21q deletion syndrome

21q deletion syndrome, also known as monosomy 21q or partial deletion of the long arm of chromosome 21, is a rare chromosomal disorder caused by the loss (deletion) of genetic material from the long arm (q arm) of chromosome 21. The clinical presentation varies considerably depending on the size and precise location of the deleted segment. Common features include intellectual disability of variable severity, growth retardation, microcephaly, and a range of craniofacial dysmorphisms such as a broad nasal bridge, downslanting palpebral fissures, low-set ears, and micrognathia. Skeletal anomalies, congenital heart defects, and genitourinary malformations may also be present. Hypotonia is frequently observed in infancy, and psychomotor development is typically delayed. The severity of the condition correlates with the extent of the deletion. Larger terminal deletions tend to produce more significant clinical manifestations, while smaller interstitial deletions may result in milder phenotypes. Some patients may also exhibit thrombocytopenia or other hematologic abnormalities, particularly when the deletion involves the distal region of 21q that encompasses genes critical for platelet function and megakaryocyte development. Respiratory and feeding difficulties may be present in the neonatal period. There is no cure for 21q deletion syndrome, and management is supportive and symptom-based. Treatment typically involves a multidisciplinary approach including early intervention programs, speech and occupational therapy, physical therapy, and special education services. Cardiac defects may require surgical correction, and regular monitoring by specialists in cardiology, neurology, and endocrinology is often recommended. Genetic counseling is important for affected families to understand recurrence risks and the nature of the chromosomal abnormality.

Common questions about 21q deletion syndrome