow's milk protein intolerance (2), agammaglobulinemia (1), secondary disaccharidase deficiencies (12, of which 5 were lactase and 10 sucrase deficiencies). On discharge W/A, H/A and W/H were 78.5%, 89.5% and 100,7%, respectively. CCF is a good alternative for the clinical management of these patients bacause of its acceptability, tolerance and low cost.

Disaccharidase activity in the small intestine of susceptible and resistant mice after primary and challenge infections with Giardia muris.

The activities of four disaccharidases were examined in resistant (C57Bl/6) and susceptible (C3H/HeN) mice during the primary infection with Giardia muris and after challenge with either trophozoite extract or cysts. Significant decreases in lactase, sucrase, trehalase, and maltase activities in C57Bl/6 mice and lactase and sucrase activities in C3H/HeN mice in the anterior 25% of the small intestine were observed on day 10 after infection. The activities of maltase, sucrase, trehalase, and lactase in the jejunum of C3H/HeN mice were significantly reduced after challenge with trophozoite extract, when compared with the uninfected or infected, but not challenged animals. Decreases in enzyme activities of C3H/HeN mice were evident as early as 12 hours after challenge with the extract. The resistant C57Bl/6 mice showed little change in disaccharidase activity after challenge with trophozoite extract. On the other hand, challenge with cysts resulted in a few decreases in disaccharidase activities in both strains of mice: C57Bl/6 mice showed decreases in the duodenum, while disaccharidases of C3H/HeN mice had lower activity more posteriorly. Thus, challenge with parasite antigen results in a more severe disaccharidase deficiency in susceptible hosts when compared with resistant ones.

Enzymes as agents for the treatment of disease

The replacement of genetically deficient enzymes in patients with inherited metabolic disorders by infusion of purified enzymes or by organ transplantation has had very limited success, although good results with bone marrow transplantation have been obtained in some patients with mucopolysaccharidosis, Gaucher disease and inherited immunodeficiency diseases. Genetic engineering of the patient's lymphocytes may ultimately render these approaches redundant, at least for some of these diseases. Treatment of chronic pancreatic insufficiency and of disaccharidase deficiency with oral enzymes can be very effective; therapy can be monitored in the latter by measuring the breath hydrogen excretion and in the former by a range of tests of which stool chymotrypsin assay is the most convenient. Treatment of acute myocardial infarction by intracoronary perfusion of thrombolytic enzymes can improve both cardiac function and long-term survival if given early enough. Successful reperfusion can be identified by changes in the kinetics of serum enzyme release and clearance, especially for the isoenzymes and isoforms of creatine kinase. In cancer chemotherapy, l-asparaginase has long been a useful adjunct in the treatment of acute lymphoblastic leukemia, but recent experience suggests a role in acute non-lymphoblastic leukemia as well.

Hepatic injury associated with small bowel bacterial overgrowth in rats is prevented by metronidazole and tetracycline

Susceptible rat strains develop hepatobiliary injury following the surgical creation of self-filling blind loops that cause small bowel bacterial overgrowth. Luminal bacteria or their cell wall polymers were implicated in the pathogenesis of the lesions because sham-operated rats and rats with self-emptying blind loops, having only slightly increased bacterial counts, did not develop hepatic injury. In this study, antibiotics with different spectra of activities were continuously administered starting 1 day or 22 days after surgery to determine which intestinal flora may be responsible for the development of hepatic injury in rats with small bowel bacterial overgrowth. Four weeks following surgery, Lewis rats with self-filling blind loops receiving no antibiotics had elevated liver histology scores (8.2 ± 1.3 vs. 0.7 ± 0.4) and plasma aspartate aminotransferase levels (269 ±171 vs. 84 ± 24) compared with sham-operated rats, P < 0.001. Oral gentamicin as well as oral and intraperitoneal polymyxin B, which binds endotoxin, did not prevent hepatic injury in rats with self-filling blind loops. However, oral metronidazole and tetracycline therapy continuously administered beginning 1 day after surgery diminished hepatic injury (histology score 3.0 ± 1.8, 2.9 ± 1.1; aspartate aminotransferase 87 ± 25, 98 ± 34; respectively P < 0.001 compared with self-filling blind loops receiving no antibiotics). Metronidazole also protected Wistar rats that require 12 weeks to develop hepatic injury following experimentally induced small bowel bacterial overgrowth compared with rats with self-filling blind loops that received no antibiotic treatment (histology score 10.4 ± 1.3 vs. 0.7 ± 1.1 and aspartate aminotransferase 273 ± 239 vs. 76 ± 20, P < 0.001). When rats started metronidazole therapy 22 days after self-filling blind loop surgery, elevated aspartate aminotransferase values decreased to normal during the next 77 days and final histology scores were normal. All rats with self-filling blind loops had negative peritoneal, liver, spleen, and blood cultures but approximately 75% of mesenteric lymph node cultures were positive irrespective of antibiotic treatment. Because Bacteroides species have been implicated in causing vitamin B12 and disaccharidase deficiencies in rats with self-filling blind loops, we documented the presence or absence of these organisms from blind loops using selective culture techniques. Metronidazole and tetracycline eliminated Bacteroides sp. from blind loops, but polymyxin B and gentamicin did not. These results suggest that Bacteroides sp. and possibly other anaerobic bacteria play an important role in the pathogenesis of hepatic injury associated with small bowel bacterial overgrowth.

