Monosomy 18p syndrome

Monosomy 18p syndrome, also known as deletion 18p syndrome or 18p minus syndrome (18p-), is a rare chromosomal disorder caused by partial or complete deletion of the short arm (p) of chromosome 18. This condition affects multiple body systems and is characterized by a wide spectrum of clinical features that vary in severity among affected individuals. The most common features include mild to moderate intellectual disability, short stature, and distinctive craniofacial characteristics such as a round face, ptosis (drooping eyelids), wide mouth with downturned corners, broad flat nasal bridge, and low-set ears. Many individuals exhibit muscular hypotonia (reduced muscle tone) in infancy, which may contribute to delayed motor milestones. Speech and language development are frequently delayed. Some patients may have holoprosencephaly (a brain malformation involving incomplete division of the forebrain), which can range from mild to severe. Additional features may include skeletal anomalies, dental abnormalities, and, less commonly, congenital heart defects or genitourinary malformations. Growth hormone deficiency and other endocrine abnormalities, including IgA deficiency, have been reported in some cases. There is no cure for monosomy 18p syndrome, and management is supportive and symptom-based. Treatment may include early intervention programs, speech therapy, physical therapy, occupational therapy, and special education services. Growth hormone therapy may be considered for individuals with documented growth hormone deficiency. Regular monitoring by a multidisciplinary team including geneticists, neurologists, endocrinologists, and developmental specialists is recommended to address the various medical and developmental needs of affected individuals.

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