Dwarfism - Causes of restricted growth

Restricted growth (dwarfism) may be caused by many different medical conditions, and is more noticeable in some conditions than others.

Causes of proportionate short stature

The main cause of proportionate short stature (PSS) is being born to small parents.

A less common cause is the body not producing enough growth hormone. The growth hormone deficiency may be present at birth, due to problems with the pituitary gland (a pea-sized gland below the brain responsible for producing several important hormones) or as part of another condition. Or it may start in childhood, as the result of an injury or disease affecting the head.

In about half of children with growth hormone deficiency, the cause is unknown. Growth hormone deficiency is estimated to occur in one in 3,500-4,000 children.

Other possible causes

Other possible causes of PSS include:

• chronic illnesses, such as those affecting the lungs, heart or kidneys
• steroid treatment for a chronic illness, such as arthritis
• genetic abnormalities such as Down's syndrome, Noonan syndrome, Turner syndrome and Prader-Willi syndrome
• malnutrition or poor absorption of food (for example, in coeliac disease) 

Disproportionate short stature

Conditions associated with disproportionate short stature (DSS) are usually caused by a faulty gene. Many children born with DSS have parents of average height and the change to the gene happens by chance. The affected genes stop the bones and cartilage developing properly, leading to restricted growth.

People with conditions that cause DSS may pass their condition on to their children. Conditions that cause DSS are usually present from birth.

The most common cause of DSS is a condition called achondroplasia. This causes shortened limbs (especially the upper arms and thighs), a large skull with prominent forehead, short hands and feet, and spinal abnormalities.

Other conditions that cause DSS include:

• hypochondroplasia
• mucopolysaccharide disease
• diastrophic dysplasia 
• spondyloepiphyseal dysplasia
• multiple epiphyseal dysplasia
• pseudoachondroplasia
• Conradi syndrome
• Ellis-van Creveld syndrome
• You can read more information on any of these rare conditions on the Restricted Growth Association website.