Seckel syndrome

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at August 26, 2016
StartDiseasesSeckel syndrome

Seckel syndrome, also called bird-headed dwarfism, microcephalic primordial dwarfism, or Harper’s syndrome is an extremely rare inherited disorder. It is characterized by dwarfism, deformities of the head and facial area, and moderate to severe intellectual disability. Life expectancy for those with the disorder is around 50 years of age.

Contents

Definition & Facts

Seckel syndrome causes delays in the growth of a fetus prior to birth, called intrauterine growth restriction. Infants have an unusually low birth weight and stunted growth occurs as the child develops. The condition is considered to be a form of primordial dwarfism.

Although the body is small in stature, the limbs are typically proportionate to the rest of the body. This separates Seckel syndrome from other forms of dwarfism where the arms and legs are disproportionately short.

The disorder is named after Dr. Helmut G. Seckel who produced the first definitive publication in 1960 describing the condition based on two children that he personally treated and 13 other cases that had been documented in past literature. The exact number of incidents is unknown, but over 100 cases have been reported in medical journals since 1960.

Symptoms & Complaints

Infant birth weight is usually around 1,540 grams (3.3 pounds). Those with the disorder typically have an abnormally small head, known as microcephaly. A condition called craniosynostosis, where the fibrous joints in the skull close prematurely, may cause the head to appear abnormally long or short.

Inside the small head, the brain is underdeveloped and about half of children with Seckel syndrome have an IQ of less than 50. Developmental delays are commonly seen in children, while intellectual disability may not be noticeable until they are older. Children with the condition are often described as having a nice disposition but may be hyperactive and easily distracted.

Seckel syndrome is easily recognized due to the unusual facial features that are commonly present. Most obvious is the presence of a protrusion of the nose that creates a “beak-like” appearance. Those with the condition may also have a narrow face, unusually large eyes with downward-slanting eyelids, low-set ears without lobes, and an abnormally small jaw.

The eyes may be crossed or there may be a cleft lip and cleft palate. Facial asymmetry and other skeletal abnormalities may also exist. Dental problems may be present including crowded or improperly placed teeth and an underdevelopment of tooth enamel.

Disorders or abnormalities with the sex organs may exist. Testes may fail to descend in males (cryptorchidism), and females may exhibit an abnormally enlarged clitoris. Children may have excessive body hair (hirsutism) or a deep crease across the palm of the hands (simian crease).

The pinky finger may be permanently bent, and the radial bone in the forearm may be dislocated. Elbows may dislocate, hip dysplasia is common, and children may be unable to fully extend their knees.

Curvature of the spine (kyphoscoliosis), club foot, and a missing rib are also possible symptoms. Blood disorders such as bone marrow deficiency or anemia are present in about 25% or less of cases.

Causes

Seckel syndrome is caused by mutations of the genes on chromosome 3 and chromosome 18, chromosome 14. Seckel syndrome is divided into eight different subcategories depending on the specific gene mutation. The condition is inherited as an autosomal recessive trait, meaning that each parent must pass the same abnormal gene on to the child.

If a child receives the gene from only one parent, he or she will be a genetic carrier but will not show any symptoms. When two carrier parents conceive a child, each pregnancy has a 25% chance of resulting in an affected child and a 50% chance of having a child who is a carrier. There is a 25% chance that the child will receive two normal genes and be genetically free of the disorder. Risk of inheriting the condition is equal for both males and females, and it is found in less than one in 10,000 live births.

Diagnosis & Tests

Diagnosing rare genetic disorders presents a challenge for physicians. Technological advances in ultrasonography have allowed some cases of Seckel syndrome to be diagnosed before birth. Once a child is born, the initial diagnosis is typically based on the presence of physical symptoms.

Clinical evaluation, a series of genetic testing and other specialized tests, and a detailed evaluation of family history will also help with diagnosis. X-rays are sometimes needed to distinguish the syndrome from other similar disorders. In some cases, diagnosis may not occur until a child is old enough for the symptoms of the condition, such as short stature and intellectual disability, to fully manifest.

Treatment & Therapy

There is no cure for Seckel syndrome. Treatment is based on managing the medical problems that accompany the disorder. The most commonly treated symptoms are blood disorders like leukemia and anemia that can be managed with medication and therapy.

Parents of children affected by Seckel syndrome will be well served to find a physician who specializes in genetic conditions. They may also wish to consult with neurologists, speech therapists, and education specialists.

Families of children with Seckel syndrome will need social support and counseling services to manage the many issues related to severe intellectual disability. School-age children may benefit from special education or early intervention programs. Some clinical trials are also available for individuals affected by the condition.

Prevention & Prophylaxis

Since it is a genetic disorder, there is no sure way to prevent Seckel syndrome. If a couple has a child with the condition, they may opt for genetic counseling prior to conceiving any additional children. This can help couples to evaluate the risk and offer guidance. They also often offer support groups to help families cope with the disorder.

Individuals with a family history of the disorder may also seek genetic counseling prior to conceiving in order to assess the risk of transmitting the gene to future generations.