Down-Turner Syndrome: A Case with Double Monoclonal Chromosomal Abnormality

Area of Science:

• Genetics
• Clinical Medicine
• Pediatrics

Background:

• Double aneuploidy, combining Down syndrome (trisomy 21) and Turner syndrome (monosomy X), is exceptionally rare.
• The occurrence of a double monoclonal chromosomal abnormality in such cases is even rarer.
• This case presents a unique instance of concurrent trisomy 21 and a ring X chromosome.

Purpose of the Study:

• To report a unique case of a double monoclonal chromosomal abnormality.
• To describe a patient with concurrent trisomy 21 and a ring X chromosome.
• To highlight the clinical presentation and diagnostic approach for this rare condition.

Main Methods:

• Clinical examination of a 28-month-old female with pathological short stature and dysmorphic features.
• Neonatal assessment including evaluation for generalized hypotonia and lymphedema.
• G-banded karyotype analysis of peripheral blood cells.

Main Results:

• The patient exhibited clinical features of both Down syndrome and Turner syndrome.
• Key features included pathological short stature (below -3 z-score), delayed psychomotor development, tilted upward palpebral fissures, short neck, brachycephaly, low-set ears, hypotonia, and lymphedema.
• Karyotype analysis revealed 47,X,r(X),+21 in all cells studied, confirming the double aneuploidy.

Conclusions:

• The coexistence of Down and Turner syndromes with a double monoclonal chromosomal abnormality is extremely rare.
• Clinical manifestations can be a combination of both syndromes, emphasizing the importance of recognizing specific features like persistent short stature and developmental delay.
• G-banded karyotype analysis is crucial for the definitive diagnosis of such complex chromosomal abnormalities.