Duplication of 7p21.2-->pter due to maternal 7p;21q translocation: implications for critical segment assignment in...

Area of Science:

• Genetics
• Clinical Medicine
• Cytogenetics

Background:

• Genetic translocations can lead to unbalanced karyotypes, resulting in partial duplications or deletions of chromosomal material.
• 7p duplication syndrome is a rare genetic disorder characterized by intellectual disability and specific facial dysmorphisms.

Observation:

• A 1-year-old boy presented with global developmental delay, intellectual disability, and distinctive facial features including ocular hypertelorism, a low nasal bridge, and a small mandible.
• Cytogenetic analysis revealed an unbalanced karyotype (46,XY,add(21)(q22.3)) resulting from a maternal balanced translocation between chromosomes 7 and 21.
• Fluorescence in situ hybridization (FISH) confirmed the additional material on chromosome 21q originated from chromosome 7, specifically identifying an unbalanced translocation der(21)t(7;21)(p21.2;q22.3)mat.

Findings:

• The patient's karyotype indicated a duplication of the distal region of chromosome 7p.
• The observed phenotype in the patient closely resembles previously reported cases of 7p duplication syndrome.
• The findings suggest that the critical region responsible for the characteristic features of 7p duplication syndrome is located at 7p21.2 or a more proximal segment.

Implications:

• This case contributes to the understanding of the genotype-phenotype correlation in 7p duplication syndrome.
• Identifying the critical segment at 7p21.2 provides valuable information for genetic counseling and diagnosis of similar cases.
• Further research into the specific genes within the 7p21.2 region may elucidate the molecular mechanisms underlying the syndrome's features.