This week, we are sharing another USMLE® Step 1-style practice question to test your knowledge of medical topics. Today’s case focuses on a 4-year-old-boy who was brought to the pediatrician for evaluation of unusual behavior. Can you figure it out?
A 4-year-old boy is brought to the pediatrician for evaluation of unusual behavior. His parents are concerned about his intellectual development and state that he is “quiet” and almost always by himself, both at home as well as in daycare. He plays with toy trains for hours daily. If the toys are misplaced, he becomes enraged and throws tantrums, which involve him banging his head against the wall. The patient was born full-term, and the pregnancy was uncomplicated. Weight and height are at the 55th percentile. During the examination, the patient does not make eye contact with the physician and sits in the corner playing with his toy trains. The physician attempts to take a train from the patient, which causes him to shout, cry, and flap both hands. The remainder of the physical examination is noncontributory. Which of the following is the most likely diagnosis?
A. Autism spectrum disorder
B. Rett Syndrome
C. Fetal alcohol spectrum disorder
D. Landau-Kleffner syndrome
E. Fragile X syndrome
F. Selective mutism
The correct answer to today’s USMLE® Step 1 Question is…
A. Autism spectrum disorder
Before we get to the Main Explanation, let’s look at the incorrect answer explanations. Skip to the bottom if you want to see the correct answer right away!
Incorrect answer explanations
The incorrect answers to today’s USMLE® Step 1 Question are…
B. Rett Syndrome
Incorrect: Rett syndrome is an X-linked dominant neurodevelopmental disorder that occurs almost exclusively in females. Affected patients initially develop normally, but then they gradually lose speech and motor capabilities typically around the age of 2.
C. Fetal alcohol spectrum disorder
Incorrect: Similar to children with autism spectrum disorder, children with fetal alcohol spectrum disorder (FASD) may have deficits in social and neurobehavioral skills. Children with FASD also have characteristic facial features, such as short palpebral fissures, a thin vermillion border, and a smooth philtrum. In contrast, these facial findings are absent in this patient.
D. Landau-Kleffner syndrome
Incorrect: Landau-Kleffner syndrome is an epileptic condition that presents with regression in language milestones after normal development. However, this patient does not have a history of seizures, and his clinical features are more suggestive of a different diagnosis.
E. Fragile X syndrome
Incorrect: Patients with Fragile X syndrome may display autism-like behaviors. However, patients with Fragile X syndrome will also typically have characteristic facial features including a long face, large ears, and a prominent jaw, all of which are absent in this patient.
F. Selective mutism
Incorrect: Selective mutism is characterized by intact communication skills in certain settings (e.g. home) but not in others (e.g. school). Additionally, restricted, repetitive behaviors, as seen in this patient, are typically absent in selective mutism.
Main Explanation
This patient presents with social isolation, repetitive stereotypical movements (e.g., hand flapping, headbanging), and a fixated interest in trains. He likely has autism spectrum disorder (ASD). ASD typically manifests within the first several years of life and is 4 times more common in males than in females.
ASD is a complex neurological disorder characterized by impaired social communication, restricted interests, and repetitive behaviors. Patients with ASD may exhibit findings described in the below table. In addition, these individuals often become distressed when their surrounding environment is changed due to limited adaptive capabilities. Children with ASD also have higher rates of co-occurring language problems, intellectual disabilities, and epilepsy than the general population.
Major Takeaway
Autism spectrum disorder should be suspected in children with impaired social communication, restricted interests, and repetitive behaviors. The condition is more common in males and is often diagnosed within the first few years of life.
References
Mughal, S., Faizy, R.M., Saadabadi, A. (2020) Autism spectrum disorder. StatPearls [Internet]. Web Address: https://www.ncbi.nlm.nih.gov/books/NBK525976/.
Yochum, A. (2016) Autism spectrum/pervasive developmental disorder. Primary Care. 43(2), 285-300. Doi: 10.1016/j.pop.2016.01.010.
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The United States Medical Licensing Examination (USMLE®) is a joint program of the Federation of State Medical Boards (FSMB®) and National Board of Medical Examiners (NBME®). Osmosis is not affiliated with NBME nor FSMB.
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