A 37-kb Deletion in Region 16p13.3 in an Infant with Osteopetrosis and Congenital Diarrhea Including the CLCN7 and PERCC1 Genes.

Introduction: Congenital diarrhea presents a diagnostic challenge in cases where standard assessments are inconclusive. Case Presentation: We report a female infant with thrombocytopenia, increased bone density, and pale optic disc symptoms, suggestive of osteopetrosis. However, she also exhibited noninfectious, blood- and mucus-free diarrhea, not accounted for by osteopetrosis. Genetic testing, including clinical exome sequencing and chromosomal microarray analysis, revealed a homozygous 39-kb deletion on chromosome 16p13.3. This deletion spanned the CLCN7 gene associated with osteopetrosis and the PERCC1 gene implicated in congenital diarrhea. Conclusion: This case illustrates the importance of considering 16p13.3 deletions when confronted with the dual presentation of congenital diarrhea and osteopetrosis, expanding the diagnostic considerations for similar clinical presentations.

Revising pathogenesis of AP1S1-related MEDNIK syndrome: a missense variant in the AP1S1 gene as a causal genetic lesion.

MEDNIK syndrome is a rare autosomal recessive disease characterized by mental retardation, enteropathy, deafness, peripheral neuropathy, ichthyosis, and keratoderma, and caused by variants in the adaptor-related protein complex 1 subunit sigma 1 (AP1S1) gene. This gene encodes the σ1A protein, which is a subunit of the adaptor protein complex 1 (AP-1), a key component of the intracellular protein trafficking machinery. Previous work identified three AP1S1 nonsense, frameshift and splice-site variants in MEDNIK patients predicted to encode truncated σ1A proteins, with consequent AP-1 dysfunction. However, two AP1S1 missense variants (c.269 T > C and c.346G > A) were recently reported in patients who presented with severe enteropathy but no additional symptoms of MEDNIK. This condition was described as a novel non-syndromic form of congenital diarrhea caused specifically by the AP1S1 missense variants. In this study, we report two patients with the same c.269 T > C variant, who, contrary to the previous cases, presented as complete MEDNIK syndrome. These data substantially revise the presentation of disorders associated with AP1S1 gene variants and indicate that all the identified pathogenic AP1S1 variants result in MEDNIK syndrome. We also provide a series of functional analyses that elucidate the impact of the c.269 T > C variant on σ1A function, contributing to a better understanding of the molecular pathogenesis of MEDNIK syndrome. KEY MESSAGES: A missense AP1S1 c.269 T > C (σ1A L90P) variant causes full MEDNIK syndrome. The σ1A L90P variant is largely unable to assemble into the AP-1 complex. The σ1A L90P variant fails to bind [DE]XXXL[LI] sorting motifs. The σ1A L90P variant results in loss-of-function of the protein.

DGAT1 Mutation Associated With Congenital Diarrhea in a Pediatric Patient: A Case Report.

Chronic diarrhea in infants can stem from various etiologies, including congenital disorders affecting intestinal function. Here, we present a case of a one-year-old boy with persistent watery diarrhea, vomiting, and failure to thrive, ultimately diagnosed with DGAT1 deficiency through genetic testing. Despite initial investigations ruling out common causes like celiac disease, genetic analysis confirmed DGAT1 enteropathy. Management included intensive nutritional support and close monitoring, resulting in clinical improvement. This case underscores the importance of early genetic testing and tailored management in congenital enteropathies to prevent severe complications and improve patient outcomes.

A novel nutritional approach to infants and children with congenital diarrhea due to homozygous DGAT1 mutations.

