Autosomal ring chromosomes in human genetic disorders

Area of Science:

• Genetics
• Clinical Genetics
• Chromosomal Abnormalities

Background:

• Ring chromosomes result from breakage and rejoining of chromosome arms, leading to variable genetic content and size.
• Phenotypes are diverse due to deletions during ring formation and potential imbalances from ring instability.
• Ring chromosome 20 is notably linked to early-onset epilepsy, while growth deficiency is a common feature across various ring chromosomes, termed "ring syndrome".

Purpose of the Study:

• To summarize the characteristics and clinical implications of ring chromosomes.
• To highlight the association of ring chromosome 20 with epilepsy.
• To discuss the challenges in genotype-phenotype correlation and the importance of prenatal diagnosis.

Main Methods:

• Literature review and synthesis of existing data on ring chromosomes.
• Analysis of phenotypic variability and associated genetic factors.
• Discussion of clinical management and diagnostic considerations.

Main Results:

• Ring chromosomes are heterogeneous, with phenotypes influenced by deletion extent, ring instability, and mosaicism.
• Severe growth deficiency is a common feature, independent of the specific chromosome involved.
• Ring chromosome 20 shows a significant association with early-onset epilepsy.

Conclusions:

• Precise genotype-phenotype correlations for ring chromosomes are challenging due to multiple influencing factors.
• The "ring syndrome" encompasses growth deficiency and is linked to ring instability.
• Familial transmission occurs, underscoring the need for prenatal diagnosis in at-risk pregnancies.