Mosaic trisomy 18 in a five-month-old infant

Area of Science:

• Genetics
• Pediatrics
• Clinical Medicine

Background:

• Mosaic trisomy 18 is a chromosomal abnormality where individuals possess both trisomy 18 and normal cell lines.
• Clinical manifestations are highly variable, ranging from mild to severe.
• This condition accounts for approximately 5% of all trisomy 18 cases.

Purpose of the Study:

• To describe a unique case of mosaic trisomy 18 in a five-month-old infant.
• To document previously undescribed dysmorphic features and cardiac abnormalities associated with this condition.
• To contribute to the understanding of the phenotypic spectrum and natural history of mosaic trisomy 18.

Main Methods:

• Clinical examination of a five-month-old infant presenting with vomiting and feeding difficulties.
• Detailed assessment of dysmorphic features, developmental delay, and hypotonia.
• Cytogenetic analysis of peripheral lymphocytes and skin fibroblasts to determine trisomy 18 levels.

Main Results:

• The infant presented with undernourishment, axial hypotonia, developmental delay, hypopigmentation, and craniofacial dysmorphies.
• A complex cardiac defect including atrial and ventricular septal defects, pulmonary artery stenosis, and a bicuspid aortic valve was identified.
• Cytogenetic analysis confirmed mosaic trisomy 18 with 90% trisomy in lymphocytes and 17% in fibroblasts.

Conclusions:

• This case expands the known phenotypic spectrum of mosaic trisomy 18.
• The described dysmorphic feature and cardiac abnormality represent novel findings for this condition.
• Further research is needed to fully elucidate the natural history and clinical variability of mosaic trisomy 18.