Combined assessment of intestinal disaccharidases in congenital asucrasia by differential urinary disaccharide excretion.

Investigation of intestinal disaccharide hydrolysis and permeability by means of a non-invasive differential sugar absorption test was performed in a family containing two siblings with primary sucrase-isomaltase deficiency. The procedure, which depends on measurement of urinary excretion ratios after the oral administration of lactose, sucrose, palatinose, lactulose and L-rhamnose, is capable of simultaneous determination of intestinal lactase, sucrase, and isomaltase activity and lactulose:rhamnose permeability. The results corresponded well with those of disaccharidase assay and histological findings in jejunal biopsy tissue obtained from the patients. Palatinose proved a satisfactory substrate for in vivo assessment of intestinal isomaltase activity. The method described provides a reliable and comprehensive assessment of intestinal disaccharide hydrolysis, and simultaneous estimation of permeability assists discrimination of primary from secondary disaccharidase deficiency. The ability to assess three different disaccharidase activities in addition to intestinal permeability by means of a single test, and the simplicity of preservation and transport of urine samples for sugar analysis, makes this a convenient, definitive method for the investigation of defective sugar absorption in both patients and population groups.

Molecular aspects of disaccharidase deficiencies

We have described the methods used for studying the biosynthesis and the post-translational processing of sucrase-isomaltase (SI), lactase-phlorizin hydrolase (LPH) and maltase-glucoamylase (MGA) in human small intestinal mucosa. Our results are discussed in the context of findings by other researchers. A surprising finding coming out of all these studies is that SI, LPH and MGA are structurally quite different. SI and LPH are both synthesized as large molecular weight precursors which are proteolytically processed to the mature enzymes. In the case of SI, this processing occurs after insertion of the precursor into the brush border membrane and is catalysed by pancreatic proteases; the mature form consists of the two subunits sucrase and isomaltase, the latter containing an N-terminal peptide anchor. Proteolytic processing of the LPH-precursor occurs intracellularly, yielding a mature enzyme in the form of a two active site polypeptide which is anchored via a C-terminal peptide. The role of the large cleaved propolypeptide of LPH is not yet known. MGA is the largest of the three disaccharidases, having a molecular weight of > 300 kDa. No proteolytic processing seems to be taking place during biogenesis of MGA in human mucosa, and the mode of attachment to the membrane is unknown at present. The application of the methods described to the investigation of congenital sucrase-isomaltase deficiency (CSID) and lactase restriction in adults is presented and differences between CSID and LPH restriction are discussed.

Disaccharidase activity in the small intestine of gerbils (Meriones unguiculatus) during primary and challenge infections with Giardia lamblia.

The sequence of changes in the activity of six disaccharidases in the small intestine of gerbils during primary and secondary G lamblia infections was examined. The primary G lamblia infection induced a transient reduction in disaccharidase activity which was related to the highest trophozoite burden in the small intestine. During the primary exposure, a 30% to 85% decrease in the activity of enzymes was observed on days 10 and 20 after infection. Secondary exposure of gerbils to G lamblia caused a sharp decrease in disaccharidase activity as early as 24 h after challenge. The reduction in the enzyme activity was not influenced by the size of the challenge inoculum and occurred even when there were no live trophozoites in the small intestine. Disaccharidase deficiency could also be induced by challenge with the soluble extract of the trophozoites. Multiple challenge administrations of G lamblia trophozoites to gerbils induced a persistent disaccharidase deficiency. The results indicate that disaccharidase deficiency associated with the primary G lamblia infection probably represents a direct effect of the parasite on the brush border of the small intestine. On the other hand, the observed disaccharidase deficiency in the secondary G lamblia infection appears to be induced by the local immune responses of the host.

Small bowel biopsy for disaccharidase levels: evidence that endoscopic forceps biopsy can replace the Crosby capsule

Lactase, sucrase and maltase activities in endoscopic biopsies from the second part of the duodenum were compared to those in Crosby capsule biopsies from the proximal jejunum. In patients with villous atrophy disaccharidase activities were reduced compared with histologically normal mucosa in the duodenum and jejunum. Disaccharidase activities were significantly lower in the duodenum than in the proximal jejunum of patients with histologically normal mucosa and in those with partial villous atrophy but not significantly different for total villous atrophy patients. Primary and secondary disaccharidase deficiencies can be identified in biopsies from the duodenum. Duodenal biopsy is a valid alternative to jejunal biopsy for the diagnosis of disaccharidase deficiency.

