Distal 18q- is a genetic condition caused by a deletion of genetic material within one of the two copies of chromosome 18. The deletion involves the distal section of 18q and typically extends to the tip of the long arm of chromosome 18. Presentation Distal 18q- causes a wide range of medical and developmental concerns, with significant variation in severity due to the variation in breakpoints reported in individuals with distal 18q-. Current research is focused on establishing genotype-phenotype correlations to enable predictive genotyping. Congenital anomalies Heart abnormalities are present in 25–35% of people with distal 18q-. The majority of these defects are septal. Congenital orthopedic anomalies are also relatively common, particularly rocker-bottom feet or clubfoot. Cleft lip and palate are relatively common in people with distal 18q-. Kidney abnormalities have also been reported and include horseshoe kidney, hydronephrosis, polycystic kidney, and absent kidney. Boys with distal 18q- may have genital anomalies, the most frequent being cryptorchidism and hypospadias. Neurologic Hypotonia is a common finding. Around 10% of people with distal 18q- have seizures. MRI abnormalities Dysmyelination is a common finding in people with distal 18q-, present in about 95%. Hypoplasia of the corpus callosum is also a common finding. Vision Strabismus and nystagmus are prevalent in distal 18q-. Changes in the optic nerve, as well as colobomas, are also fairly common. Myopia has been reported in some individuals. Ear and sinus infections Due to changes in facial structures, infants, toddlers, and children with distal 18q- often have poor drainage from the middle ears, leading to a build-up of fluid. This can in turn lead to recurrent ear and sinus infections. Antibiotics are typically required to treat these infections. In addition, the diagnosis of ear infections in children with 18q- is frequently complicated by stenosis or atresia of the ear canals, a common finding in people with distal 18q-. Hearing People with distal 18q- frequently have conductive and/or sensorineural hearing loss. The degree of hearing loss may vary from mild to severe. Gastrointestinal Individuals with distal 18q- may have problems with reflux. Hernias have also been reported. Genitourinary As mentioned above, males with distal 18q- may have cryptorchidism. Hypospadias and chordee have also been reported. Also, a variety of kidney malformations have been reported in infants with distal 18q-, as noted above. Additionally, vesicouretereral reflux has been diagnosed in several people with distal 18q-. Orthopedics As mentioned above, distal 18q-