OBJECTIVES: Diacylglycerol acyltransferase (DGAT) catalyzes the final step in triglyceride synthesis. DGAT1 is expressed in human enterocytes and is essential for fat absorption. Homozygous DGAT1 deficiency often presents with severe diarrhea and protein-losing enteropathy (PLE) in the 1st weeks of life. Because severe restriction of fat intake controls diarrhea and decreases PLE, total parenteral nutrition (TPN) was the initial standard therapy in infants and children. We present tertiary center experience managing infants and children with DGAT1 deficiency resulting in the development of a nutritional approach that minimizes the use of TPN. METHODS: From 2014 to 2020, 12 infants with DGAT1 deficiency were treated. Stool output, growth, and development, as well as essential fatty acid status, were monitored. This retrospective experience formed the basis for treatment recommendations, which include an ultralow fat formula with intermittent peripheral intravenous lipid infusions during the 1st year of life. RESULTS: All patients with prolonged intestinal fat exposure had PLE, which resolved when treated with the nutrition protocol. Essential fatty acid status as measured by triene:tetraene ratios normalized in all treated patients. Over time, early genetic diagnosis and prompt initiation of an ultralow fat diet with peripheral intravenous lipid infusions replaced the need for TPN. CONCLUSIONS: Children with DGAT1 deficiency respond to dietary restriction of lipids. Management with a novel nutritional approach provides effective treatment for infants with DGAT1 deficiency, treats diarrhea and PLE, promotes growth and development, avoids TPN dependency, and decreases the potential for essential fatty acid deficiency.

A Case Report on Tricho-Hepato-Enteric Syndrome: The SKIC3 Gene in Focus.

Tricho-hepato-enteric syndrome (THES), also known as syndromic diarrhea, is a rare genetic disorder that causes intractable diarrhea, hair anomalies, facial dysmorphism, and liver abnormalities. Herein, we report the case of an eight-month-old male who was referred to our hospital due to symptoms of diarrhea, vomiting, and insufficient weight gain. The child was born via cesarean section following an uncomplicated pregnancy, with no history of admission to the neonatal intensive care unit (NICU). Since birth, the patient has been experiencing diarrhea and inadequate weight gain, necessitating multiple hospital admissions. Upon evaluation, genetic testing confirmed the diagnosis of THES. The management strategy included a variety of nutritional interventions and supportive care measures. Currently, the patient is in the pediatric intensive care unit (PICU), receiving total parenteral nutrition (TPN) and continuous supportive care. This case underscores the complexity of diagnosing and managing THES, highlighting the need for comprehensive care and close monitoring of the patient's condition.

Congenital sucrase-isomaltase deficiency in Türkiye; a single center experience.

BACKGROUND: Congenital sucrase-isomaltase deficiency (CSID) is a rare inherited carbohydrate malabsorption disorder caused by sucrase-isomaltase (SI) gene variants. In CSID, an autosomal recessively inherited disease, symptoms can also be seen in individuals with heterozygous mutations. METHODS: The variant spectrum was evaluated retrospectively in individuals who presented with chronic diarrhea between 2014 and 2022 and had undergone genetic testing of the SI gene considering CSID due to diet-related complaints. RESULTS: Ten patients with chronic diarrhea were genetically evaluated with SI gene sequencing. In patients diagnosed with CSID and whose symptoms improved with enzyme replacement therapy, the genetic mutation zygosity was found to be heterozygous at a rate of 90%. In 10% of the patients, the mutation was homozygous. Limiting consuming sucrose and isomaltose foods reduced the patients' complaints, but the symptoms did not disappear completely. With the initiation of sacrosidase enzyme replacement therapy, the patient's complaints completely disappeared. CONCLUSION: In CSID, defined as an autosomal recessive disease, clinical symptoms can also be seen in heterozygous cases previously described as carriers, and these patients also benefit from sacrosidase enzyme replacement therapy. In light of these findings, the autosomal recessive definition of CSID does not fully characterize the disease.What is Known:CSID is a rare inherited carbohydrate malabsorption disorder caused by sucrase-isomaltase gene variants.In congenital sucrase-isomaltase deficiency, an autosomal recessively inherited disorder, symptoms can also be seen in individuals with heterozygous mutations.What is new:Severe disease symptoms can also be seen in heterozygous cases, which were thought to be carriers because the disease was previously described as autosomal recessive.Sacrosidase enzyme replacement therapy also eliminates the disease symptoms in patients with heterozygous CSID mutations.This is the second study on sucrase-isomaltase enzyme deficiency pediatric groups in Türkiye and Europe.

