The molecular basis of intractable diarrhoea of infancy

Congenital enteropathies involving defects in enterocyte structure or differentiation

Congenital enteropathies (CE) are a group of rare inherited diseases with a typical onset early in life. They involve defects in enterocyte structure or differentiation. They can cause a severe condition of intestinal failure (IF). The diagnostic approach is based first on clinical presentation (consanguinity, prenatal expression, polyhydramnios, early neonatal onset, aspect of stools, persistence at bowel rest, associated extra-digestive manifestations….) and histo-pathological analyses. These rare intestinal diseases cause protracted diarrhea that might resolve, for a few, with a dietetic approach. However, protracted or permanent IF may require long term parenteral nutrition and, in limited cases, intestinal transplantation. With the progresses in both clinical nutrition and genetics, many of these CE are nowadays associated with recognized gene mutations. It improved our knowledge and the understanding in the patho-physiology of these diseases, thus, leading potentially to therapeutic perspectives. These review cover most of the early onset CE and excludes the immune related diarrhea.

Immune dysregulation, polyendocrinopathy, enteropathy, x-linked syndrome: a paradigm of immunodeficiency with autoimmunity

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare monogenic primary immunodeficiency (PID) due to mutations of FOXP3, a key transcription factor for naturally occurring (n) regulatory T (Treg) cells. The dysfunction of Treg cells is the main pathogenic event leading to the multi-organ autoimmunity that characterizes IPEX syndrome, a paradigm of genetically determined PID with autoimmunity. IPEX has a severe early onset and can become rapidly fatal within the first year of life regardless of the type and site of the mutation. The initial presenting symptoms are severe enteritis and/or type-1 diabetes mellitus, alone or in combination with eczema and elevated serum IgE. Other autoimmune symptoms, such as hypothyroidism, cytopenia, hepatitis, nephropathy, arthritis, and alopecia can develop in patients who survive the initial acute phase. The current therapeutic options for IPEX patients are limited. Supportive and replacement therapies combined with pharmacological immunosuppression are required to control symptoms at onset. However, these procedures can allow only a reduction of the clinical manifestations without a permanent control of the disease. The only known effective cure for IPEX syndrome is hematopoietic stem cell transplantation, but it is always limited by the availability of a suitable donor and the lack of specific guidelines for bone marrow transplant in the context of this disease. This review aims to summarize the clinical histories and genomic mutations of the IPEX patients described in the literature to date. We will focus on the clinical and immunological features that allow differential diagnosis of IPEX syndrome and distinguish it from other PID with autoimmunity. The efficacy of the current therapies will be reviewed, and possible innovative approaches, based on the latest highlights of the pathogenesis to treat this severe primary autoimmune disease of childhood, will be discussed.

Enteropathies of Infancy and Childhood

Intestinal biopsies constitute an ever-increasing portion of the pathologist's workload, accounting for nearly two-thirds of specimens accessioned yearly by the pathology department at The Children's Hospital of Philadelphia. The widespread use of endoscopy and gastrointestinal biopsies in current clinical practice presents the pathologist with a diversity of intestinal mucosal appearances corresponding to disease states of variable clinical severity, requiring close collaboration between clinician and pathologist for optimal interpretation. Many of the entities resulting in severe diarrhea of infancy have been recognized only in the last several decades, and although rare, the study of these disorders, especially when combined with the powerful methods of present-day genetics and molecular biology, has afforded important insights into enterocyte development and function, and intestinal immunity and tolerance. Other conditions once considered infrequent, such as celiac disease, have now been recognized to be much more common and can present with a wide range of pathologic features.

Clinics of coeliac disease in children in the 2000s

OBJECTIVE

To describe the clinical picture of patients with coeliac disease (CD) and the change in its presentation over the past decades.

STUDY DESIGN

Patients with CD were identified and clinical data collected from hospital records over a 6-year period (2000-2005).

