Tall Stature in Children
Tall stature is defined as a height above the 98th centile. While often considered socially acceptable, a sudden acceleration in growth or a height significantly above the mid-parental height can be a sign of an underlying medical condition. A comprehensive assessment is essential to differentiate between benign and pathological causes.
Causes of Tall Stature
The causes of tall stature are diverse and can be classified into normal variants and underlying medical conditions.
Normal Variants:
Familial Tall Stature: This is the most common cause. The child’s height is consistently high, but their height velocity is normal, and their final height is consistent with their parents’ stature.
Constitutional Tall Stature: These children have a rapid growth spurt in the preschool years but then return to a normal growth velocity. Their final adult height is within the normal range.
Endocrine Disorders:
Growth Hormone (GH) Excess: A rare cause of tall stature, usually due to a pituitary adenoma. This leads to gigantism in children before the growth plates fuse.
Precocious Puberty: Early onset of puberty leads to an initial growth spurt that can result in tall stature in childhood, but the early fusion of the growth plates often leads to a shorter final adult height.
Androgen or Oestrogen Excess: As seen in conditions like Congenital Adrenal Hyperplasia (CAH).
Hyperthyroidism: Excessive thyroid hormone can lead to an increase in height velocity.
Genetic Syndromes:
Marfan Syndrome: An autosomal dominant connective tissue disorder. Children with Marfan syndrome are typically tall and thin, with long limbs, fingers, and toes. They have a risk of aortic root dilation and lens dislocation.
Klinefelter Syndrome (47, XXY): Boys with Klinefelter syndrome are often tall and have disproportionately long limbs. They may also have small testes and learning difficulties.
Sotos Syndrome: Characterised by tall stature, macrocephaly, and learning difficulties.
Beckwith-Wiedemann Syndrome (BWS): Infants are large at birth and have a risk of hypoglycaemia and abdominal wall defects.
Clinical Assessment
History: A detailed history is essential, including birth weight, length, and a review of previous growth measurements. Ask about the timing of puberty and any symptoms of an underlying hormonal disorder.
Examination:
Accurate Measurements: Plot height, weight, arm span, and head circumference on a growth chart.
Proportions: Assess for disproportionate body segments. An arm span that is significantly greater than the height can be a sign of a connective tissue disorder like Marfan syndrome.
Pubertal Staging: Use Tanner staging to assess for precocious puberty.
Dysmorphic Features: Look for any syndromic features like a goitre, enlarged hands, or abnormal facial features.
Mid-Parental Height (MPH): Calculate the MPH to determine if the child’s tall stature is within their genetic potential.
Investigations
Investigations are not required for familial or constitutional tall stature. They are reserved for cases with an underlying suspicion of a pathological cause.
Bone Age: An X-ray of the left wrist is a key investigation to determine the bone age.
Hormonal Tests: If an endocrine cause is suspected, blood tests for TSH, T4, IGF-1, sex hormones, and a GH suppression test may be performed.
Genetic Testing: A karyotype is essential if a chromosomal abnormality like Klinefelter syndrome is suspected.
Imaging: An MRI of the brain may be considered to look for a pituitary adenoma.
Management
Reassurance and Monitoring: For familial and constitutional tall stature, the primary management is reassurance and monitoring of growth.
Treating the Underlying Cause: For pathological causes, management is directed at the underlying condition (e.g., surgery for a pituitary tumour, or GnRH analogues for precocious puberty).