Definition

• The domains are gross and fine motor, speech and language (receptive and expressive), cognition or problem-solving, social and personal, and activities of daily living (adaptive). - Textbook of Family Medicine 9e, "Evaluation of Developmental Delay"
• A common working definition is a developmental quotient (DQ) below 70% in two or more domains in a child younger than 5-6 years. - Bradley and Daroff's Neurology in Clinical Practice, Ch. 8, p. 107
• DQ = developmental age ÷ chronological age, calculated for each domain separately.
• GDD is a provisional label. Children under 5 are hard to test reliably. If the delay persists after age 5, it is usually re-labelled as intellectual disability.
• Delay can affect one domain or several. GDD means several. - The Harriet Lane Handbook, 23rd ed.

How a typical case presents

• Parents or a screening tool flag late milestones, for example late sitting or walking, little speech, or poor social interaction.
• Some children also have hypotonia, seizures, microcephaly, dysmorphic features, or regression.

Approach to a case

• Record the pattern and timing of milestones in each domain.
• Screening tools include ASQ, PEDS, Ireton CDI and M-CHAT. Confirm with formal testing by a developmental specialist or psychologist.
• Regression is a red flag. Loss of skills suggests a neurodegenerative or metabolic disease or Rett syndrome, and needs urgent work-up.

• Ask about prenatal, birth and perinatal events (prematurity, hypoxic-ischaemic injury, infections, alcohol or drug exposure) and about newborn screening.
• Ask about family history, consanguinity, and unexplained deaths.
• Measure head circumference, growth, and look for dysmorphism and skin markers.
• Do a full neurological examination, plus vision and hearing.

• Hearing screen: formal audiology is indicated for all children with GDD. - The Harriet Lane Handbook, 23rd ed.
• Chromosomal microarray (CMA): this is first-line, with the highest yield of any single test (about 8-12%).
• Fragile X testing: do this in every child with nonspecific GDD, whatever their sex, because CMA misses trinucleotide repeats.
• Targeted genetic tests: use methylation testing for Angelman or Prader-Willi syndrome and MECP2 testing for Rett syndrome when the phenotype suggests them. Karyotype can follow a normal CMA.
• Metabolic tests: the yield is low (<1%) in nonspecific GDD. Test selectively if there is:
  • metabolic decompensation
  • consanguinity
  • an affected relative
  • neonatal seizures
  • coarse facies
  • hypotonia
  • organomegaly
  • Selective tests include CBC, metabolic panel, lactate, plasma amino acids, CK, urine organic acids, and creatine metabolites.
• MRI brain: do this first-line if there are focal neurological signs. Otherwise it can be second-line, since sedation carries some risk. Also do it for microcephaly or macrocephaly, regression, or seizures.
• EEG: do this if seizures are suspected or there is regression.
• Other: check thyroid function, lead level, and iron studies where relevant. Screen for autism.

Management

• Early intervention: physiotherapy, occupational therapy, speech therapy, and special education. Start as soon as delay is identified, without waiting for a diagnosis.
• Treat any identified cause, such as hypothyroidism, a metabolic disorder, or epilepsy.
• Manage comorbidities: vision, hearing, feeding, seizures, behavioural problems and sleep.
• Give genetic counselling to the family.
• Follow up with serial developmental reassessment.

Common causes

• Genetic: Down syndrome, fragile X, Rett, Angelman.
• Perinatal: prematurity, birth asphyxia, kernicterus, neonatal infection.
• Metabolic or endocrine: congenital hypothyroidism, inborn errors of metabolism.
• Structural brain malformations.
• Environmental: neglect or deprivation, fetal alcohol exposure, lead.
• Sensory impairment: hearing or vision loss.

Recent evidence

Steps

1. Write down the date of assessment (today) as year, month, day.
2. Write down the date of birth (DOB) below it in the same format.
3. Subtract day from day, month from month, and year from year.
4. If the day figure is negative, borrow 30 days (some use the actual days in that month) from the months.
5. If the month figure is negative, borrow 12 months from the years.
6. Give the result in years, months and days. For children under 2 years, express it in months (or weeks for neonates).

Worked example

• Day: 10 − 25 = −15, so borrow 1 month (30 days), giving 40 − 25 = 15 days, and the month becomes 5 − 1 = 4.
• Month: 4 − 1 = 3.
• Year: 2026 − 2024 = 2.
• Result: 2 years 3 months 15 days.

Premature babies: use corrected age

• Use corrected age to judge development until chronological age 2 years. - Textbook of Family Medicine 9e, Guidelines for Clinical Assessment
• The Harriet Lane Handbook says to use corrected age on growth charts up to 3 years.
• Use chronological age for the DQ in children born at term, and corrected age in preterm infants within these limits.

DQ calculation

• Language DQ = 12/24 × 100 = 50%.
• Motor DQ = 14/24 × 100 = 58%.
• Both domains are below 70%, so this meets the definition of GDD.