Archive Of Standardized Exam Questions: Achondroplasia (Dwarfism)

OVERVIEW

This page is dedicated to organizing various examples of standardized exam questions whose topic is achondroplasia (dwarfism). While this may seem a odd practice, it is useful to see multiple examples of how achondroplasia will be characterized on standardized exams (namely the boards and the shelf exams). This page is not meant to be used as a traditional question bank (as all of the answers will be the same), however seeing the classic “test” characterization for a topic is quite valuable.

KEY CHARACTERISTICS OF THIS CONDITION (ON EXAMS)

When it comes to standardized exams, each topic 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 achondroplasia. 

  • Physical features:
    • Short stature
    • Frontal bossing: bulging forehead
    • Short limbs + normal toros 
  • Inheritance pattern: autosomal dominant
QUESTION EXAMPLES

Question # 1

A 25 year old woman comes to the clinic for a routine visit. She is 3ft 10 in tall, and has short extremities. Her torso length is within normal limits. Her physical exam is notable for depression of the nasal bridge, and a bulging forehead. The patient’s husband has none of these physical findings and is 5ft 10 in in height. The patient is counseled that she has a 50% chance of passing on her condition to her children. What condition does she have?

Explanation # 1

Short stature + bulging forehead + long limbs/normal torso + autosomal dominant inheritance pattern = achondroplasia

Question # 2

A 30 year old male comes to the clinic for family planning. He is 3ft 8 in tall. His limbs are disproportionately shorter in length compared to his torso. He also has a prominent forehead. His wife is of average height and has no remarkable features. They are deciding on conceiving children soon. What condition might the father have that could affect their decision to conceive?

Explanation # 2

Short stature + bulging forehead + long limbs/normal torso = achondroplasia

Question # 3

 

Explanation # 3

Short stature + bulging forehead + long limbs/normal torso + autosomal dominant inheritance pattern = achondroplasia

TESTABLE FACTS ABOUT THIS TOPIC (BEYOND ITS IDENTIFICATION)

Many questions on standardized exams go beyond simply recognizing the underlying topic. Often there are specific testable facts regarding some aspect of the topic’s pathophysiology/management/clinical implications that are commonly asked. Some of these are listed below:

  • Cause:
    • Sporadic mutation (most of the time): thought to be caused by advanced paternal age in most cases.
    • Mutated gene: fibroblast growth factor receptor 3 (FGFR3)
    • Type of mutation: gain of function.
    • Inheritance pattern: autosomal dominant.
    • Consequence: inhibition of chondrocyte proliferation (hence the name)

 

 

Page Updated: 05.07.2017