Developmental delay: global diagnostic approach — formative SAQs

SAQ 1 (10)

A corrected-age 26-month-old has ten single words, cannot combine words, stacks only one block, and walked at 20 months. There is no loss of skills. Newborn hearing screening showed refer/refer and diagnostic audiology was never completed. Examination is non-dysmorphic with normal tone. ^{[1] [5]}

1. Write a one-sentence problem representation and state why this is GDD rather than isolated speech delay. (3) ^[1]
2. List four mandatory or high-priority early actions that should not wait for a molecular result. (3) ^{[1] [5]}
3. Outline a modern aetiology testing approach, including how genetic testing eras inform your answer. (4) ^{[2] [3] [4] [6]}

Model answer

Problem representation. Corrected-age 26-month-old with significant delays in language, fine-motor and late gross-motor domains without regression — global developmental delay as a clinical pattern, not a final diagnosis. More than one domain is affected, so isolated speech delay is incorrect. ^[1]

Early actions. Complete diagnostic audiology and vision assessment; start early intervention/speech and OT pathways; take structured developmental–family–social history with interpreter if needed; safety-net for regression/seizures and book timely paediatric review. Do not wait for genetics to start supports. ^{[1] [5]}

Aetiology testing. Phenotype currently non-syndromic → agnostic genomic pathway per ACMG/AAP (exome/genome sequencing with CNV detection). Historical CMA-first cytogenetic era (Miller; Michelson evidence yields) still explains why karyotype alone is insufficient for unexplained GDD. Add metabolic/MRI/EEG only if red flags appear. Consent and genetics counselling in parallel. ^{[2] [3] [4] [6]}