Global and isolated developmental delay

Developmental delay is slower acquisition of expected functional skills compared with peers. Global developmental delay is used in children under 5 when at least two domains are significantly affected; intellectual disability is assessed later through both intellectual and adaptive functioning. A mild variation, developmental difference and clinically significant delay are separated by trajectory, function, standardised assessment and context rather than one milestone.

Map each domain separately. Gross motor includes posture and mobility; fine motor includes hand use and visual-motor integration; language includes receptive, expressive and pragmatic communication; cognition includes learning and problem-solving; social-emotional function includes reciprocity and regulation; adaptive skills include feeding, dressing, toileting and safety. Dissociation between domains can be diagnostically useful, while global delay suggests a more widespread process.

History starts before conception. Ask about parental health and learning, consanguinity and similarly affected relatives; pregnancy infection, medication, alcohol or drug exposure; fetal growth; gestation, delivery, encephalopathy, neonatal seizures and screening; feeding and growth; serious infection, trauma and seizures; chronic illness and medicines. Construct a three-generation family history and ask about pregnancy losses and adult neurological disease when a genomic cause is possible.

Describe developmental onset and course. Establish which skills are secure, emerging or absent, how the child communicates needs and whether function differs across settings. Correct for prematurity early in life. Ask about any loss, plateau, episodic decline, fatigue or worsening during illness. Obtain nursery or school information and review opportunities to hear, see, move, play and interact in every language used.

Examination includes accurate weight, length or height and head circumference plotted serially; dysmorphism and skin; vision and hearing behaviour; cardiac, abdominal and musculoskeletal examination; and a full neurological assessment of cranial nerves, tone, power, reflexes, movement, coordination, gait and symmetry. Note congenital anomalies, organomegaly, neurocutaneous marks and body proportions. Photographs for dysmorphology require appropriate consent and secure handling.

Isolated gross-motor delay can reflect normal variation, cerebral palsy, muscular dystrophy, congenital myopathy, spinal or orthopaedic disease, hypothyroidism or limited opportunity. NICE recommends child-development referral when sitting or walking thresholds are missed or hand function is asymmetric, and CK consideration in boys. Physiotherapy and occupational therapy should not wait for a complete diagnosis.

Isolated speech or language delay may reflect hearing loss, developmental language disorder, speech-sound disorder, autism, intellectual disability or a limited assessment in the child's weaker language. Formal audiology is essential because newborn screening does not exclude acquired or progressive loss. Receptive difficulty, loss of language, poor gesture or joint attention and broader adaptive problems increase concern beyond isolated expressive delay.

Global delay may arise from chromosomal or single-gene disorders, brain malformation, prenatal or perinatal injury, infection, cerebral palsy, neurometabolic disease, endocrine or nutritional disease and severe environmental adversity. Sometimes no cause is identified. Aetiology can clarify recurrence risk, surveillance and treatment, but investigation must not make support conditional on receiving a molecular diagnosis.

First-line tests are phenotype guided. Formal hearing and vision testing and a standardised developmental profile have high immediate value. Common blood tests may include FBC, ferritin, U&E, liver and bone profile, thyroid function, CK and coeliac serology when history or examination supports them. Test lead only with exposure risk and use ammonia, lactate, plasma amino acids, acylcarnitine or urine organic acids when regression, episodic illness, organomegaly, movement disorder or another metabolic clue is present.

In England, genomic testing should follow the current National Genomic Test Directory. Moderate-to-profound unexplained developmental delay or intellectual disability, congenital anomalies, dysmorphism and a suggestive family history can meet specific pathways; isolated autism or mild intellectual disability alone may not. Record detailed phenotype and Human Phenotype Ontology terms, obtain informed consent and involve clinical genetics or the Genomic Laboratory Hub as the pathway requires.

MRI brain is most useful with abnormal head size or trajectory, focal neurology, seizures, regression, cerebral palsy of unclear cause or suspected structural abnormality. It may require sedation or anaesthesia, so ask a specific question. EEG supports evaluation of suspected seizures or epileptic encephalopathy but cannot exclude epilepsy when normal. Sleep EEG can be crucial when regression or school deterioration suggests sleep-activated epileptiform activity.

Management starts with the child's current barriers. Physiotherapy addresses posture and mobility, occupational therapy hand and adaptive function, speech and language therapy communication and eating, and audiology or ophthalmology sensory access. Use augmentative and alternative communication early when speech is limited. Review nutrition, sleep, constipation, pain and behaviour because untreated discomfort can suppress participation.

Coordinate health, education and social care around one profile and named lead. Provide accessible information, genomic counselling when relevant, carer support and an emergency plan for epilepsy or metabolic risk. Review safeguarding without equating disability with neglect and involve the child through their preferred communication.