A 2-year-old male is brought to the physician due to mental retardation. Physical examination reveals a single palmar crease, flat face and prominent epicanthal folds. The most likely cause of these…

The correct answer is C. meiotic nondisjunction. This patient with a flat face, mental retardation, prominent epicanthal folds and a single palmar crease most likely has trisomy 21 also called Down syndrome. It is the most common cause of genetic intellectual disability. Other findings in patients with trisomy 21 include…

Abnormal Processes

Question

A 2-year-old male is brought to the physician due to mental retardation. Physical examination reveals a single palmar crease, flat face and prominent epicanthal folds. The most likely cause of these findings is:

Options

Aheteroplasmy
Bincomplete penetrance
Cmeiotic nondisjunction
Dmosaicism
ERobertsonian translocation

How the community answered

(29 responses)

A
3% (1)
C
83% (24)
D
10% (3)
E
3% (1)

Explanation

This patient with a flat face, mental retardation, prominent epicanthal folds and a single palmar crease most likely has trisomy 21 also called Down syndrome. It is the most common cause of genetic intellectual disability. Other findings in patients with trisomy 21 include duodenal atresia, Hirsch sprung disease, atrioventricular septal defects, Brush field spots and early onset Alzheimer disease. The most common cause of Down syndrome is meiotic nondisjunction in older pregnant females. A few cases of Down syndrome are caused by unbalanced Robertsonian translocations mostly between chromosomes 14 and 21 and only 1% of cases are due to post- fertilization mitotic errors. Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division. Meiotic nondisjunction is implicated in 95% of Down syndrome cases.

Topics

#Down syndrome#trisomy 21#meiotic nondisjunction#chromosomal disorders

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