A mother brings her 3-year-old son to the doctor because she is worried that he might be harming himself by constantly banging his head on the wall. He has been exhibiting this behavior for a few months. She is also worried because he has started to speak less than he used to and does not respond when his name is called. He seems aloof during playtime with other children and seems to have lost interest in most of his toys. What is the most likely diagnosis?

Attention deficit hyperactivity disorder

A two-year-old female presents to the pediatrician with her mother for a routine well-child visit. Her mother is concerned that the patient is a picky eater and refuses to eat vegetables. She drinks milk with meals and has juice sparingly. She goes to sleep easily at night and usually sleeps for 11-12 hours. The patient has trouble falling asleep for naps but does nap for 1-2 hours a few times per week. She is doing well in daycare and enjoys parallel play with the other children. Her mother reports that she can walk down stairs with both feet on each step. She has a vocabulary of 10-25 words that she uses in the form of one-word commands. She is in the 42nd percentile for height and 48th percentile for weight, which is consistent with her growth curves. On physical exam, she appears well nourished. She can copy a line and throw a ball. She can follow the command to “give me the ball and then close the door.” This child is meeting her developmental milestones in all but which of the following categories?

Social and receptive language skills

This child is developmentally normal

A 4-year-old boy is brought to the physician because of non-fluent speech. His mother worries that his vocabulary is limited for his age and because he cannot use simple sentences to communicate. She says he enjoys playing with his peers and parents, but he has always lagged behind in his speaking and communication. His speech is frequently not understood by strangers. He physically appears normal. His height and weight are within the normal range for his age. He responds to his name, makes eye contact, and enjoys the company of his mother. Which of the following is the most appropriate next step in management?

Evaluate response to methylphenidate

A 3-year-old boy is brought in by his mother because she is concerned that he has been “acting differently recently”. She says he no longer seems interested in playing with his friends from preschool, and she has noticed that he has stopped making eye contact with others. In addition, she says he flaps his hands when excited or angry and only seems to enjoy playing with objects that he can place in rows or rigid patterns. Despite these behaviors, he is meeting his language goals for his age (single word use). The patient has no significant past medical history. He is at the 90th percentile for height and weight for his age. He is afebrile and his vital signs are within normal limits. A physical examination is unremarkable. Which of the following is the most likely diagnosis in this patient?

Pervasive developmental disorder, not otherwise specified

Childhood disintegrative disorder

A 3-year-old boy is brought to your pediatrics office by his parents for a well-child checkup. The parents are Amish and this is the first time their child has seen a doctor. His medical history is unknown, and he was born at 39 weeks gestation. His temperature is 98.3°F (36.8°C), blood pressure is 97/58 mmHg, pulse is 90/min, respirations are 23/min, and oxygen saturation is 99% on room air. The child is in the corner stacking blocks. He does not look the physician in the eye nor answer your questions. He continually tries to return to the blocks and becomes very upset when you move the blocks back to their storage space. The parents state that the child has not begun to speak and often exhibits similar behaviors with toy blocks he has at home. On occasion, they have observed him biting his elbows. Which of the following is the best next step in management?

Educating the parents about autism spectrum disorder

Restructuring of the home environment

A 4-year-old girl is brought to the pediatrician by her parents after her mother recently noticed that other girls of similar age talk much more than her daughter. Her mother reports that her language development has been abnormal and she was able to use only 5–6 words at the age of 2 years. Detailed history reveals that she has never used her index finger to indicate her interest in something. She does not enjoy going to birthday parties and does not play with other children in her neighborhood. The mother reports that her favorite “game” is to repetitively flex and extend the neck of a doll, which she always keeps with her. She is sensitive to loud sounds and starts screaming excessively when exposed to them. There is no history of delayed motor development, seizures, or any other major illness; perinatal history is normal. When she enters the doctor’s office, the doctor observes that she does not look at him. When he gently calls her by her name, she does not respond to him and continues to look at her doll. When the doctor asks her to look at a toy on his table by pointing a finger at the toy, she looks at neither his finger nor the toy. The doctor also notes that she keeps rocking her body while in the office. Which of the following is an epidemiological characteristic of the condition the girl is suffering from?

This condition is 4 times more common in boys than girls.

