This page is dedicated to organizing various examples of standardized exam questions whose answer is fragile X syndrome. While this may seem a odd practice, it is useful to see multiple examples of how fragile X syndrome. will be characterized on standardized exams (namely the boards and the shelf exams). This page is not meant to be used as a tradition question bank (as all of the answers will be the same), however seeing the classic “test” characterization for a disease is quite valuable.
KEY CHARACTERISTICS OF THIS CONDITION (ON EXAMS)
When it comes to standardized exams, each condition has its own “code” marked by key buzzwords, lab findings, clues, etc. If you are well versed in this code you will be able to more quickly identify the condition that is being discussed, and get the right answer on the exam you are taking. Below is the “code” for fragile X syndrome..
- Developmental delay: issues with reading, speaking, comprehension
- Academic performance issues: issues with school performance
- Intellectual disability: patients might have a formal diagnosis
- Abnormal facial features: large/prominent ears, long face, prominent jaw, large forehead
- Macroorchidism: large testicles are very specific to this condition
- Low IQ: can be revealed on formal testing
- Trinucleotide repeats on X chromosome: CGG repeats will be present here
Question # 1
A 7 year old boy is brought to the clinic for evaluation due to his difficulties reading. His teacher has reported in parent-teacher conferences that the child is unable to keep up with the rest of the class. His mother explains that generally he is very well behaved, but he does have the odd tendency of flapping his hands when he gets nervous. Physical exam shows a high forehead, prominent supraorbital ridges, protruding ears, and a prominent jaw. Formal testing shows that the patient has an IQ of 69, which appears consistent with his academic performance. What is the most likely diagnosis that can explain these findings?
Explanation # 1
Abnormal facial features (protruding ears) + low IQ = fragile X syndrome
Question # 2
An 11 year old male with intellectual disability is brought to the pediatrician for a routine checkup. The patient was adopted as a child, and much of his past medical history is unknown. His immunizations are currently up to date, and he has no recorded allergies. A physical exam reveals multiple findings including large ears, a long face, and macroorchidism. What is the likely diagnosis in this patient?
Explanation # 2
Intellectual disability + abnormal facial features (large ears) + macroorchidism = fragile X syndrome
Question # 3
A 4 year old male is brought to the pediatric clinic in order to follow up on his speech delay and intellectual disability. The patient has a limited vocabulary, and does not combine the words he knows into longer phrases. A hearing test is performed and is unremarkable. Laboratory testing shows 300 CGG trinucleotide repeats that are present on the X chromosome. What is the likely diagnosis in this patient?
Explanation # 3
Intellectual disability + CGG repeats on X chromosome = fragile X syndrome
Question # 4
A 13 year old male is brought to the clinic because he has been having academic issues at school. His performance has deteriorated to the point that now he is failing his current grade. His parents explain that he is very hyperactive at home and school, and that he has begun to interfere with the learning of other students. A physical exam reveals a high forehead, and long protruding ears. Sexual development is a Tanner stage 5, and the patient has macroorchidism. Formal testing reveals an IQ of 68. What is the likely diagnosis in this patient?
Explanation # 4
Abnormal facial features (long protruding ears) + macroorchidism + low IQ = fragile X syndrome
Question # 5
A 3 year old male is brought to the clinic because he has not yet begun to speak. His past medical history is unremarkable, and he has received all of the appropriate immunizations so far. His family history is notable for an older brother who has intellectual disability. A physical exam reveals a high forehead, prominent ears, and a long face. The physician also notices psychomotor activity while performing the history and physical. What is the likely diagnosis in this patient?
Explanation # 5
Developmental delay (not speaking) + abnormal facial features (prominent ears) = fragile X syndrome
TESTABLE FACTS ABOUT THIS CONDITION (BEYOND ITS IDENTIFICATION)
Many questions on standardized exams go beyond simply recognizing the underlying condition. Often there are specific testable facts regarding some aspect of the disease’s pathophysiology/management/clinical implications that are commonly asked. Some of these are listed below:
- Affected gene: FMR1 (on X-chromosome)
- Exact defect: Unstable expansion of trinucleotide repeat (CGG)
- Origin of name: when cells with this defect are culture in folate deficient medium, the area of the trip-nucleotide repeat does not stain on cytogenic studies and appears “broken” (giving the name of “Fragile-X”)
Page Updated: 09.18.2016