A 15-year-old patient is referred to the physician by a teacher who is concerned about the patient's learning abilities and behavior. The patient's reading and writing skills are significantly impaired compared to other classmates, and the patient often misbehaves in class despite receiving numerous detentions. Neuropsychological assessment shows mild intellectual disability. Cytogenetic studies show a karyotype containing 47 chromosomes. Which of the following findings are most likely to be present on further evaluation?

Question

A 15-year-old patient is referred to the physician by a teacher who is concerned about the patient's learning abilities and behavior.  The patient's reading and writing skills are significantly impaired compared to other classmates, and the patient often misbehaves in class despite receiving numerous detentions.  Neuropsychological assessment shows mild intellectual disability.  Cytogenetic studies show a karyotype containing 47 chromosomes.  Which of the following findings are most likely to be present on further evaluation?

Quizplus · Accepted Answer

11ec160b_377f_659a_9249_899619365b37_MD0001_00 Klinefelter syndrome is most commonly caused by a meiotic nondisjunction event during parental gametogenesis that results in a 47,XXY karyotype. Variants include 46,XY/47,XXY mosaicism and 48,XXXY. In general, patients with higher numbers of X chromosomes are more likely to have more severe manifestations. The disorder is usually not diagnosed until puberty when the characteristic physical signs begin to develop. The major features are as follows: (Choice A) Arachnodactyly, scoliosis, and aortic root dilation are signs of Marfan syndrome, which occurs due to an inherited defect of the extracellular matrix protein fibrillin. (Choice B) Macroorchidism, large jaw, and intellectual disability are seen in patients with fragile X syndrome, an X-linked disorder caused by mutations in the fragile X mental retardation 1 gene. (Choice C) In females, loss of an X chromosome (45,XO karyotype) results in Turner syndrome, which presents with short stature, broad chest, and primary amenorrhea. (Choice D) Prader-Willi syndrome is characterized by short stature, hypotonia, intellectual disability, and obesity. The most common cause is a microdeletion affecting the paternal chromosome 15q11-13 critical region. Educational objective: 47,XXY is the most common genotype causing Klinefelter syndrome. Patients present with tall stature; small, firm testes; azoospermia; and gynecomastia. Mild intellectual disability is seen in some patients, and the severity generally increases with each additional X chromosome. __________ References: The cognitive phenotype in Klinefelter syndrome: a review of the literature including genetic and hormonal factors. (http://www.ncbi.nlm.nih.gov/pubmed/20014369)

A 15-Year-Old Patient Is Referred to the Physician by a Teacher