This is the study to evaluate the congenital sucrase-isomaltase enzyme deficiency in chronic diarrhea cases covering adults and childhood in our country and the clinical features and treatment response characteristics of the variants detected in these patients.In addition, another aim of our study is that sucrase­isomaltase enzyme deficiency should be considered in the differential diagnosis and should be kept in mind, especially in cases with chronic diarrhea whose cause cannot be determined in childhood.

Newly Described Mutations of the UNC45A Gene in Infants with Jaundice and Pruritus.

BACKGROUND: Cholestatic liver disease is an important cause of morbidity and mortality and a leading indication for liver transplantation in children. These include diseases, such as biliary atresia, Alagille syndrome, progressive familial intrahepatic cholestasis, sclerosing cholangitis, bile acid synthesis defects, and many others. CASE PRESENTATION: NGS was used as a diagnostic tool to identify the genetic cause in the patient with cholestatic syndrome and to figure out and describe what mutation will be found. In the present observation, the cholestasis syndrome with low GGT activity and intense pruritus was the leading symptom of the patient. The examination also revealed other characteristic features of osteo- oto-hepato-enteric syndrome. The patient had facial features that mimicked Alagille syndrome, which complicated the diagnostic search. Moreover, the genetic test revealed two new pathogenic variants in the UNC45A gene. CONCLUSION: This clinical observation demonstrates the importance of a multidisciplinary approach in the diagnosis of rare genetic diseases and using WES, which can accelerate the diagnosis compared with outdated gene panels.

Biallelic variants of the first Kunitz domain of SPINT2 cause a non-syndromic form of congenital diarrhea and tufting enteropathy.

Biallelic SPINT2 pathogenic variants cause a syndromic form of congenital diarrhea and enteropathy (OMIM 270420). To date, 35 patients have been reported and all presented with additional extra-intestinal features, apart from one case. We report on a 5-year-old girl who presented early in life with diarrhea and was found to have a novel homozygous variant in SPINT2. Pathological studies confirmed tufting enteropathy, and during her 5 years of life, she has not developed any extra-intestinal features. Molecular analysis detected a homozygous variant (NM_021102.4: c.203A>G (p. [Tyr68Cys]) in SPINT2. This is the first missense variant reported in the first Kunitz domain (KD1) of SPINT2 in humans. In vitro functional studies of this variant confirmed the deleterious effect leading to the loss of inhibitory activity of the intestinal serine proteases. This is the first description of SPINT2-related diarrhea in a patient who lived without long-term total parenteral nutrition. This study expands the clinical and molecular characteristics of SPINT2-related conditions.

Approach to a Child with Chronic Diarrhea.

Chronic diarrhea in children is challenging both with regards to etiological diagnosis and for management. Etiology and pathophysiological mechanisms vary widely from neonates to adolescents. Congenital or genetic causes are more frequent in neonates, while infections, allergy and immune-mediated mechanisms are more frequent in childhood. A thorough history and proper physical examination are required to decide for further diagnostic evaluation. The approach to a child with chronic diarrhea should be age specific and based predominantly on the pathophysiological mechanism involved. The nature of the stool like watery, bloody or fatty (steatorrhea) can suggest the probable etiology and organ system involved. After routine tests, evaluation with specific serological tests, imaging, endoscopy (gastroscopy/colonoscopy), histopathology of intestinal mucosa, breath tests or radionuclide imaging may be required to make a definitive diagnosis. Genetic evaluation is important in congenital diarrheas, monogenic inflammatory bowel disease (IBD) and immunodeficiency disorders. Management is aimed at stabilization, nutritional support and etiology specific treatment. Specific therapy can be as simple as exclusion of specific nutrient or as complicated as small bowel transplant. Evaluation and management require expertise and thus patients need to be referred in a timely fashion. This will minimise morbidity including nutritional consequences and improve outcome.

