Archive Of Standardized Exam Questions: Duchenne Muscular Dystrophy (DMD)


This page is dedicated to organizing various examples of standardized exam questions whose answer is Duchenne muscular dystrophy (DMD). While this may seem a odd practice, it is useful to see multiple examples of how DMD 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.


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 DMD

Chief Complaints:

  • Muscle weakness is the classic chief complaint (it will be progressive).
  • Ambulatory difficulties: unable to walk due to weakness, cannot keep up with peers, clumsy gait.

Clinical Workup:

  • Gowers sign: patient uses hands/arms to aid themselves from getting up into standing position.
  • Hypertrophy of calf muscles: essentially pathognomonic on standardized exams.
  • Elevated creatine kinase can be detected on serum studies
  • Muscle biopsy can reveal loss of muscle tissues, regenerating muscle fibers, and fibrosis.

Question # 1

A 6 year old male comes to the pediatric clinic because he is being evaluated for progressive muscle weakness. The patient’s past medical history and family history is otherwise unremarkable. A physical exam reveals bilateral calf enlargement. When the patient is asked to stand from the seated position, he uses his hands to help push himself up to the standing position. A serum creatinine kinase is found to be 12,100 U/L. What is the likely diagnosis in this patient?

Explanation # 1

Muscle weakness + enlarged calfs + Gowers sign + elevated serum CK = DMD

Question # 2

A 4 year old male is brought to his pediatrician. His parents are concerned because he is unable to keep up with other children his age when they play outside. The boy stands up from the ground by squatting and then using his arms to help prop himself up into a standing position. A physical exam reveals calf muscles that appear larger then normal. What condition does this patient likely have?

Explanation # 2

Ambulatory difficulties + Gowers sign + enlarged calfs = DMD

Question # 3

A 11 year old male has recently lost the ability to walk. He also feels as though he is “too weak” to take a deep breath in or to “cough properly”. The patient’s calfs are noted to be larger then expected. What is the likely diagnosis in this patient?

Explanation # 3

Ambulatory difficulties + muscle weakness + enlarged calfs = DMD

Question # 4

A 3 year old male is noted to have a clumsy gait. He is found to have proximal muscle weakness, and calf hypertrophy on exam. Labs are conducted and this patina tis found to have an elevated creatine kinase value. A muscle biopsy is performed, and it shows the loss of muscle tissues, fibrosis, and regenerating muscle fibers. The patient has a maternal uncle who had similar findings and passed away when he turned 14. What is the likely diagnosis in this patient?

Explanation # 4

Clumsy gait + muscle weakness + calf hypertrophy + elevated creatine kinase + loss of muscle tissues/fibrosis/regenerating muscle fibers on muscle biopsy = DMD

Question # 5

A 4 year old male is brought to the clinic because he has been fatigued for the past 4 months. His mother has also noticed that he is clumsy when walking. The patient explains that he feels his “legs are very tired“. His past medical history is unremarkable. The patient has difficulty arising out of his chair during the physical exam, and uses his arms to support him out of the seated position. A physical exam is notable for hypertrophy of the calfs. What is the likely diagnosis?

Explanation # 5

Ambulatory difficulties + muscle weakness + Gowers sign + enlarged calfs = DMD

Question # 6

A 5 year old male is brought to the clinic because he has a 3 month history of progressive weakness. His mother explain that he has difficulty running, climbing trees, and standing up when he is sitting on the floor. He appears to have hypertrophy of his calf muscles, and his serum creatine kinase is elevated. What is the likely diagnosis in this patient?

Explanation # 6

Progressive weakness + enlarged calfs + elevated serum creatine kinase = DMD


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: A frameshift mutation on the dystrophin gene (DMD) causes a truncated protein to be translated which is the root cause of this genetic condition. Less commonly a nonsense mutation can lead to the formation of truncated/defective protein.
  • Location of mutation: X-chromsome p21.
  • Consequence of mutation: The dystrophin protein helps anchor muscle fibers (mainly in skeletal and cardiac muscles). It is responsible for connecting the intracellular cytoskeleton (actin) to transmembrane proteins of the extracellular matrix. The loss of functional dystrophin completely undermines this normal biological process, and leads to myonecrosis (death of muscles).
  • Inheritance pattern: X-lined recessive


  • Necrosis of heart and diaphragm muscles can be fatal.


  • What causes calfs to enlarge? The calf muscles do not increase with respect to muscle mass, rather the muscle is replaced with fibrofatty deposits that make them appear larger in size.



Page Updated: 04.19.2017