Milestones
A 24-month-old uses 15 single words, has no two-word phrases, and otherwise has normal motor development. What developmental domain is delayed, and what language milestone is expected by this age?
Language delay. By 24 months, children are expected to combine at least two words meaningfully; 15 single words is also concerning for limited vocabulary.
A child has deficits in social reciprocity and peer relationships but no demonstrated deficits in nonverbal communication. Does this establish DSM-5 Criterion A?
No. All three A subcriteria (A1, A2, A3) must be met.
Unlike Criterion B, which requires at least two of four subcriteria, Criterion A requires all three.
A 2-year-old has speech delay, inconsistent response to name, but good eye contact, joint attention, and imaginative play. What alternative diagnosis should be evaluated first?
Hearing impairment.
Preserved social reciprocity and pretend play with limited response to sound should prompt audiologic evaluation.
A toddler screens positive on the M-CHAT-R/F. What is the next step, and does this result establish ASD?
Follow the indicated follow-up/referral pathway for comprehensive developmental evaluation and early intervention; no, it is a screening result.
A 30-month-old has language regression and suspected ASD but has not yet received a formal diagnosis. Should early intervention be delayed?
No. Refer for developmental evaluation and early intervention based on identified concerns.
An 18-month-old walks independently, uses a spoon, and follows simple commands but has no meaningful words. Which developmental domain is primarily affected?
Expressive language
A child has poor eye contact, difficulty understanding gestures, and limited facial expression during social interactions. Which DSM-5 criterion is most directly represented?
Criterion A2: deficits in nonverbal communicative behaviors used for social interaction.
A2 includes eye contact, gestures, facial expressions, and integration of verbal/nonverbal communication.
A girl develops typically until 12–18 months, then loses purposeful hand use and develops repetitive hand-wringing with slowing head growth. What syndrome is most likely?
Rett syndrome.
Classic features include developmental regression, hand stereotypies, and acquired microcephaly; MECP2 variants are commonly implicated.
A boy with suspected ASD has a normal chromosomal microarray. Which important genetic condition is not excluded because it requires repeat-expansion testing?
Fragile X syndrome (FMR1 CGG-repeat expansion).
Microarray detects copy-number changes, not the FMR1 repeat expansion.
An autistic child has severe irritability with dangerous aggression despite appropriate behavioral and environmental interventions. Which two medications have FDA approval for ASD-associated irritability in specified pediatric age groups?
Risperidone and aripiprazole.
These medications treat irritability, not the core diagnostic features of ASD; age eligibility and adverse effects matter.
A 30-month-old previously used 40 words but now uses 20. What is the term for this finding, and what makes it more concerning than simply having a small vocabulary?
Language regression; loss of previously acquired skills.
A child lines up toys, becomes distressed when the arrangement changes, and has extreme sensitivity to clothing textures. Which DSM-5 B criteria are supported?
B1 (repetitive use of objects), B2 (insistence on sameness), and B4 (sensory reactivity).
These observations can support multiple B criteria, but clinical context determines whether behaviors are atypical in intensity or impact.
A boy has developmental delay, social communication difficulties, prominent ears, an elongated face, and a family history of intellectual disability. What diagnosis should be considered?
Fragile X syndrome.
Fragile X may produce ASD-associated features alongside characteristic physical findings and intellectual disability.
A child with ASD has marked macrocephaly and multiple hamartomatous lesions. Which gene should be evaluated, and what signaling pathway is dysregulated?
PTEN; increased PI3K–AKT–mTOR signaling.
PTEN is a tumor suppressor that negatively regulates the pathway.
An autistic child receiving risperidone develops weight gain, increased prolactin, and extrapyramidal symptoms. Which receptor actions explain its therapeutic and adverse effects?
D2 and 5-HT2A receptor antagonism; D2 blockade contributes to hyperprolactinemia and extrapyramidal effects.
A 3-year-old speaks in short sentences but rarely engages in pretend play or reciprocal interaction with peers. Which developmental domain is disproportionately impaired?
Social communication / social development.
A 6-year-old has marked social communication deficits but no current repetitive behaviors. Parents describe intense fixated interests and rigid routines at age 3. Can DSM-5 Criterion B still be met?
Yes, if at least two B features are established currently or by history.
DSM-5 allows restricted/repetitive behaviors to be present currently or historically.
A child with social withdrawal, language delay, abdominal pain, and a history of pica lives in a pre-1978 home with peeling paint. What potentially treatable exposure must be investigated?
Lead exposure / lead poisoning.
A venous blood lead level is indicated with relevant exposure risk or pica.
A child has hypomelanotic macules, seizures, cortical tubers, and autistic features. Which genes are implicated, and what cellular pathway becomes overactive?
TSC1 or TSC2; mTORC1 signaling.
Loss of hamartin/tuberin function removes inhibition of mTORC1.
A preschooler with ASD has persistent sleep-onset difficulties. What is the preferred initial approach before considering medication?
Assess contributors and use behavioral sleep interventions: consistent bedtime routine, sleep schedule, and environmental adjustments.
Evaluate sleep-disordered breathing, anxiety, sensory needs, and other possible contributors.
A toddler has delayed expressive language but normal hearing. What additional developmental findings would most strongly suggest ASD rather than isolated expressive language disorder?
Persistent social reciprocity/nonverbal communication deficits plus restricted or repetitive behaviors.
A child has profound intellectual disability and limited speech. What additional evidence is needed to diagnose co-occurring ASD?
Social communication must be below what is expected for the child's general developmental level, with the required restricted/repetitive behavior criteria.
A 4-year-old has social communication deficits but no restricted/repetitive behaviors, sensory abnormalities, or history of rigid routines. Which diagnosis may better fit than ASD?
Social (pragmatic) communication disorder.
This condition involves pragmatic communication difficulties without the restricted/repetitive behavior domain required for ASD.
A 30-month-old has ASD features but a normal neurologic examination and no seizures. Is brain MRI routinely indicated to establish the diagnosis? What finding would change your answer?
No. MRI is not routine for ASD; focal neurologic abnormalities, seizures, or atypical regression may justify imaging.
A child with ASD has limited spoken language but demonstrates an ability to communicate through pictures. What intervention can support functional communication without waiting for speech to develop?
Augmentative and alternative communication (AAC), such as picture-based communication or a speech-generating device.