There has been a steady decline in prevalence in the United States over the last decade.

There is an increased risk if the mother smoked during pregnancy.

There is an increased risk with low prenatal maternal serum vitamin D level.

There is an increased incidence if the mother gives birth before 25 years of age.

A 9-year-old boy is brought to a pediatric psychologist by his mother because of poor academic performance. The patient’s mother mentions that his academic performance was excellent in kindergarten and first grade, but his second and third-grade teachers complain that he is extremely talkative, does not complete schoolwork, and frequently makes careless mistakes. They also complain that he frequently looks at other students or outside the window during the class and is often lost during the lessons. At home, he is very talkative and disorganized. When the pediatrician asks the boy his name, he replies promptly. He was born at full term by spontaneous vaginal delivery. He is up-to-date on all vaccinations and has met all developmental milestones on time. A recent IQ test scored him at 95. His physical examination is completely normal. When he is asked to read from an age-appropriate children’s book, he reads it fluently and correctly. Which of the following is the most likely diagnosis in this patient?

Attention-deficit/hyperactivity disorder

Early intervention in ASD for USMLE Step 2 CK: High-Yield Psychiatry Lessons

Core Principles - The Early Bird Advantage

Neuroplasticity: Capitalizes on the brain's high malleability in early childhood (ideally < 3 years old) to rewire neural circuits and improve developmental trajectory.
Core Deficit Targeting: Focuses on improving social communication, joint attention, and play skills while reducing restrictive/repetitive behaviors.
Key Modalities:
- Applied Behavior Analysis (ABA): Uses reinforcement to teach new skills.
- Developmental Models (e.g., ESDM): Relationship-based, integrated into natural routines.
Intensity & Duration: Evidence supports intensive intervention, often ≥25 hours/week.
Parent/Caregiver Training: Essential for skill generalization.

⭐ Early intensive behavioral intervention (EIBI) can lead to significant gains in IQ, language, and adaptive behavior, with some children achieving functioning within the normal range.

Human Brain Development: Neural Connections by Function

Screening & Diagnosis - Finding the Flags

Universal Screening: All children screened at 18 and 24 months.
- Tool: M-CHAT-R/F (Modified Checklist for Autism in Toddlers, Revised with Follow-up).
Comprehensive Evaluation: Triggered by positive screen or clinical concern.
- Gold Standard Tools:
  - ADOS-2: Autism Diagnostic Observation Schedule (direct child assessment).
  - ADI-R: Autism Diagnostic Interview-Revised (structured parent interview).

⭐ Regression of milestones (e.g., loss of language or social skills) at any age is a critical red flag warranting immediate, comprehensive evaluation for ASD.

Intervention Models - The Therapy Toolkit

Applied Behavior Analysis (ABA): The most established model. Uses reinforcement principles to ↑ desired behaviors & ↓ challenging ones.
- Discrete Trial Training (DTT): Structured, one-on-one instruction.
- Pivotal Response Training (PRT): More naturalistic, targets core developmental areas.
Early Start Denver Model (ESDM): Comprehensive, play-based approach for children 12-48 months. Integrates ABA principles with developmental and relationship-based methods.
DIR/Floortime Model: Focuses on emotional development and relationships. Therapists and parents engage with the child based on their interests to promote connection and development.
Core Ancillary Therapies:
- Speech-Language Therapy (SLT): Targets verbal and non-verbal communication.
- Occupational Therapy (OT): Addresses sensory processing issues and activities of daily living (ADLs).

⭐ Exam Favorite: Early and intensive intervention (≥25 hours/week) is the strongest predictor of positive long-term outcomes, more so than the specific therapeutic model chosen.

4 Factors in ABA Therapy Success

High-Yield Points - ⚡ Biggest Takeaways

Early diagnosis of ASD, ideally before age 2, is crucial for improving long-term outcomes.

Applied Behavior Analysis (ABA) is the most well-established, evidence-based behavioral intervention.

Key goals are improving social communication and reducing restrictive/repetitive behaviors.

A multidisciplinary team (speech, occupational therapy) is the standard of care.

Parental involvement is critical for generalizing skills and improving prognosis.

Medications target co-occurring conditions (e.g., ADHD, aggression), not core ASD symptoms.

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