What Is Acromesomelic Dysplasia

Overview

Acromesomelic dysplasia is a rare skeletal disorder which is inherited as an autosomal recessive trait. Autosomal recessive is a pattern of inheritance characteristic of some genetic disorders. If a parent has an autosomal recessive trait, they will show no symptoms, but in order to pass it on to the children, both parents should carry the altered gene.

Acromesomelic dysplasia (AMD) is a condition of inhibition of the growth of certain long bones that results in short stature called short limb dwarfism. They commonly affect the bones in the forearms, lower legs (shortening of bones in this area is known as mesomelia) and bones in the hands and feet (shortening of bones in this area is known as acromelia).

At birth the hands and feet of the child may appear abnormally short and broad, overtime during the first year of life the short hands, fingers, feet and toes become more obvious.¹

Types of acromesomelic dysplasia

1. Acromesomelic dysplasia, Maroteaux type

Acromesomelic Dysplasia, Maroteaux type, is a rare form of skeletal dysplasia characterized by severe shortening of the limbs, particularly affecting the middle (mesomelic) and distal (acromelic) segments. This condition is distinct from mucopolysaccharidosis type VI (MPS VI), also known as Maroteaux-Lamy Syndrome, which is caused by a deficiency of the enzyme arylsulfatase B (ASB).

Key characteristics are:

• Skeletal Abnormalities: The primary feature is the significant shortening of the bones in the forearms and lower legs, leading to short stature. This condition may also involve abnormalities in the hands and feet, such as short and broad fingers and toes.
• Facial Features: Unlike MPS VI, the facial features in Acromesomelic Dysplasia, Maroteaux type, are not as prominently affected. However, some individuals may exhibit mild facial dysmorphisms.
• Genetic Cause: This condition is inherited in an autosomal recessive pattern, meaning that both parents must carry and pass on the mutated gene for the child to be affected.

The management of Acromesomelic Dysplasia, Maroteaux type, focuses on addressing the skeletal abnormalities and improving the quality of life for affected individuals. There is no cure for the condition, but treatment options may include:

• Orthopedic Interventions: Surgical procedures may be considered to correct deformities or improve limb function. Limb lengthening surgeries might be an option for some individuals.
• Physical Therapy: To enhance mobility and muscle strength, helping to maximize the individual's functional abilities.
• Supportive Care: Use of orthotic devices to support joints and improve posture, and pain management strategies.

Important Distinction: It is crucial to differentiate between Acromesomelic Dysplasia, Maroteaux type, and MPS VI (Maroteaux-Lamy Syndrome). While both conditions can affect skeletal development, MPS VI is a lysosomal storage disorder with systemic implications due to the accumulation of glycosaminoglycans, requiring different management strategies, including enzyme replacement therapy.

2. Acromesomelic dysplasia, Grebe type

Grebe dysplasia is a severe limb abnormality, including fused fingers and toes. It is caused by mutations in the fibroblast growth factor receptor 3 (FGFR3) gene. Symptoms are : 

• Severe shortening of long bones, and a characteristic feature is the fusion of the finger and toe bones.
• Facial features are not that prominently seen in this condition.

Treatment and management are mainly focused on function and mobility challenges of the bones. The application of limb-lengthening procedures can help with mobility and quality of life.³

3. Acromesomelic dysplasia, Hunter-Thompson type

It is caused by mutations in the gene fibroblast growth factor receptor (FGFR3). It causes deformity in the growth and development of the bone. Features are : 

• Severe limb shortening of both forearm and legs, including fingers and toes.
• The patient may also experience restricted joint movement due to the deformity.
• Facial features include a broad forehead and flat nose, but these are mild in comparison to the limb deformity. 
• Shortened fingers and toes.

The treatment mainly focuses on the functional and mobility challenges of the bones. Orthopaedic procedures like limb lengthening and surgeries are done to improve the mobility and functions of the limb.⁴