RESULTS

Altogether 197 patients aged 0.6-15.9 (mean 7.2) years were identified. They were found amongst the child population served by the hospital, the mean number of children at age 0.5-16 years was 268 000 during 2000-2005. The presenting symptom amongst the youngest patients (<3 years) was chronic diarrhoea (in 67%), and amongst older patients, abdominal pain. At the time of diagnosis, growth was severely retarded (height <2 SD for age) in 6.6%; mean height was -0.06 SD and weight + 1% for height. After diet treatment for a mean of 6 months, both height and weight increased significantly. Anaemia and iron deficiency were present in 25% and 43% of patients respectively. Intraepithelial T-cell receptor gamma/delta cells were pathologic in all 150 specimens studied.

CONCLUSIONS

The presentation of CD depends on age. Even when we found six times more patients than during years 1976-1985 in the same hospital, published data on the prevalence of CD suggest that we found only a small minority of children with CD.

Syndromic (phenotypic) diarrhea in early infancy

Syndromic diarrhea (SD), also known as phenotypic diarrhea (PD) or tricho-hepato-enteric syndrome (THE), is a congenital enteropathy presenting with early-onset of severe diarrhea requiring parenteral nutrition (PN). To date, no epidemiological data are available. The estimated prevalence is approximately 1/300,000–400,000 live births in Western Europe. Ethnic origin does not appear to be associated with SD. Infants are born small for gestational age and present with facial dysmorphism including prominent forehead and cheeks, broad nasal root and hypertelorism. Hairs are woolly, easily removed and poorly pigmented. Severe and persistent diarrhea starts within the first 6 months of life (≤ 1 month in most cases) and is accompanied by severe malabsorption leading to early and relentless protein energy malnutrition with failure to thrive. Liver disease affects about half of patients with extensive fibrosis or cirrhosis. There is currently no specific biochemical profile, though a functional T-cell immune deficiency with defective antibody production was reported. Microscopic analysis of the hair show twisted hair (pili torti), aniso- and poilkilotrichosis, and trichorrhexis nodosa. Histopathological analysis of small intestine biopsy shows non-specific villous atrophy with low or no mononuclear cell infiltration of the lamina propria, and no specific histological abnormalities involving the epithelium. The etiology remains unknown. The frequent association of the disorder with parental consanguinity and/or affected siblings suggests a genetic origin with an autosomal recessive mode of transmission. Early management consists of total PN. Some infants have a rather milder phenotype with partial PN dependency or require only enteral feeding. Prognosis of this syndrome is poor, but most patients now survive, and about half of the patients may be weaned from PN at adolescence, but experience failure to thrive and final short stature.

Syndromic diarrhea – Phenotypic diarrhea – Tricho-hepato-enteric syndrome – Intractable diarrhea of infancy with facial dysmorphism – Trichorrhexis nodosa and cirrhosis – Neonatal hemochromatosis phenotype with intractable diarrhea and hair abnormalities – Intractable infant diarrhea associated with phenotypic abnormalities and immune deficiency.

Gluten sensitive enteropathy and other causes of small intestinal lymphocytosis

Recent studies on gluten sensitive enteropathy (GSE) have heightened the pathologist's awareness of intraepithelial lymphocytes in duodenal biopsies. Mild histologic forms of GSE are now recognized with increased IELs as the only histologic change. In this review, both the classic morphology and "minimal deviation" GSE are discussed in detail, with special emphasis on the differential diagnosis and how to avoid overdiagnosing this condition. The Marsh-Oberhuber classification is described and contrasted with a more practical diagnostic terminology that is recommended for use in pathology reports. Other important conditions associated with duodenal lymphocytosis, such as refractory sprue, autoimmune enteropathy, and Helicobacter pylori-associated duodenitis, are also presented.

