Complex small supernumerary marker chromosome with a 15q/16p duplication: clinical implications

Area of Science:

• Genetics
• Human Genetics
• Molecular Cytogenetics

Background:

• Complex small supernumerary marker chromosomes (sSMCs) are associated with reproductive issues and congenital abnormalities.
• Chromosome 15 is frequently involved in rearrangements and sSMC formation.
• The 16p11.2 region is known to be susceptible to rearrangements, with described copy number variations (CNVs).

Observation:

• A 6-year-old girl presented with a complex sSMC resulting in concomitant partial trisomy 15q and 16p.
• Karyotype analysis, including G/C banding, FISH, and SNP array, defined the sSMC as 47,XX,+der(15)t(15;16)(q13;p13.2)mat.
• The sSMC was maternally inherited and had been passed down through several generations.

Findings:

• The patient exhibited a phenotype including microsomia, intellectual disability, speech delay, hearing impairment, and dysphagia.
• The sSMC contained material from both chromosomes 15 and 16.
• This represents the first reported instance of concurrent partial trisomy 15q and 16p.

Implications:

• The diverse phenotypes associated with complex sSMCs pose challenges for genotype-phenotype correlation.
• Accurate clinical assessment and genetic counseling for patients with sSMCs are crucial.
• Further research is needed to understand the full spectrum of clinical outcomes for such complex chromosomal rearrangements.