Approach to Congenital Diarrhea and Enteropathies (CODEs).

Congenital diarrhea and enteropathies (CODEs) constitute a group of rare genetic disorders characterized by severe diarrhea and malabsorption in the neonatal period or early infancy. Timely diagnosis and treatment is essential to prevent life-threatening complications, including dehydration, electrolyte imbalance, and malnutrition. This review offers a simplified approach to the diagnosis of CODEs, with a specific focus on microvillus inclusion disease (MVID), congenital tufting enteropathy (CTE), congenital chloride diarrhea (CLD), and congenital sodium diarrhea (CSD). Patients with CODEs typically present with severe watery or occasionally bloody diarrhea, steatorrhea, dehydration, poor growth, and developmental delay. Therefore, it is crucial to thoroughly evaluate infants with diarrhea to rule out infectious, allergic, or anatomical causes before considering CODEs as the underlying etiology. Diagnostic investigations for CODEs encompass various modalities, including stool tests, blood tests, immunological studies, endoscopy and biopsies for histology and electron microscopy, and next-generation sequencing (NGS). NGS plays a pivotal role in identifying the genetic mutations responsible for CODEs. Treatment options for CODEs are limited, often relying on total parenteral nutrition for hydration and nutritional support. In severe cases, intestinal transplantation may be considered. The long-term prognosis varies among specific CODEs, with some patients experiencing ongoing intestinal failure and associated complications. In conclusion, the early recognition and accurate diagnosis of CODEs are of paramount importance for implementing appropriate management strategies. Further research and advancements in genetic testing hold promise for enhancing diagnostic accuracy and exploring potential targeted therapies for these rare genetic disorders.

Novel Mutation in the SLC5A1 Gene Causing Glucose-Galactose Malabsorption: First Confirmed Case From Central America.

Congenital glucose-galactose malabsorption is a rare cause of life-threatening diet-induced diarrhea in infants. Mutations in the SLC5A1 gene, which encodes for the sodium-dependent glucose transporter, result in large-volume diarrhea due to aberrant glucose and galactose transport across the intestinal brush border. The diagnosis can be made clinically based on the presence of diarrhea soon after birth, evidence of carbohydrate malabsorption in the stool, and resolution of diarrhea with dietary elimination of glucose and galactose. Genetic testing can confirm the diagnosis. Here we report the first confirmed case of glucose-galactose malabsorption in an infant from Central America due to a novel mutation in the SLC5A1 gene. The patient began growing and thriving after being diagnosed and with the correct dietary interventions.

Congenital Sodium Diarrhea: Antenatal Diagnosis May Prevent Unnecessary Surgery in the Neonate.

Congenital sodium diarrhea (CSD) is a rare, life-threatening condition characterized by intractable diarrhea, hyponatremia, and metabolic acidosis. It presents similarly to other congenital disorders and, therefore, is often misdiagnosed and mistreated. We present a case of CSD that presented with dilated loops of bowel and polyhydramnios at 18 weeks and was thought to be a congenital bowel obstruction. The patient was therefore managed surgically after birth with a diverting ileostomy, however was later found to have elevated stool sodium levels and metabolic derangements consistent with CSD. Our case demonstrates the need for high index of suspicion for congenital diarrheal disorders to prevent unnecessary surgery and a delay in appropriate medical management of this rare condition.

Case report: Diagnosis and treatment of DGAT1 deficiency-induced congenital diarrhea in two cases and literature review.

Introduction: Congenital diarrhea is a rare inherited intestinal disease characterized by persistent and severe diarrhea and malabsorption in the first few weeks after birth, which can be life-threatening. Some congenital diarrheal diseases are associated with mutations in the diacylglycerol acyltransferase 1 (DGAT1) gene. Case descriptions: This study delineated 2 cases of diarrhea and growth retardation, subsequently confirmed as congenital diarrhea via genetic testing, revealing that the etiology involved compound heterozygous mutations in the DGAT1 gene. Diagnostic assessments: High-MCT milk powder did not obtain an ideal outcome, whereas low-fat diets improved the symptoms of diarrhea and increased the body weigths. Disscussion: The two cases facilitated our understanding of the clinical features of, and treatments for, patients harboring a DGAT1 mutation and enriched the existing DGAT1 mutation database.

