Carpenter Syndrome - Causes, Symptoms, Diagnosis, and Treatment

What Is Carpenter Syndrome?

Carpenter syndrome is a type of rare genetic group of conditions known as "acrocephalopolysyndactyly" disorders. All kinds of acrocephalopolysyndactyly are characterized by the following:

• Craniosynostosis: Premature closure of the fibrous joints between some of the bones of the skull.

• Acrocephaly: The pointy appearance of the head due to premature closure of the sutures.

• Syndactyly: Fusions of digits (fingers and toes).

• Polydactyly: The presence of more than the average number of digits.

Carpenter syndrome is also called acrocephalopolysyndactyly disorder (ACPS) type 2. Therefore, to summarize, Carpenter syndrome can be defined as a condition marked by deformities of the fingers and toes, developmental issues, characteristic facial abnormalities, and the early fusion of certain skull bones. Therefore, carpenter syndrome is classified as; Carpenter syndrome type 1 and Carpenter syndrome type 2. In 1901 two sisters and one brother were diagnosed with Carpenter syndrome for the first time. Carpenter syndrome, however, was not identified as a separate disease entity until 1966.

What Causes Carpenter Syndrome?

Carpenter syndrome is a genetic disorder that occurs due to mutation or variations in a particular gene. A RAB23 gene mutation typically causes Carpenter syndrome. The RAB23 gene codes for a protein that is necessary for vesicle trafficking, a process that transports proteins and other molecules inside cells in sac-like structures known as vesicles.

However, the condition may also develop in a small group of people due to MEGF8 gene mutation. The MEGF8 gene is responsible for providing instruction for the formation of specific proteins whose functions are still unknown. According to the structure of the gene, it is speculated that it may be responsible for helping proteins connect with one another and for cell adhesion. The same mutations may affect members of the same family, yet they may have various symptoms of varying severity (intrafamilial variability).

Carpenter syndrome is inherited (genetically passed from parents to their children) in an autosomal recessive manner, which means a person receives two copies of an atypical gene for the same trait, one from each parent. People with MEGF8 gene mutations are more likely than those with RAB23 gene mutations to have dextrocardia (presence of heart on the right side of the chest), various abnormalities of organ placement, and less severe craniosynostosis. However, the cause of this difference is also unknown.

What Are the Symptoms of Carpenter Syndrome?

The symptoms of Carpenter syndrome include:

• Acricephaly: Carpenter syndrome frequently manifests at birth or very soon after. The top of the skull may appear abnormally conical due to craniosynostosis.

• Brachycephaly: The head may appear short and broad.

• Craniofacial Asymmetry: The skull and face usually appear different from one side to the other because the cranial sutures frequently fuse unevenly.

• Eyefold appears down, slanting.

• Flat nasal bridge.

• Low-set ears.

• Small and underdeveloped upper and lower jaws.

• Abnormally short fingers and toes.

• Soft tissue partial fusion between certain digits. Soft tissue fusion in digits is most common between the third and fourth fingers.

• The presence of extra digits (fingers or toes) is also known as supernumerary digits.

• Short height or stature.

• Congenital heart defects with respect to the position and structure of the heart.

• Obesity (mild to moderate).

• Abdominal wall weakness could allow the intestine to protrude near the navel.

• Testes fail to descend to the scrotum.

• Intellectual disabilities (mild to moderate). Some people with this illness do, nevertheless, have average intellect. Since the severity of craniosynostosis does not seem to be associated with the severity of intellectual disability, the cause of intellectual disability remains unknown.

• Knees angled inward, a rounded upper back like kyphoscoliosis or hunchback, and other skeletal abnormalities, including malformed hips, are also frequently seen.

• Occasionally, individuals with Carpenter syndrome will have tissues or organs in their chest and abdomen that are present in the mirror-image position. This unusual positioning could impact multiple internal organs.

How Common Is Carpenter Syndrome?

Carpenter syndrome is a rare disorder; the scientific literature lists information on only about 70 cases. Men and women tend to be affected by Carpenter syndrome about equally. The same abnormal mutation was discovered in ten patients whose sequence analyses for the disease-causing gene were performed. The high incidence of a genetic condition in a small or inbred community is a result of the fact that many individuals of the population are descended from a common ancestor who had the disease-causing mutation, which is indicative of a founder effect in patients of northern European heritage.

How Is Carpenter Syndrome Diagnosed?

Carpenter syndrome is diagnosed in the following ways:

• Based on a clinical examination and characteristic symptoms, a healthcare professional may suspect Carpenter syndrome. However, it has symptoms and signs similar to that of Greig cephalopolysyndactyly syndrome, another genetic disorder. These two conditions can be misdiagnosed due to their overlapping characteristics, which include craniosynostosis, polydactyly, and cardiac abnormalities; further investigations and genetic testing are frequently necessary for a precise diagnosis.

• Imaging tests like a CT (computed tomography) scan and MRI (magnetic resonance imaging) may be done to see the structural abnormalities present in the skull, heart, skeleton, and other organs.

• Heart functioning may be evaluated with the help of an electrocardiogram (EKG) or echocardiogram (ECG).

• Hearing tests may also be done.

• Preimplantation genetic testing or prenatal testing before birth may be advised if a family has a Carpenter syndrome mutation history. This may involve amniocentesis, which evaluates amniotic fluid, or chorionic villus sampling, which examines a portion of the placenta. This test is frequently performed along with prenatal ultrasonography. An ultrasound can show an unusually shaped head, extra toes or fingers, heart problems, organs placed incorrectly, etc.

How Is Carpenter Syndrome Treated?

Carpenter syndrome is treated according to the distinct symptoms that are present in each patient. Such care might necessitate the coordinated efforts of a group of medical experts.

• Early surgery may be suggested to help prevent or treat premature closure of cranial sutures because craniosynostosis can occasionally result in abnormally elevated pressure on the brain and inside the skull (intracranial pressure). In addition, according to certain reports, early surgical intervention may, in some cases, aid in preventing intellectual disability.

• To help rectify further craniofacial malformations, polydactyly, syndactyly, and other skeletal defects related to the disease, corrective and reconstructive surgery may, in some cases, also be advised.

• Congenital heart problems may also require therapy with specific drugs, surgical treatment, and/or other treatments. The extent and site of the anatomical abnormalities, their related symptoms, and other considerations will influence the surgical procedures that are carried out.

• A hearing aid is advised for people with hearing impairment, and speech therapy may be recommended for individuals with speech impairment.

• Early intervention may be crucial for children with Carpenter syndrome to attain their full potential. Specific physical therapy and other medical, social, or vocational assistance are a few of the special services that may be advantageous to the affected children.

Conclusion

Carpenter syndrome is a very rare genetic disorder characterized by hallmark symptoms like acrocephaly, syndactyly, polydactyly, facial deformities, etc. The condition can be inherited in an autosomal recessive fashion and manifest soon after birth. Although Carpenter syndrome is a genetic condition and cannot be prevented, a couple can undergo preimplantation genetic testing to reduce the risk of having a child with carpenter syndrome. Some affected kids go on to lead independent lives as adults. However, some people with intellectual and physical impairments require long-term medical and social support. In addition, the life expectancy of a child with Carpenter syndrome is often short due to the associated heart defects.