Introduction

Acromesomelic dysplasia (AMD), also known as short-limb dwarfism, is a rare inherited skeletal disorder that causes a short stature. It is characterised by acromelia, having short hand and foot bones and mesomelia, having short bones in the forearms and lower legs.. As a result, people with AMD have a short stature due to shortened forearms, lower legs, hands, feet, fingers and toes.¹ 

Clinical features

Characteristic physical signs^1,2

Some of the signs and symptoms include:

• Short forearms and lower leg bones
• Abnormal cartilage development
• Short and broad hands and feet
• Enlarged head
• Prominent forehead
• Pronounced back of the head
• Pug nose
• Flattened midface
• Fused joints of the arms and leg bones
• Abnormalities in the vertebrae
• Curve of the spine
• Delayed puberty - in some cases 

Diagnostic criteria

Clinical examination^1,2

During the examination with a specialist, the doctor will ask about the patient’s medical history and look for characteristics associated with AMD. These may include short and broad hands and feet at birth, as well as progressive skeletal abnormalities. They will also assess for short stature, shortening of the bones in the arms and legs, and limited range of movement. These symptoms typically are not apparent until early childhood.

Radiological assessment

CT and MRI scans can help doctors confirm the abnormal development and the premature joining of certain bones in the arms and legs. They may also detect an unusual fusion of the bones in the toes, fingers, hands and feet. 

Genetic testing

To better understand the genetics behind the disorder, your doctor may recommend genetic testing, including:

• Targeted gene sequencing - used to analyse specific mutation, such as those in the NPR2 and GDF5 genes
• Whole exome sequencing (WES) - a large-scale genetic test that looks at protein-encoding regions in all the genes. This is only used when other genetic testing does not seem to work

Differential diagnosis

Comparison with other skeletal dysplasias^1,3,4

There are a lot of disorders that can cause short limb dwarfism, including:

• Achondroplasia - individuals have very short arms and legs, while the torso remains a normal size. It is caused by a mutation in the gene called FGFR3, leading to the slow growth of the plates of the long bones, resulting in shorter bones
• Hypochondroplasia - similar to achondroplasia, where individuals will also have a shorter stature and shorter limbs. It is also caused by a mutation in the FGFR3 gene
• Langer mesomelic dysplasia - individuals will have a shorter stature, with extreme shortening of the long bones in the arms and the legs
• Acrodysostosis - a rare disorder that causes very short and malformed bones of the arms and the legs, as well as progressive growth retardation and malformation of the facial features
• Acromicric dysplasia - a very rare inherited disorder that causes short hands and feet because of delayed bone maturation

Management and prognosis^1,2

Therapeutic approaches

There are different treatment methods that your healthcare team may take, including

• Growth hormone therapy
• Orthopaedic interventions
• Physical therapy
• Corrective surgery

Long-term prognosis

The earlier the intervention, the better the management of AMD and the more effective the treatment becomes for your child, ultimately improving their quality of life.

Summary

AMD is a very rare and progressive disorder that affects the bones of the arms and legs, resulting in a type of short-limbed dwarfism characterised by acromegalia and mesomelia. Diagnosing AMD can be challenging, as many other disorders - such as achondroplasia and acrodysostosis - also cause short stature.