Introduction:
Larsen syndrome is a rare genetic condition. It affects the development of multiple bones in the body. Loren J. Larsen described the syndrome in a journal article in 1950, and it was later named after him. The Larsen syndrome affects about one in 100,000 babies each year and can cause a wide range of symptoms, even in children from the same family. Clubfeet, hypermobility, scoliosis, breathing difficulties, and short stature are the other symptoms associated with Larsen syndrome.
What Is Larsen Syndrome?
Larsen syndrome is a rare bone development disorder that affects the entire body. Larsen syndrome affects approximately one in every 100,000 newborns. FLNB gene mutations cause it. Symptoms associated with Larsen syndrome may differ greatly. Hip, knee, and elbow dislocations are common in affected people at birth. Clubfeet, feet that curve inward and upward, are another typical foot anomaly. In X-ray, affected people typically have tiny additional bones in their wrists and ankles. Their fingers often have blunt, square-shaped tips, especially the thumbs (spatulate).
What Causes Larsen Syndrome?
A genetic mutation causes Larsen syndrome. The FLNB (filamin B) gene mutation, crucial for good bone development during prenatal stages, triggers this condition. This might happen independently or be passed down from parents to their offspring. The FLNB gene codes for producing a protein known as filamin B. This protein plays a role in organizing the protein filaments network called the cytoskeleton, which provides cellular structure and facilitates cellular shape changes and movement. Filamin B binds to another protein called actin, assisting actin in forming the cytoskeleton's branching network of filaments. It also connects actin to many other proteins, allowing them to perform various functions within the cell, such as cell signaling, that controls how the cytoskeleton will alter as tissues mature and take on their final form.
How Is Larsen Syndrome Inherited?
One mutated gene copy in each cell is sufficient to develop Larsen syndrome as it is inherited in an autosomal dominant manner. Affected individuals occasionally inherit the mutation from just one affected parent. Certain instances of Larsen syndrome result from spontaneous gene mutations and can occur in individuals with no previous family history of the condition.
What Are the Symptoms Associated With Larsen Syndrome?
Larsen syndrome symptoms can vary significantly from person to person. Joint or skeletal abnormalities characterize typical symptoms associated with Larsen syndrome. The common symptoms are the following:
- Brachydactyly (fingers and toes that have become significantly shorter than normal).
- Short stature.
- Short toes and fingers.
- Club feet.
- Flat face.
- Broad thumb.
- Short nail.
- Cleft palate.
- Scoliosis (spine with abnormal lateral curvature).
- Defect in vertebral segmentation.
- Respiratory insufficiency.
- Finger syndactyly.
- Craniosynostosis.
- Abnormal cervical spine.
- Cardiovascular abnormalities.
- Hypertelorism (an excessively enlarged interpupillary gap, resulting in an increase in the gap between the orbits).
- Hyperflexibility of the joints.
- Dislocations of large joints.
- Prominent forehead.
- Accessory carpal bones.
- Dislocated elbows, hips, and knees.
- Hearing loss.
- Craniofacial anomalies.
- Bifid tongue.
- Malocclusion.
- Cataracts.
- Microdontia.
In addition, to these symptoms, people with Larsen syndrome may experience developmental delays and cognitive impairment. Nonetheless, the intensity of these symptoms may significantly differ among individuals.
How Is Larsen Syndrome Diagnosed?
Larsen syndrome is diagnosed based on family history and classic radiographic and clinical presentations. Given the diverse array of genetic mutations, there is currently no diagnostic test commercially accessible for detecting Larsen syndrome. Ultrasound is one of the most effective ways of diagnosing Larsen syndrome during pregnancy. Prenatal diagnosis is critical because it can assist families in preparing for the arrival of a baby with specific needs.
Prenatal ultrasound imaging can detect multiple joint dislocations, abnormal leg and knee positioning, a prominent forehead, a depressed nasal bridge, and club feet. As these symptoms are all linked to Larsen syndrome, they can be used to confirm that a fetus has the condition. The FLNB gene mutation can also be established using genetic testing. Imaging tests, such as X-rays and MRI (magnetic resonance imaging) scans, can also determine the severity of the joint and bone abnormalities associated with Larsen syndrome.
What Are the Treatments Available for Larsen Syndrome?
Treatment for Larsen syndrome varies since the disorder impacts multiple bodily functions. Sometimes patient observation is all that's needed. Surgery can be necessary in some situations to treat specific symptoms associated with Larsen syndrome. Depending on the patient's symptoms, many treatments are available for Larsen syndrome.
- Infants with Larsen syndrome are treated with joint manipulation as well as appropriate corrective casts.
- Severe joint abnormalities linked to Larsen syndrome can be addressed with orthopedic surgery.
- Physical therapy to improve strength and mobility.
- Nasal growth deficiency and cleft palate associated with Larsen syndrome require reconstructive surgery, and these individuals may also need speech therapy.
- The deformities of the face can be treated through reconstructive surgery.
- Cervical kyphosis associated with Larsen syndrome is dangerous because it causes the vertebrae to interrupt the spinal cord. Posterior cervical arthrodesis can be performed successfully on patients with cervical kyphosis.
- Genetic counseling is also advised for Larsen syndrome patients and their families.
What Is the Prognosis of Larsen Syndrome?
Children with Larsen syndrome can have normal lives and survive until adulthood with appropriate medical attention. Larsen syndrome patients usually suffer from painful or dislocated joints. Early in adulthood, these people may require hip or knee replacements. While Larsen syndrome can be fatal if left untreated, the prognosis is often favorable if patients have orthopedic surgery, physical therapy, and other treatments for the illness's symptoms.
Conclusion:
Larsen syndrome is an abnormality in bone development. The possible signs and symptoms are clubfoot, frequent hip, knee, and elbow joint dislocations before birth, flexible joints, and a characteristic appearance of the hands, face, feet, and fingers, with square-shaped fingertips. Genetic abnormalities in the FLNB gene cause Larsen syndrome, inherited autosomally dominantly.
The wrists and ankles of affected patients typically have little additional bones visible on X-rays. Other characteristics might include small stature, cleft palate, hypermobility, hearing loss, and an irregular spine curve that could cause issues, including weakness in the arms or legs. Individuals diagnosed with Larsen syndrome can lead a normal life with timely diagnosis and appropriate treatment.