Signs and symptoms

1. Limb Shortening - Acromesomelic dysplasia is the inhibition of the growth of the long bones, that is, forearms and lower legs. They have short forearms and lower legs. They exhibit short stature. These findings are noticed during the first year of life.
2. Hand and Foot Deformities - Abnormal development of cartilage can also affect the bones of the hand and feet. It causes shortened fingers and toes.
3. Spinal Deformities - Spinal deformities are not the primary characteristics of acromesomelic dysplasia, but they are the secondary complications resulting from the deformity of the limbs. Shortening of the lower limbs can affect the alignment of the pelvis and lower spine, it can result in the curvature of the spine and cause lumbar lordosis (inward curvature of the spine).
4. Joint Abnormalities - Acromesomelic dysplasia affects the bones, which causes abnormalities and affects the individual's mobility and functions. Abnormal shortening of the limbs causes tightening of ligaments and tendons around the joints, causing limited joint movement, including knee, elbow and fingers. Bowing of the legs and knock-knees are common abnormalities seen, and knee deformity causes gait abnormality.
5. Facial Features - Infants have facial abnormalities such as prominent foreheads, flattened faces and flat noses. They have enlarged heads (macrocephaly) and prominence of the back portion of the head (occipital prominence).
6. In some individuals, there may be degeneration, stiffness, tenderness and pain in the elbow due to osteoarthritis. 

Diagnosis

• Physical Examination - Acromesomelic dysplasia is diagnosed in the first year of life during clinical evaluation, where the detailed patient history, family history, and characteristic findings help in understanding the abnormality.
• X-ray - Imaging techniques help in understanding the abnormality and the premature fusion of the bones. The shortening of the long bones and fusion of fingers and toes.²
• Genetic Testing - Genetic testing is used to confirm the diagnosis and to identify specific genetic mutations.^5,6

Differential diagnosis

As there are different types of genetic and skeletal disorders, healthcare providers may need to rule out the conditions which have similar symptoms. Differential diagnosis may include conditions like achondroplasia, hypochondroplasia, and other skeletal dysplasias.

Management and treatment

Orthopaedic surgeons are the doctors who perform the surgery and do the treatment related to bone. Without proper treatment, the acromesomelic condition can worsen and affect the quality of life.

1. Surgical procedure

Acromesomelic dysplasia causes shortening of the limbs, and this causes deformity in the spine, knees, and elbow and can result in restricted mobility and a deformed appearance. Surgical procedures like limb lengthening can be performed to improve mobility and stature. Surgical procedures for joint deformities can help to correct the deformity and improve mobility.

2. Physical therapy and rehabilitation

Physical therapists work with individuals having acromesomelic dysplasia and provide them with personalised exercise according to their deformity. This helps increase mobility and muscle strength and improves quality of life.

3. Orthotic devices

Orthotic devices such as braces and splints help in supporting the joints, improve posture and improve mobility.

4. Medication

People with acromesomelic dysplasia may experience pain and discomfort due to the joint deformity, and medicines are advised to relieve the symptoms.

5. Genetic counselling

This is an important part in the cases where genetic mutation is diagnosed. Genetic counsellors give information regarding the inheritance of genetic mutation, the likelihood of passing it to the next generation and also about family planning to prevent it.

6. Psychological support

Living with acromesomelic dysplasia can be challenging both physically and mentally for the individual and the family members. Counselling helps individuals and their family members to accept and move on with their health condition.

FAQs

What is the life expectancy with acromesomelic dysplasia

A person diagnosed with acromesomelic dysplasia has a normal life expectancy as others. Acromesomelic dysplasia is a condition of shortening of long bones. It is also known as short-limbed dwarfism.

How do you treat acromesomelic dysplasia?

Acromesomelic dysplasia is treated with the help of orthopaedic surgery to rectify the deformity and increase mobility. Physical therapy and the usage of orthotic devices help to improve the abnormality and improve the quality of life.

What are the causes of acromesomelic dysplasia?

Acromesomelic dysplasia is a skeletal disorder which is inherited as an autosomal recessive trait. If a parent has an autosomal recessive trait, they will show no symptoms, but in order to pass it on to the children, both parents should carry the altered gene.

How rare is acromesomelic dysplasia

Acromesomelic dysplasia is a rare skeletal disorder which is inherited as an autosomal recessive trait. Autosomal recessive means when there are two copies of an abnormal gene present in the person.

Summary

Acromesomelic dysplasia (AMD) is a condition of inhibition of the growth of certain long bones that results in short stature called short limb dwarfism. They commonly affect the bones in the forearms, lower legs (shortening of bones in this area is known as mesomelia) and bones in the hands and feet (shortening of bones in this area is known as acromelia). It is a rare skeletal disorder which is inherited as an autosomal recessive trait. Acromesomelic dysplasia is diagnosed in the first year of life during clinical evaluation and confirmed through imaging techniques. It is incurable, but surgical procedures like limb lengthening can be used to improve mobility and stature. Surgical procedures for joint deformities can help to correct the deformity and improve mobility.