Diet and Management of Diarrhea.

Diet plays an important role in human health and disease. Of all human diseases, diarrheal illnesses bring diet into sharp focus as it has a direct causal and therapeutic relationship. With the advent and widespread use of next generation sequencing, significant advances have been made in unraveling the etiologies of congenital diarrheas and enteropathies, some of which are eminently treatable with dietary modification. Early institution of appropriate dietary therapy is lifesaving in congenital osmotic diarrheas. Chronic diarrhea in older children and adolescents often have an underlying dietary basis, depending on the etiology. Identification and exclusion of the offending food in the diet results in dramatic improvement in symptoms. It is equally important to be prudent and cautious in the use of exclusion diets in management of chronic diarrhea as it is associated with micronutrient deficiencies, needless escalation of cost and enable maladaptive food intake behaviors. In this review, authors discuss etiology specific dietary management of diarrhea in children with emphasis on congenital diarrheas and enteropathies.

Fetal Bowel Abnormalities Suspected by Ultrasonography in Microvillus Inclusion Disease: Prevalence and Clinical Significance.

Microvillus inclusion disease (MVID) is a rare, inherited, congenital, diarrheal disorder that is invariably fatal if left untreated. Within days after birth, MVID presents as a life-threatening emergency characterized by severe dehydration, metabolic acidosis, and weight loss. Diagnosis is cumbersome and can take a long time. Whether MVID could be diagnosed before birth is not known. Anecdotal reports of MVID-associated fetal bowel abnormalities suspected by ultrasonography (that is, dilated bowel loops and polyhydramnios) have been published. These are believed to be rare, but their prevalence in MVID has not been investigated. Here, we have performed a comprehensive retrospective study of 117 published MVID cases spanning three decades. We find that fetal bowel abnormalities in MVID occurred in up to 60% of cases of MVID for which prenatal ultrasonography or pregnancy details were reported. Suspected fetal bowel abnormalities appeared in the third trimester of pregnancy and correlated with postnatal, early-onset diarrhea and case-fatality risk during infancy. Fetal bowel dilation correlated with MYO5B loss-of-function variants. In conclusion, MVID has already started during fetal life in a significant number of cases. Genetic testing for MVID-causing gene variants in cases where fetal bowel abnormalities are suspected by ultrasonography may allow for the prenatal diagnosis of MVID in a significant percentage of cases, enabling optimal preparation for neonatal intensive care.

Apoptotic enteropathy, gluten intolerance, and IBD-like inflammation associated with lipotoxicity in DGAT1 deficiency-related diarrhea: a case report of a 17-year-old patient and literature review.

We present a long-term follow-up in a 17-year-old girl with DGAT1-related diarrhea, an autosomal recessive disorder characterized by impaired triglyceride absorption. Neonatal presentation included severe congenital diarrhea, protein-losing enteropathy, and failure to thrive requiring total parenteral nutrition. Duodenal biopsies revealed apoptotic enteropathy and acute inflammation with the presence of macrophages and Touton giant cells, related to the intake of fat. She was able to switch to enteral nutrition on a fat-free diet. However, at age 10, she developed gluten-induced enteropathy and then IBD-like inflammation 5 years later. Immunohistochemistry was able to confirm the diagnosis, while DGAT1 sequencing remained inconclusive. This highlights the role of histopathology and immunohistochemistry, despite the increasing importance of genetic analysis in the diagnostic work-up. This report also illustrates that parenteral nutrition weaning is possible in DGAT1-related diarrhea, but gut barrier dysfunction might increase the risk of autoimmune intestinal disease.

Malabsorption Syndromes and Food Intolerance.

