Ring chromosome 22 syndrome

Ring chromosome 22 syndrome (also known as r(22) syndrome) is a rare chromosomal disorder caused by the formation of a ring chromosome 22, in which both ends of chromosome 22 are deleted and the remaining segments fuse to form a circular (ring) structure. This results in partial monosomy of chromosome 22, with the clinical severity depending on the amount of genetic material lost during ring formation. The condition affects multiple body systems, most notably the nervous system, and is classified under ICD-10 code Q93.2 (chromosome replaced with ring, dicentric, or isochromosome). Key clinical features include intellectual disability of variable severity, developmental delay, speech and language impairment, hypotonia (low muscle tone), and behavioral difficulties. Many affected individuals exhibit features overlapping with Phelan-McDermid syndrome (22q13.3 deletion syndrome) because ring chromosome 22 formation frequently involves loss of the distal long arm of chromosome 22, including the SHANK3 gene. Additional features may include epicanthal folds, large ears, long eyelashes, full eyebrows, and minor facial dysmorphisms. Some patients experience seizures, and a subset may develop tumors associated with loss of the NF2 gene on chromosome 22, including schwannomas and meningiomas, particularly when the ring chromosome is unstable and prone to mitotic loss. There is no cure for ring chromosome 22 syndrome. Management is supportive and multidisciplinary, involving early intervention programs, speech therapy, occupational therapy, physical therapy, and behavioral support. Seizures are managed with standard antiepileptic medications. Surveillance for NF2-related tumors may be recommended depending on the extent of genetic material lost. Regular developmental and neurological assessments are important components of ongoing care.

Common questions about Ring chromosome 22 syndrome