Hypomyelinating leukodystrophy-3 (HLD3) is an autosomal recessive severe neurologic disorder characterized by early infantile onset of global developmental delay, lack of development, lack of speech acquisition, and peripheral spasticity associated with decreased myelination in the central nervous system (summary by Feinstein et al., 2010). The disorder is phenotypically similar to X-linked Pelizaeus-Merzbacher disease (PMD; 312080), which is caused by mutation in the PLP1 gene (300401). For a general phenotypic description and a discussion of genetic heterogeneity of HLD, see 312080.

Infantile pyloric stenosis is the most common condition requiring surgical intervention in the first year of life. It typically presents in infants 2 to 6 weeks after birth. Clinically the disorder is characterized by projectile vomiting, visible gastric peristalsis, and a palpable pyloric tumor (summary by Everett et al., 2008). Mortality was high until successful treatment by pyloromyotomy was developed by Ramstedt (1912). Genetic Heterogeneity of Infantile Hypertrophic Pyloric Stenosis Multiple susceptibility loci have been implicated in IHPS including IHPS1 on chromosome 12q, IHPS2 (610260) on chromosome 16p13-p12, IHPS3 (612017) on chromosome 11q14-q22, IHPS4 (300711) on chromosome Xq23, and IHPS5 (612525) on chromosome 16q24.

A rare intestinal disorder of neonates of unknown etiology. Patients are born with a short small bowel (less than 75 cm in length) that compromises proper intestinal absorption and leads chronic diarrhea, vomiting and failure to thrive.

Intestinal dysmotility syndrome (IDMTS) is an autosomal recessive disorder characterized by impaired intestinal motility resulting in episodes of diarrhea and distention of intestinal loops. Intestinal and hepatic portal venous gas, similar to findings seen in necrotizing enterocolitis, may be present. Dysmorphic features and developmental delay may also be present (Park et al., 2021).