Feeding intolerance is ubiquitous in neonatal intensive care units with as many signs and symptoms as possible diagnoses. Optimizing nutrition is paramount in both preterm and term infants. Determining the cause of feeding intolerance and adjusting nutrition interventions is an important part of the daily care of newborns. This review discusses the role of malabsorption and food intolerance as possible causes of nutrition difficulties in the newborn.

Altered MYO5B Function Underlies Microvillus Inclusion Disease: Opportunities for Intervention at a Cellular Level.

Microvillus inclusion disease (MVID) is a congenital diarrheal disorder resulting in life-threatening secretory diarrhea in newborns. Inactivating and nonsense mutations in myosin Vb (MYO5B) have been identified in MVID patients. Work using patient tissues, cell lines, mice, and pigs has led to critical insights into the pathology of MVID and a better understanding of both apical trafficking in intestinal enterocytes and intestinal stem cell differentiation. These studies have demonstrated that loss of MYO5B or inactivating mutations lead to loss of apical sodium and water transporters, without loss of apical CFTR, accounting for the major pathology of the disease. In addition, loss of MYO5B expression induces the formation of microvillus inclusions through apical bulk endocytosis that utilizes dynamin and PACSIN2 and recruits tight junction proteins to the sites of bulk endosome formation. Importantly, formation of microvillus inclusions is not required for the induction of diarrhea. Recent investigations have demonstrated that administration of lysophosphatidic acid (LPA) can partially reestablish apical ion transporters in enterocytes of MYO5B KO mice. In addition, further studies have shown that MYO5B loss induces an imbalance in Wnt/Notch signaling pathways that can lead to alterations in enterocyte maturation and tuft cell lineage differentiation. Inhibition of Notch signaling leads to improvements in those cell differentiation deficits. These studies demonstrate that directed strategies through LPA receptor activation and Notch inhibition can bypass the inhibitory effects of MYO5B loss. Thus, effective strategies may be successful in MVID patients and other congenital diarrhea syndromes to reestablish proper apical membrane absorption of sodium and water in enterocytes and ameliorate life-threatening congenital diarrhea.

Congenital disorders of intestinal digestion and absorption (sugars, proteins, lipids, ions).

Congenital diarrhea may result from 2 main different mechanisms: 1) osmotic diarrhea is caused by the non-digestion-absorption of nutrients leading to the non-absorbed nutrients going into the lumen, increasing the osmotic force and driving fluids; 2) secretory diarrhea induced by the inhibition of intestinal absorption of electrolytes, increasing electrolyte and water flux towards the intestinal lumen. The malabsorption of macronutrients (carbohydrates, proteins and lipids) induces energy deficiency with symptoms depending on the macronutrient: carbohydrates with watery acidic diarrhea; protein with rapid malnutrition, edema, and hypoalbuminemia; and lipids with malnutrition, steatorrhea and hypocholesterolemia. Ionic malabsorption (Cl and Na) is responsible for severe and rapid dehydration sometimes with prenatal abnormalities (polyhydramnios and bowel dilatation).

Delayed Diagnosis in a Male With Congenital Chloride Losing Diarrhea.

Congenital chloride diarrhea is a secretory type of diarrhea, inherited in as autosomal recessive. Our case involves a 12-month-old male who initially presented in infancy and was treated with an exclusive elemental formula diet. At 12 months of age, he presented with significant hypokalemia, hypochloremia, and metabolic alkalosis. The diagnosis was established with stool electrolytes demonstrating a stool chloride of 145 mmol/L. He initially was treated with sodium and potassium supplementation and a proton pump inhibitor. Genetic testing revealed a large 4.3-kb deletion encompassing exons 15 to 17 of the SLC26A3 gene and a sequence variant of the SLC26A3 gene, c.610T>G; pTyr204Asp initially reported as a variant of unknown significance. His parents had genetic testing confirming that the deletion and sequence variant were found in opposite alleles in the patient, meaning the sequence variant is a pathogenic variant. He is maintaining stable serum electrolytes and gaining appropriate weight on oral electrolyte supplementation.