Partial 1q and 21p trisomies in a male child due to maternal t(1;21)

Area of Science:

• Genetics
• Cytogenetics
• Human Genetics

Background:

• Cytogenetic investigations are crucial for diagnosing chromosomal abnormalities.
• Translocations, particularly Robertsonian translocations, can lead to aneuploidy and genetic disorders.
• Maternal inheritance of chromosomal rearrangements requires careful genetic counseling.

Observation:

• A 7-year-old male proband presented for cytogenetic analysis.
• Karyotype analysis revealed an extra derivative chromosome 21.
• The specific chromosomal rearrangement identified was a reciprocal translocation between chromosomes 1 and 21, denoted as t(1;21)(q32;q11).

Findings:

• The proband's karyotype was determined to be 47, XY + der(21), t(1;21)(q32;q11)mat.
• This indicates trisomy 21 due to a translocation, specifically an unbalanced Robertsonian translocation.
• The translocation was confirmed to be of maternal origin (mat).

Implications:

• This genetic finding explains the proband's condition, likely Down syndrome, and highlights the importance of parental origin in chromosomal abnormalities.
• Understanding the specific translocation is vital for accurate genetic counseling regarding recurrence risks and family planning.
• Further research into the phenotypic impact of this specific t(1;21) translocation can refine clinical management and understanding of Down syndrome variations.