The term global developmental delay refers to delay in all milestones (but particularly language, fine motor and social skills) and is particularly worrying as it generally indicates significant learning disability. Delay in a single area is much less concerning. Warning signs suggesting significant developmental problems are described in the table on p. 20, Chapter 3.

You may need to repeat assessments to get an accurate view of a child’s difficulties, and may need to refer on to an appropriate therapist for further assessment and guidance. When developmental difficulties are complex, the child should be seen by a Child Development Team (Chapter 42) for assessment and therapy. It is essential that parents’ concerns are properly addressed. Ongoing parental anxiety in itself can be damaging to the child.

Severe Learning Disabilities (Mental Retardation)

The commonest causes of severe learning disability are Down’s syndrome (Chapter 63), fragile X (Chapter 63) and cerebral palsy (Chapter 42). As the field of genetics advances, and genetic databases have been developed, more diagnoses are being made, particularly in children with congenital anomalies and dysmorphic features. It is therefore worth taking blood for genetic analysis. However, more than one third of children with global developmental delay still have no specific diagnosis.

Intrauterine Infections

Primary infection with rubella, cytomegalovirus (CMV) or toxoplasmosis during early pregnancy can cause severe fetal damage, leading to multiple handicaps and microcephaly. Visual and hearing deficits are common.

Fetal Alcohol Syndrome

The fetal alcohol syndrome is a common cause of learning disabilities. It is caused by a moderate to high intake of alcohol during pregnancy. Children have a characteristic facial appearance, cardiac defects, poor growth and microcephaly. The severity of the problems relate to the quantity of alcohol consumed.

Congenital Hypothyroidism

Lack of thyroid hormone in the first years of life has a devastating effect on both growth and development. However, since neonatal screening has been introduced, it is now a rare cause of developmental delay. The defect is due to abnormal development of the thyroid or inborn errors of thyroxine metabolism.

Babies usually look normal at birth, but may show features of severe hypothyroidism (once called cretinism), including coarse facial features, hypotonia, a large tongue, an umbilical hernia, constipation, prolonged jaundice and a hoarse cry. Older babies or children have delayed development, lethargy and short stature. Thyroid function tests reveal low T4 and high TSH levels.

Congenital hypothyroidism is one of the few treatable causes of learning disabilities. Thyroid replacement is needed lifelong and must be monitored carefully as the child grows. If therapy is started in the first few weeks of life and compliance is good, normal growth and development can be achieved.

Inborn Errors of Metabolism

This group of disorders are caused by single-gene mutations, inherited in an autosomal recessive manner, so consanguinity is common. They present in a variety of ways of which developmental delay is one, but neonatal seizures, hypoglycaemia, vomiting and coma may also occur. Children sometimes have coarse features, microcephaly, failure to thrive and hepatosplenomegaly. These inborn errors of metabolism are rare; phenylketonuria is the commonest and is routinely screened for in all neonates.

Neurodegenerative Disorders

A neurodegenerative disease is characterized by progressive deterioration of neurological function. The causes are heterogeneous and include biochemical defects, chronic viral infections and toxic substances, although many remain without an identified cause. Children may have coarse features, fits and intellectual deterioration, and microcephaly. The course is generally one of relentless and inevitable neurological deterioration, although bone marrow transplantation is now providing hope in some conditions

Neurocutaneous Syndromes

The neurocutaneous syndromes are a heterogeneous group of disorders characterized by neurological dysfunction and skin lesions. In some individuals there may be severe learning disabilities and in others intelligence is normal. Examples include Sturge–Weber syndrome, neurofibromatosis and tuberous sclerosis. The aetiology of these problems is not known, but most are familial.

Abuse and Neglect

Emotional abuse and neglect can have serious consequences for a child’s developmental progress. The delay is often associated with failure to thrive. On presentation the child may be apathetic, look physically neglected with dirty clothing, unkempt hair and nappy rash, and there may be signs of non-accidental injury. If there is any suggestion of regression of developmental skills, chronic subdural haematomas (which can occur as a result of shaking injuries) should be considered.

Intensive input and support is needed. Day nurseries can provide good stimulation, nutrition and care. If children continue to be at risk for ongoing abuse or neglect they must be removed from the home. The prognosis depends on the degree of the damage incurred and how early the intervention is provided. Children who require removal from the home often have irreversible learning and emotional difficulties.