Metatrophic Dysplasia: Causes, Symptoms, Diagnosis, and Management

Introduction

Metatrohic dysplasia (MTD) is a skeletal disorder. It is a disease of the long bones (the metaphysis). It becomes knobby, and the spine has a flattening of the vertebral bodies. The characteristic feature of MTD is short limbs with limitation and enlargement of joints. They have short limbs and other skeletal deformities. These deformities can change with time.

What Is Metatrophic Dysplasia?

The term meta trophic comes from the Greek word, which means “changing forms,“ patients of metatrophic dysplasia have an abnormality in their growth plates. Due to this, the vast portion of the long bones (the metaphysis) is knobby in appearance, and the spine has a flattening of the vertebral bodies. People suffering from this disease appear to have a short limb early in life and later seem to have a short trunk. Affected infants are born with a narrow chest, unusually short arms and legs, and dumble-shaped long bones.

Beginning in early childhood, people with this disease develop abnormal side-to-side and front-to-back spine curvature (scoliosis and kyphosis are often called kyphoscoliosis when they occur together.). The curvature gets worse with time and is resistant to treatment. Due to this severe kyphoscoliosis, the patient has a very short torso about the length of their arms and legs.

Few individuals born with MTD have an elongated tailbone, often called a coccygeal tail. It is made up of rigid but flexible tissue cartilage. The coccygeal tail often shrinks with time. It is a rare condition that is a genetically transmitted autosomal-dominant disorder, which means that a dominant gene from one parent is enough to cause the disease.

What Are the Causes of Metatrophic Dysplasia?

Metatrophic dysplasia is caused due to mutations in the TRPV4 gene, which provides instructions for making a protein as a calcium channel. The TRPV4 gene is responsible for transporting the positively charged calcium atoms (calcium ions) across the cell membrane into the cells. This channel is found in many types of cells. It is suggested that it plays an essential role in the normal development of bone and cartilage.

What Are the Signs and Symptoms Associated With Metatrophic Dysplasia?

The signs and symptoms associated with metatrophic dysplasia can vary from mild to severe conditions that can be life-threatening. Symptoms can be noticed during fetal growth and as a newborn. Some common symptoms include-

• Coccyx (tailbone) is the long bone below the buttocks.

• A high forehead is seen in the affected individuals.

• Limbs appear short and flexed.

• Unstable neck.

• Cataract.

A few patients may also have hydrocephalus or restrictive lung disease. The orthopedic conditions seen in patients with meta-trophic dysplasia are-

• Cervical instability.

• Kyphosis- sharp angular back rounding can lead to spinal stenosis(spinal cord narrowing).

• Scoliosis (curvature of the spine appears) occurs early and is progressive.

• Abnormal cortical bone(compact bone) morphology.

• Abnormal enchondral ossification is a type of replacement ossification in which the bone tissue replaces the cartilage.

• Abnormal morphology of vertebral bodies.

• Any structural abnormality of the intervertebral disc.

• Joint stiffness.

• Halbered-shaped pelvis.

• Long thorax.

• Cleft palate.

How Is Metatrophic Dysplasia Diagnosed?

It can be diagnosed in the prenatal stage. A prenatal sonogram shows signs including a narrow chest and a dumb-bell appearance in the long bones. Mostly, doctors diagnose meta trophic dysplasia with a complete medical history, physical examination, and diagnostic tests.

Other diagnostic procedures may include-

• X-rays of the cervical spine to monitor neck stability and of the thoracic and lumbar spine to evaluate for kyphosis and scoliosis. The radiographical features of this disease indicate small, flat, diamond-shaped vertebral bodies in the early infancy period. Platyspondyly (flattening of vertebral bodies) and vertical bone anterior wedging are also seen.

• Pedicles seem to be over-faced. The lateral border of the vertebral body may appear outside the lateral edge of the pedicle. The thorax appears narrow in infancy and early childhood, and the ribs appear short.

• The long bones appear shortened with metaphyseal flare and epiphyseal dysplasia, giving them a dumble-shaped appearance.

• MRI (magnetic resonance imaging) of the cervical, thoracic, and lumbar spine may be taken to monitor cervical instability and spinal stenosis.

• Genetic testingof the TRPV4 gene is also suggested so that it can give a confirmatory diagnosis.

How Is Meta-Trophic Dysplasia Treated?

The treatment should avoid skeletal deformity and remove the obstruction in the normal functioning of the pulmonary system. The treatment of meta trophic dysplasia depends on the underlying orthopedic condition. Some of the possible treatments are discussed below-

• Braces can be placed till the time skeletal maturity is achieved.

• Treatment for Cervical Instability- A spinal fusion is a surgical procedure that can be performed at the right time and in the appropriate patient; it can stop the disease and helps in the improvement of the patient. Decompression can be done if there is the presence of stenosis.

• Treatment for Scoliosis- Fusion of the spine can be done.

• Treatment for Thoracolumbar Kyphoscoliosis- Corrective spine surgery is suggested.

• Surgery of short stature can also be done, but that is decided based on different cases, for example, as per the severity of disease in other individuals that can be progressive.

Conclusion

This article gives details of meta trophic dysplasia, its causes, signs and symptoms, and possible treatment. Metatrophic dysplasia is a skeletal disorder due to a genetic mutation in the TVR4 gene. This is caused due to autosomal resistance. It is a rare disorder but can be severe. The person affected with this disease appears short-statured, with short extremities, a broad forehead, and a long trunk. The chest becomes elongated, and the bones are dumbbell-shaped. People suffering from meta-trophic dysplasia can develop arthritis at an early age. Other mild to severe life-threatening symptoms can be seen in this disease. This disorder starts during fetal growth, in early infancy, or after some time. Fetal sonograms can diagnose it during pregnancy, and X-rays and MRIs can be done after birth. The selection of appropriate treatment at the correct time is an important task. The treatment can be surgical, such as spine corrective surgery, a fusion of the spine, and neurosurgical.