Patient with trisomy 6 mosaicism

Area of Science:

• Genetics
• Prenatal Diagnosis
• Developmental Biology

Background:

• Prenatal diagnosis often involves analyzing chorionic villi for chromosomal abnormalities.
• Trisomy 6 is a rare chromosomal condition with limited data on liveborn outcomes.
• Mosaicism, the presence of two or more cell lines with different genotypes, can complicate diagnosis and prognosis.

Observation:

• A pregnancy with a growth-restricted fetus and increased nuchal translucency at 12 weeks gestation showed trisomy 6 in chorionic villi.
• The infant was born prematurely with multiple congenital anomalies, including cardiac defects and limb malformations.
• Trisomy 6 was not detected in peripheral blood lymphocytes but was confirmed in umbilical cord fibroblasts.

Findings:

• Postnatal cytogenetic analysis confirmed trisomy 6 mosaicism in fibroblasts from umbilical cord and skin.
• The child, despite growth delay, exhibited relatively normal neurodevelopment by 2.75 years of age.
• Papular erythema, suggestive of epidermal nevi, appeared around age two, with mosaic trisomy 6 confirmed in skin fibroblasts.

Implications:

• This case highlights the importance of considering trisomy 6 mosaicism in prenatal diagnoses, especially with fetal growth restriction and nuchal translucency.
• It demonstrates that liveborn infants with trisomy 6 mosaicism can have variable outcomes, with potential for relatively normal development.
• Further research is needed to understand the long-term prognosis and phenotypic spectrum of trisomy 6 mosaicism.