Variants of chromosome 9 with additional euchromatic bands: two case reports

Area of Science:

• Human Genetics
• Prenatal Diagnosis
• Cytogenetics

Background:

• Subtle chromosomal abnormalities can be challenging to detect prenatally.
• Maternally inherited variants require careful genetic counseling and characterization.

Purpose of the Study:

• To document and characterize two prenatal cases of maternally inherited chromosome 9 duplications.
• To investigate the nature and origin of these subtle genetic variations.

Main Methods:

• Cytogenetic analysis including G-banding and C-banding.
• Fluorescence in situ hybridization (FISH) using chromosome 9 specific probes and satellite heterochromatin probes.

Main Results:

• Two prenatal cases identified with maternally inherited duplications on chromosome 9.
• The extra bands were G-band positive, C-band negative, and FISH positive for chromosome 9 painting probes.
• FISH analysis excluded satellite heterochromatin, suggesting the duplicated segments are euchromatic.

Conclusions:

• The identified extra bands represent euchromatic segments of chromosome 9, likely duplications.
• These findings highlight the importance of advanced cytogenetic techniques for detecting subtle prenatal chromosomal variants.
• The study discusses potential mechanisms for the origin of these chromosome 9 variants.