Gastroesophageal reflux (GER) is characterized by the retrograde movement of stomach contents into the esophagus. In its most severe form, GER results in extensive tissue damage caused by acid reflux. In adolescents and adults, and even infrequently in children, chronic GER is associated with the risk of developing Barrett metaplasia (614266), a premalignant lesion of the esophageal mucosa (Hu et al., 2000). In turn, Barrett metaplasia is correlated with the development of adenocarcinoma of the esophagus (see 614266), estimated as the fifth most prevalent neoplasia in the Western world (Lagergren et al., 1999).

Multiple endocrine neoplasia type 1 (MEN1) includes varying combinations of more than 20 endocrine and non-endocrine tumors. Endocrine tumors become evident either by overproduction of hormones by the tumor or by growth of the tumor itself. Parathyroid tumors are the most common MEN1-associated endocrinopathy; onset in 90% of individuals is between ages 20 and 25 years with hypercalcemia evident by age 50 years; hypercalcemia causes lethargy, depression, confusion, anorexia, constipation, nausea, vomiting, diuresis, dehydration, hypercalciuria, kidney stones, increased bone resorption/fracture risk, hypertension, and shortened QT interval. Pituitary tumors include prolactinoma (the most common), which manifests as oligomenorrhea/amenorrhea and galactorrhea in females and sexual dysfunction in males. Well-differentiated endocrine tumors of the gastroenteropancreatic (GEP) tract can manifest as Zollinger-Ellison syndrome (gastrinoma); hypoglycemia (insulinoma); hyperglycemia, anorexia, glossitis, anemia, diarrhea, venous thrombosis, and skin rash (glucagonoma); and watery diarrhea, hypokalemia, and achlorhydria syndrome (vasoactive intestinal peptide [VIP]-secreting tumor). Carcinoid tumors are non-hormone-secreting and can manifest as a large mass after age 50 years. Adrenocortical tumors can be associated with primary hypercortisolism or hyperaldosteronism. Non-endocrine tumors include facial angiofibromas, collagenomas, lipomas, meningiomas, ependymomas, and leiomyomas.

Diamond-Blackfan anemia (DBA) is characterized by a profound normochromic and usually macrocytic anemia with normal leukocytes and platelets, congenital malformations in up to 50%, and growth deficiency in 30% of affected individuals. The hematologic complications occur in 90% of affected individuals during the first year of life. The phenotypic spectrum ranges from a mild form (e.g., mild anemia or no anemia with only subtle erythroid abnormalities, physical malformations without anemia) to a severe form of fetal anemia resulting in nonimmune hydrops fetalis. DBA is associated with an increased risk for acute myelogenous leukemia (AML), myelodysplastic syndrome (MDS), and solid tumors including osteogenic sarcoma.

Autosomal recessive limb-girdle muscular dystrophy-18 (LGMDR18) is characterized by childhood-onset of proximal muscle weakness resulting in gait abnormalities and scapular winging. Serum creatine kinase is increased. A subset of patients may show a hyperkinetic movement disorder with chorea, ataxia, or dystonia and global developmental delay (summary by Bogershausen et al., 2013). Additional more variable features include alacrima, achalasia, cataracts, or hepatic steatosis (Liang et al., 2015; Koehler et al., 2017). For a discussion of genetic heterogeneity of autosomal recessive limb-girdle muscular dystrophy, see LGMDR1 (253600).

Eosinophilic esophagitis (EOE) has an incidence of approximately 1 per 10,000 people. Symptoms include difficulty feeding, failure to thrive, vomiting, epigastric or chest pain, dysphagia, and food impaction. Individuals with EOE are predominantly young males with a high rate of atopic disease, and the diagnosis is made by endoscopy and biopsy findings of isolated eosinophils in the esophagus (summary by Rothenberg et al., 2010). Genetic Heterogeneity of Eosinophilic Esophagitis Eosinophilic esophagitis-1 (EOE1) is associated with variation at chromosome 7q11.2. Another locus (EOE2; 613412) has been been associated with variation in the TSLP gene (607003) on chromosome 5q22.

