Monosomy 18p

18p- is a genetic condition caused by a deletion of all or part of the short arm (the p arm) of chromosome 18. It occurs in about 1 of every 50,000 births. 18p- is a genetic condition caused by a deletion of all or part of the short arm (the p arm) of chromosome 18. It occurs in about 1 of every 50,000 births. 18p- causes a wide range of medical and developmental concerns. There is significant variation in severity. This variation is due to the variability of the deletion size and breakpoints. About 10-15% of individuals with 18p- have holoprosencephaly. Approximately 10% of people with 18p- have a congenital heart anomaly. There does not appear to be a specific type of heart defect associated with a deletion of the short arm of chromosome 18. Septal defects, tetralogy of Fallot, dextrocardia, and coarctation of the aorta have all been reported in infants with 18p-. Hypotonia is frequently seen in the 18p- population. Seizures, though uncommon, have been reported in people with 18p-. Dystonia has also been diagnosed in a small minority of young adults with 18p-. Also, tethered cord has been reported in a few people with 18p-. Ptosis is quite common among people with 18p-. In many cases, surgical correction is required. Refractive errors, such as myopia, hyperopia, and astigmatism, are also prevalent. Strabismus has been reported in infants and children with 18p-. Nystagmus is also present in a minority of individuals. Children with 18p- have an increased incidence of ear infections, often requiring the placement of PE tubes. Conductive hearing loss may occur due to otitis media. Chronic constipation is a frequent complaint in the 18p- population. Other abdominal abnormalities that have been reported include inguinal hernias; malrotation of the gut; and abnormalities of the spleen.