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]

SAQ 2 (10)

A 4-year-old from a consanguineous family has progressive multi-domain delay, intermittent vomiting with intercurrent illness, and new abnormal movements. Parents want “only a speech therapist.” [1] [6]

1. Which red flags reclassify this away from routine static GDD? (3) [1]
2. What investigation categories become higher yield and why? (3) [1] [6]
3. How do you communicate a plan that both investigates urgently and supports the family without blame? (4) [1] [5]

Model answer

Red flags. Progressive course, decompensation with illness, abnormal movements, consanguinity with multi-domain delay — possible neurometabolic/genetic progressive disease rather than mild static GDD. [1]

Investigations. Expedited genetics (including genomic sequencing strategies), selective metabolic testing guided by red flags, neurology review; imaging/EEG if examination or spells indicate. Therapy still starts, but aetiology work-up is accelerated. [1] [6]

Communication. Name concern in plain language: skills are behind and the progressive features mean we look harder for treatable and genetic causes now. Offer supports today, explain tests and consent, use teach-back, avoid blaming consanguinity, and safety-net encephalopathy/seizures. [1] [5]