Chronic T cell-mediated enteropathy in rural west African children: relationship with nutritional status and small bowel function

Previous studies from The Gambia have shown that poor childhood growth is resistant to all but the most intense nutritional intervention and highly dependent on small bowel permeability related to enteropathy. We thus aimed to characterize the mucosal inflammatory response in rural Gambian children in relation to intestinal permeability and nutritional status. Small bowel biopsies were taken from 38 rural Gambian children (age, 0.5-3 y) with a range of nutritional and clinical states (median weight z score, -4.6; range, 0.5 to -6.4), 75% of whom had diarrhea. Morphometry was performed with immunohistochemical analysis for a range of lineage and activation markers, including proinflammatory and regulatory cytokines, and related to current clinical status and gut permeability. Comparison was made with 19 age-matched U.K. controls. All Gambian children, regardless of nutritional status, had evidence of chronic cell-mediated enteropathy with crypt hyperplasia, villous stunting, and high numbers of intraepithelial lymphocytes. CD25+ cells were 20-fold higher than in U.K. controls. Although small bowel architecture was independent of nutritional status, T cell numbers rose and B cell numbers fell with worsening nutrition, and mucosal cytokine production became biased toward a proinflammatory response, with progressive decrease of transforming growth factor-beta expression. Tropical enteropathy predates the onset of marasmus and is characterized by a cell-mediated TH1 response. Protein-energy malnutrition is associated with reduction of regulatory immune responses in the mucosal microenvironment, potentially impairing the mechanisms of oral tolerance.

Natural history of intestinal failure, investigated through a national network-based approach

OBJECTIVES

Intestinal failure (IF) is a condition whose treatment requires advanced knowledge and techniques and a multidisciplinary approach. Intestinal failure is the endpoint of many intestinal diseases and may result in full recovery, in life-long parenteral nutrition, or in the death of the child. The aim of this study was to evaluate the natural history of IF in children using a national network of resources.

METHODS

Italian centers of pediatric gastroenterology merged in a national network, developing a collaborative management approach for children with IF. A consensus definition of IF was achieved. A database was set up to investigate the cause, epidemiologic factors, and natural history of IF.

RESULTS

One hundred nine children were enrolled in 5 years. The cause of IF was: short bowel syndrome (n = 48), disorders of motility (n = 16), structural enterocyte defects (n = 14), multiple food intolerance (n = 10), autoimmune enteropathy (n = 7), and others or unknown (n = 14). The eventual outcome was closely related to the primary cause, ranging from full and permanent intestinal sufficiency in children with multiple food intolerance to high death rate or total dependance upon parenteral nutrition in those with structural enterocyte defects. Intermediate outcomes were observed for the other causes. Four children received intestinal transplantation.

CONCLUSIONS

The network approach for IF provides an effective model to optimize resources and to investigate prospectively the natural history of IF. Based on the work on this series, a European network for IF could be an effective model for fulfilling the diagnostic and management needs, including intestinal transplantation.

Reduced heparan sulfate accumulation in enterocytes contributes to protein-losing enteropathy in a congenital disorder of glycosylation

Intestinal biopsy in a boy with gastroenteritis-induced protein-losing enteropathy (PLE) showed loss of heparan sulfate (HS) and syndecan-1 core protein from the basolateral surface of the enterocytes, which improved after PLE subsided. Isoelectric focusing analysis of serum transferrin indicated a congenital disorder of glycosylation (CDG) and subsequent analysis showed three point mutations in the ALG6 gene encoding an alpha1,3-glucosyltransferase needed for the addition of the first glucose to the dolichol-linked oligosaccharide. The maternal mutation, C998T, causing an A333V substitution, has been shown to cause CDG-Ic, whereas the two paternal mutations, T391C (Y131H) and C924A (S308R) have not previously been reported. The mutations were tested for their ability to rescue faulty N:-linked glycosylation of carboxypeptidase Y in an ALG6-deficient Saccharomyces cerevisiae strain. Normal human ALG6 rescues glycosylation and A333V partially rescues, whereas the combined paternal mutations (Y131H and S308R) are ineffective. Underglycosylation resulting from each of these mutations is much more severe in rapidly dividing yeast. Similarly, incomplete protein glycosylation in the patient is most severe in rapidly dividing enterocytes during gastroenteritis-induced stress. Incomplete N:-linked glycosylation of an HS core protein and/or other biosynthetic enzymes may explain the selective localized loss of HS and PLE.