Relationship of Endomysial Antibodies to Jejunal Mucosal Pathology

SummarySerum immunoglobulin A class antibodies reactive to the endomysial lining of the smooth muscle bundles of the gastrointestinal tract have recently been reported to be specific and sensitive indicators of celiac disease (CD). A total of 203 subjects were examined for serum endomysial antibodies (EmA) and in 103 small bowel biopsies were obtained. EmA were detected in 43 cases including 26 CD patients evaluated during the gluten challenge phase of diagnosis by European Society for Pediatric Gastroenterology and Nutrition criteria, 11 of 53 symptomatic patients, and 6 asymptomatic family members. All patients with detectable antibody at the time of biopsy exhibited grade III‐IV villous atrophy. Disaccharidase activities performed in 19 cases revealed severe deficiencies. EmA were not detected in 160 subjects including 42 infants and children with chronic nonspecific diarrhea. Eighteen of these possessed grade II‐III villous atrophy with moderate disaccharidase deficiency and 24 were found to have normal histology and enzymes. The EmA were also not detected in 3 CD patients who were well maintained on a gluten‐free diet for &gt; 1 year and 25 asymptomatic family members exhibiting normal histology and enzymes. An additional 90 infants and children with other gastrointestinal and liver diseases were also negative for the serum EmA. Fourteen of these patients underwent biopsies and were demonstrated to have normal histology.

Relationship of endomysial antibodies to jejunal mucosal pathology: specificity towards both symptomatic and asymptomatic celiacs.

Serum immunoglobulin A class antibodies reactive to the endomysial lining of the smooth muscle bundles of the gastrointestinal tract have recently been reported to be specific and sensitive indicators of celiac disease (CD). A total of 203 subjects were examined for serum endomysial antibodies (EmA) and in 103 small bowel biopsies were obtained. EmA were detected in 43 cases including 26 CD patients evaluated during the gluten challenge phase of diagnosis by European Society for Pediatric Gastroenterology and Nutrition criteria, 11 of 53 symptomatic patients, and 6 asymptomatic family members. All patients with detectable antibody at the time of biopsy exhibited grade III-IV villous atrophy. Disaccharidase activities performed in 19 cases revealed severe deficiencies. EmA were not detected in 160 subjects including 42 infants and children with chronic nonspecific diarrhea. Eighteen of these possessed grade II-III villous atrophy with moderate disaccharidase deficiency and 24 were found to have normal histology and enzymes. The EmA were also not detected in 3 CD patients who were well maintained on a gluten-free diet for greater than 1 year and 25 asymptomatic family members exhibiting normal histology and enzymes. An additional 90 infants and children with other gastrointestinal and liver diseases were also negative for the serum EmA. Fourteen of these patients underwent biopsies and were demonstrated to have normal histology.

Enzyme-substitution therapy with the yeast Saccharomyces cerevisiae in congenital sucrase-isomaltase deficiency.

Sucrase-isomaltase deficiency is an inherited disaccharidase deficiency that leads to malabsorption of sucrose, with resulting diarrhea and abdominal distention and cramps. We investigated the sucrose-splitting effect of viable yeast cells in eight children with congenital sucrase-isomaltase deficiency, by means of the sucrose hydrogen breath test. This test is based on the fact that hydrogen is released from the malabsorbed sucrose by the colonic microflora. We found that 0.3 g of lyophilized Saccharomyces cerevisiae, given after loading with 2 g of sucrose per kilogram of body weight, reduced hydrogen excretion in all patients, on average by 70 percent, in parallel with a complete loss or evident reduction of clinical symptoms. In vitro, lyophilized and fresh S. cerevisiae (fresh baker's yeast) had appreciable sucrase activity, a low isomaltase and maltase activity, and virtually no lactase activity. The sucrase activity was more inhibited by undiluted than by diluted gastric juice. We conclude that patients with congenital sucrase-isomaltase deficiency who intentionally or unintentionally consume sucrose can ameliorate the malabsorption by subsequently ingesting a small amount of viable yeast cells, preferably on a full stomach.

Effects of additional dietary gluten on the small-intestinal mucosa of volunteers and of patients with dermatitis herpetiformis.

In an attempt to confirm the existence of latent coeliac disease--dose-related gluten-sensitive enteropathy--we have increased dietary gluten by 20 g daily for 2 weeks, in 6 healthy adults and 11 patients with dermatitis herpetiformis (DH). Six of the DH patients had entirely normal jejunal morphology on a normal diet. Jejunal biopsy specimens were taken before and at the end of the study. Measurements of crypts, villi, and crypt mitoses were made on microdissected specimens; disaccharidases were assayed, and intraepithelial lymphocyte counts performed. In one of the six adult volunteers, gluten loading produced diarrhoea and jejunal biopsy abnormalities. Five DH patients on a gluten-free diet had deterioration of biopsy pathology after the gluten challenge. Features suggestive of a latent gluten-sensitive enteropathy were found in one of the other six DH patients; he developed disaccharidase deficiencies and villus atrophy when 20 g gluten was added to his usual gluten-containing diet. This study supports previous suggestions that a gluten-sensitive enteropathy may be latent and dose-related.