Trisomy 2q11.2-->q21.1 resulting from an unbalanced insertion in two generations

Area of Science:

• Genetics
• Human Genetics
• Chromosomal Abnormalities

Background:

• Partial autosomal trisomies can arise from complex chromosomal rearrangements.
• Interchromosomal insertions are a known mechanism leading to unbalanced karyotypes.
• Understanding the inheritance patterns of trisomies is crucial for genetic counseling.

Observation:

• Two cases of proximal 2q trisomy (2q11.2-->q21.1) were identified, resulting from an interchromosomal insertion.
• Fluorescence in situ hybridization confirmed the chromosomal origin of the insertion.
• An unbalanced karyotype (46,XX,der(8),ins(8;2)(p21.3;q21.1q11.2)) was observed in both the proband and her mother.

Findings:

• The affected individuals exhibited mild mental retardation, short stature, dysmorphic features, insulin-dependent diabetes mellitus, and psychotic illness.
• This represents a rare instance of direct transmission of a partial autosomal trisomy within a family.
• The specific chromosomal rearrangement, ins(8;2)(p21.3;q21.1q11.2), is associated with a distinct phenotype.

Implications:

• This case highlights the phenotypic variability associated with proximal 2q trisomy.
• Direct transmission of such unbalanced rearrangements underscores the importance of detailed family genetic studies.
• Further research into the specific genes within the duplicated 2q region may elucidate the underlying mechanisms of the observed clinical features.