Immunodeficiency-58 is an autosomal recessive primary immunologic disorder characterized by early-onset skin lesions, including eczematous dermatitis, infectious abscesses, and warts, recurrent respiratory infections or allergies, and chronic persistent infections with candida, Molluscum contagiosum, mycobacteria, EBV, bacteria, and viruses. Some patients may have gastrointestinal involvement, including inflammatory bowel disease, EBV+ smooth muscle tumors, and esophagitis. Immunologic analysis shows defective T-cell function with decreased Treg cells and deficient CD3/CD28 costimulation responses in both CD4+ and CD8+ T cells. B-cell function may also be impaired (summary by Wang et al., 2016 and Alazami et al., 2018).

Inflammatory bowel disease-30 (IBD30) is characterized by abdominal pain and watery or bloody diarrhea, with changes in the intestinal tract consistent with Crohn disease (Mao et al., 2018). For a general description and a discussion of genetic heterogeneity of inflammatory bowel disease, including Crohn disease (CD) and ulcerative colitis (UC), see IBD1 (266600).

Visceral myopathy-2 (VSCM2) is characterized by gastrointestinal symptoms resulting from intestinal dysmotility and paresis, including abdominal distention, pain, nausea, and vomiting. Some patients exhibit predominantly esophageal symptoms, with hiatal hernia and severe reflux resulting in esophagitis and stricture, whereas others experience chronic intestinal pseudoobstruction. Bladder involvement resulting in megacystis and megaureter has also been observed and may be evident at birth (Dong et al., 2019; Gilbert et al. (2020)).

Immunodeficiency-92 (IMD92) is an autosomal recessive primary immunodeficiency characterized by the onset of recurrent infections in infancy or early childhood. Infectious agents are broad, including bacterial, viral, fungal, and parasitic, including Cryptosporidium and Mycobacteria. Patient lymphocytes show defects in both T- and B-cell proliferation, cytokine secretion, and overall function, and there is also evidence of dysfunction of NK, certain antigen-presenting cells, and myeloid subsets. Hematopoietic stem cell transplantation may be curative (summary by Beaussant-Cohen et al., 2019 and Levy et al., 2021).

X-linked familial Behcet-like autoinflammatory syndrome-2 (AIFBL2) is an X-linked recessive disorder characterized by the onset of inflammatory symptoms in the first decade of life in male patients. Affected males often present with oral mucosal ulceration and skin inflammation. More variable features may include gastrointestinal ulceration, arthritis, recurrent fevers, and iron deficiency anemia. Laboratory studies are consistent with immune dysregulation manifest as increased inflammatory markers and variable immune cell abnormalities, such as decreased NK cells and low memory B cells. One patient presented with recurrent infections and immunodeficiency in addition to autoinflammation. The disorder results from a defect in ELF4, which normally acts as a negative regulator of inflammatory disease. Symptoms may respond to blockade of IL1 (see 147760) or TNFA (191160) (summary by Tyler et al., 2021 and Sun et al., 2022). For a discussion of genetic heterogeneity of AIFBL, see AIFBL1 (616744).

X-linked syndromic intellectual developmental disorder-37 (MRXS37) is a developmental disorder showing phenotypic variability and variable severity. Male mutation carriers tend to be more severely affected than female mutation carriers, some of whom may even be asymptomatic. In general, the disorder is characterized by global developmental delay with delayed walking, speech delay, impaired intellectual development that ranges from borderline low to moderate, and behavioral abnormalities, such as autism and sleeping difficulties. Many patients are able to attend mainstream schools with assistance and work under supervision. Additional more variable features include sensorineural hearing loss, ocular anomalies, feeding difficulties, dysmorphic facial features, inguinal and umbilical hernia, genitourinary defects, congenital heart defects, musculoskeletal anomalies, and endocrine dysfunction, such as hypogonadism or hyperparathyroidism (Shepherdson et al., 2024).