Isochromosome 18p in a mother and her child

Area of Science:

• Genetics
• Clinical Genetics
• Human Genetics

Background:

• Isochromosome 18p [i(18p)] is a rare chromosomal abnormality.
• Tetrasomy 18p syndrome results from having four copies of the short arm of chromosome 18.
• Familial cases of supernumerary i(18p) are infrequently documented.

Purpose of the Study:

• To report a unique familial case of isochromosome 18p.
• To describe the clinical manifestations in a mother with mosaic i(18p) and her child with full tetrasomy 18p.
• To highlight the first documented instance of adult mosaicism for i(18p) with associated clinical features.

Main Methods:

• Karyotyping was performed on the mother and child to identify chromosomal abnormalities.
• Clinical examinations were conducted to assess the phenotypic features of both individuals.
• Genetic counseling and family history were integral to the case assessment.

Main Results:

• The mother was diagnosed with mosaic isochromosome 18p, exhibiting partial tetrasomy 18p syndrome.
• The child inherited the isochromosome 18p from the mother, presenting with full tetrasomy 18p syndrome.
• This represents the first reported case of mosaic i(18p) in an adult patient presenting with clinical manifestations.

Conclusions:

• Familial transmission of supernumerary isochromosome 18p can occur, leading to varying degrees of tetrasomy 18p syndrome.
• Mosaicism for i(18p) in adults can present with distinct clinical features, expanding the known spectrum of the syndrome.
• This case underscores the importance of genetic analysis in familial chromosomal abnormalities and the phenotypic variability of tetrasomy 18p.