A structural abnormality of the abdomen ('belly'), that is, the part of the body between the pelvis and the thorax.

This syndrome has characteristics of holoprosencephaly, predominantly radial limb deficiency (absent thumbs, phocomelia), heart defects, kidney malformations and absence of gallbladder. It has been described in two families (with at least seven affected persons). Variable manifestations include vertebral anomalies, cleft lip/palate, microphthalmia, absent nose, dysplastic ears, hearing loss, colobomas of the iris and retina and/or bifid uvula. Inheritance is likely to be autosomal dominant with variable expressivity.

Because of their serious health problems, most individuals with Meckel syndrome die before or shortly after birth. Most often, affected infants die of respiratory problems or kidney failure.\n\nOther signs and symptoms of Meckel syndrome vary widely among affected individuals. Numerous abnormalities of the brain and spinal cord (central nervous system) have been reported in people with Meckel syndrome, including a group of birth defects known as neural tube defects. These defects occur when a structure called the neural tube, a layer of cells that ultimately develops into the brain and spinal cord, fails to close completely during the first few weeks of embryonic development. Meckel syndrome can also cause problems with development of the eyes and other facial features, heart, bones, urinary system, and genitalia.\n\nMeckel syndrome is a disorder with severe signs and symptoms that affect many parts of the body. The most common features are enlarged kidneys with numerous fluid-filled cysts; an occipital encephalocele, which is a sac-like protrusion of the brain through an opening at the back of the skull; and the presence of extra fingers and toes (polydactyly). Most affected individuals also have a buildup of scar tissue (fibrosis) in the liver.

X-linked intellectual disability-craniofacioskeletal syndrome is a rare, hereditary, syndromic intellectual disability characterized by craniofacial and skeletal abnormalities in association with mild intellectual disability in females and early postnatal lethality in males. In addition to mild cognitive impairment, females present with microcephaly, short stature, skeletal features and extra temporal lobe gyrus. In males, intrauterine growth impairment, cardiac and urogenital anomalies have been reported.

Mitchell-Riley syndrome is characterized by neonatal diabetes, pancreatic hypoplasia, intestinal atresia, and gallbladder aplasia or hypoplasia. There is considerable phenotypic overlap between Mitchell-Riley syndrome and Martinez-Frias syndrome (601346), the latter being characterized by the features of the Mitchell-Riley syndrome except for neonatal diabetes, and including tracheoesophageal fistula in some patients (Smith et al., 2010).

A rare, syndromic diabetes mellitus characterized by partial pancreatic agenesis, diabetes mellitus, and heart anomalies (including transposition of the great vessels, ventricular or atrial septal defects, pulmonary stenosis, or patent ductus arteriosis).

ZTTK syndrome (ZTTKS) is a severe multisystem developmental disorder characterized by delayed psychomotor development and intellectual disability. Affected individuals have characteristic dysmorphic facial features, hypotonia, poor feeding, poor overall growth, and eye or visual abnormalities. Most patients also have musculoskeletal abnormalities, and some have congenital defects of the heart and urogenital system. Brain imaging usually shows developmental abnormalities such as gyral changes, cortical and/or cerebellar atrophy, and thin corpus callosum (summary by Kim et al., 2016).

Short-rib thoracic dysplasia (SRTD) with or without polydactyly refers to a group of autosomal recessive skeletal ciliopathies that are characterized by a constricted thoracic cage, short ribs, shortened tubular bones, and a 'trident' appearance of the acetabular roof. SRTD encompasses Ellis-van Creveld syndrome (EVC) and the disorders previously designated as Jeune syndrome or asphyxiating thoracic dystrophy (ATD), short rib-polydactyly syndrome (SRPS), and Mainzer-Saldino syndrome (MZSDS). Polydactyly is variably present, and there is phenotypic overlap in the various forms of SRTDs, which differ by visceral malformation and metaphyseal appearance. Nonskeletal involvement can include cleft lip/palate as well as anomalies of major organs such as the brain, eye, heart, kidneys, liver, pancreas, intestines, and genitalia. Some forms of SRTD are lethal in the neonatal period due to respiratory insufficiency secondary to a severely restricted thoracic cage, whereas others are compatible with life (summary by Huber and Cormier-Daire, 2012 and Schmidts et al., 2013). There is phenotypic overlap with the cranioectodermal dysplasias (Sensenbrenner syndrome; see CED1, 218330).

Holoprosencephaly-12 with or without pancreatic agenesis (HPE12) is a developmental disorder characterized by abnormal separation of the embryonic forebrain (HPE) resulting in dysmorphic facial features and often, but not always, impaired neurologic development. Most patients with this form of HPE also have congenital absence of the pancreas, resulting in early-onset type 1 diabetes mellitus and requiring pancreatic enzyme replacement. Other features may include hearing loss and absence of the gallbladder (summary by De Franco et al., 2019 and Kruszka et al., 2019). For a phenotypic description and a discussion of genetic heterogeneity of holoprosencephaly, see HPE1 (236100).