18q121

18q12.1 is a cytogenetic band on the long arm of chromosome 18 in humans. In ISCN nomenclature, 18q12.1 refers to a defined subregion at the distal part of 18q, used to describe chromosomal findings in karyotypes and genomic microarrays. The exact base-pair coordinates vary with the reference genome assembly, but the band lies within the q12 region of chromosome 18.

Genomic content: Like other cytogenetic bands, 18q12.1 spans multiple genes and regulatory elements. The specific genes present and their transcriptional activity depend on the genome build. CNVs (copy number variants) that remove or duplicate segments within 18q12.1 have been observed in population studies and clinical testing.

Clinical significance: Deletions or duplications that include 18q12.1 have been reported in individuals with a range of phenotypes, often including developmental delay, intellectual disability, motor abnormalities, and congenital anomalies. However, the clinical outcome depends on the size of the variant and which genes are affected; some alterations in 18q12.1 may have minimal or no discernible effect.

Diagnostic use: In clinical genetics, 18q12.1 is used to localize chromosomal imbalances detected by chromosomal microarray analysis or G-banded karyotyping. Detailed reporting typically specifies the exact coordinates or the affected genes.

See also: 18q- deletion syndrome; Chromosome 18; Copy number variation.