Severe and protracted diarrhea: results of the 3-year SIGEP multicenter survey. Working Group of the Italian Society of Pediatric Gastroenterology and Hepatology (SIGEP)

BACKGROUND

The spectrum of severe and protracted diarrhea (SPD), previously defined as intractable diarrhea, has changed during the past several decades. Despite recent advances in determining the cause of SPD and in treatment, this syndrome still represents a challenge and is becoming a major problem affecting health care resources. This study was conducted to characterize the epidemiology, spectrum of causes, and the outcome of SPD in Italy in recent years.

METHODS

All the SPD cases seen at the major centers of pediatric gastroenterology in Italy during a 3-year period (1993-1996) were recruited in this multicenter, prospective survey.

RESULTS

Thirty-two children (26 boys and 6 girls; median age at the onset of SPD, 40 days) were enrolled in this study by 9 of 26 participating centers. Twelve were newly diagnosed cases, with an estimated SPD incidence rate in Italy of 0.64 to 0.92 x 10(-5) infants per year. The most common causes were autoimmune enteropathy (n = 8) and ultrastructural abnormalities of the enterocyte (n = 7), whereas food intolerance and postenteritis syndrome were less frequent (3 and 2 cases, respectively). Two children with autoimmune enteropathy fulfilled the criteria for the X-linked variant of this condition. At the end of the study period, 9 of 31 patients had recovered, 15 still had diarrhea, and 7 had died.

CONCLUSIONS

Severe and protracted diarrhea is a rare but challenging problem in Italy. Because parenteral nutrition or intestinal transplantation are the only options in a subset of cases (e.g., ultrastructural abnormalities of the enterocyte), infants with SPD should be referred to specialized centers where advanced diagnostic and therapeutic facilities are available.

Autoimmune enteropathy with distinct mucosal features in T-cell activation deficiency: the contribution of T cells to the mucosal lesion

BACKGROUND

Autoimmune enteropathy is normally characterised by crypt hyperplastic villous atrophy with enterocyte autoantibodies, activation of mucosal lymphocytes and increased epithelial HLA-DR. This case involved a severely affected Portuguese infant who was found to have lymphocyte activation deficiency and demonstrated correspondingly distinct mucosal features.

METHODS

A female infant of nonconsanguineous parents was treated for vomiting and diarrhoea, first with milk exclusion and then with parenteral nutrition. Lymphocyte subsets and immunoglobulin concentrations were normal, but in vitro testing showed no activation in response to phytohaemagglutinin, Candida, or purified protein derivative, although the response to interleukin (IL)-2 was intact. Interleukin-2 deficiency was excluded. Analysis of jejunal biopsy specimens revealed only mild villous blunting with absent goblet cells, normal epithelial proliferation, and no crypt hyperplasia. The dense infiltrate of CD8+ and CD4+ T lymphocytes showed normal CD2 and CD3 expression but no activation or proliferation markers. HLA-DR was not increased on epithelium or lymphocytes. Thus, in addition to in vitro evidence for lymphocyte activation deficiency, the mucosal specimens showed no evidence of in situ T-cell activation.

RESULTS

After development of overwhelming septicaemia, the patient died at 18 months, just before a planned bone marrow transplant.

CONCLUSIONS

These findings confirm significant heterogeneity within autoimmune enteropathy. Formal immune function testing should be performed in all affected infants to identify T-cell activation deficiencies. The distinct mucosal findings suggest that activated T cells usually induce the crypt hyperplastic villous atrophy characteristic of classic autoimmune enteropathy.