Phocomelia

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at August 19, 2016
StartDiseasesPhocomelia

Phocomelia or phocomelia syndrome is associated with a largely banned drug called thalidomide. While the drug is no longer available to women as a way to treat the symptoms of morning sickness, studies continue to determine how thalidomide caused such severe birth defects. It is often called simply PS for short.

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Definition & Facts

The word "phocomelia" literally translates to mean "seal limb." This name was chosen for the syndrome since its chief symptom is children born with arms that have been said to resemble seal flippers.

More than 10,000 children who were exposed to thalidomide in utero were born with deformed limbs before the drug's negative effects were discovered and it was withdrawn. An estimated 40 percent of these babies passed away before the age of 1. Half of affected babies spontaneously aborted before delivery.

Phocomelia continues to manifest even though thalidomide's dangers are well understood. There are other causes for these kinds of symptoms, and a related condition is Roberts syndrome which is also called pseudothalidomide as a reference to the most well-known trigger for the disease.

Symptoms & Complaints

The main symptom of phocomelia is shortened or absent arms or legs. Cases range from very mild to severe. Legs are less frequently affected than arms. The most severe cases are called tetraphocomelia, which means the arm and/or leg bones do not develop at all and the hands and/or feet are directly attached to the torso of the body.

Less severe cases may present symptoms where fingers are fused together or the long bones that form the arms and/or legs are greatly shortened. In addition, the bones in either the upper or lower legs or arms may be missing, resulting in a very short limb.

There are a variety of reasons why a limb may not develop normally in utero, so it is very important to rule out other causes before assuming phocomelia, a rare disorder, is the reason. Approximately 6 out of every 100,000 infants may present with a limb abnormality, but far fewer of these cases will be show to be directly linked to phocomelia.

Causes

While thalidomide was the primary cause in years past, the main known causes of phocomelia today relate to genetic mutations. There are two types of genetic mutations thought to cause phocomelia syndrome: heritable mutation through an autosomal recessive trait or a spontaneous (non-heritable) mutation.

When the cause is genetic, the person must receive a copy of the mutated gene from both parents in order to be at risk of developing phocomelia. Otherwise, if only one parent contributes the gene, the individual will be a non-affected genetic carrier of phocomelia. It is currently not known why some cases of phocomelia are relatively mild and others are quite severe.

Diagnosis & Tests

These are the tests most commonly used to detect phocomelia in the developing fetus after conception:

  • Ultrasound. Through the use of neonatal ultrasound, it is now possible to diagnose phocomelia as early as week 12 of a woman's pregnancy. However, if the symptoms are subtle or minor at this stage, the ultrasound may not be able to detect the abnormalities.
  • Amniocentesis. A more accurate neonatal test is called amniocentesis. In this test, amniotic fluid is taken from the amniotic sac and tested. Unfortunately, there is some risk that amniocentesis may cause a miscarriage, so typically this test will only be ordered after a blood test delivers what is called a "triple test" abnormality. Amniocentesis is performed with the aid of ultrasound and can be done as early as week 11 of a woman's pregnancy if the need is there.

If neonatal testing is not performed, the method used to diagnosed phocomelia is presentation of symptoms at birth. Phocomelia will present as some level of limb deformity, which will be visible immediately at birth.

Treatment & Therapy

Once phocomelia has been confirmed, either through neonatal tests or at birth via a visual inspection of the infant, the treatment stage can begin. Since there is currently no way to rebuild missing or deformed limbs, treatment focuses on use of prosthetics along with lifestyle modification to maximize independence and quality of life.

There are some surgical options that are being successfully used to offer phocomelia patients greater mobility and independence, including bone grafting and use of myoelectric prosthetic limbs, which can be operated without any need for wires or cords. These limbs are actually wired to the muscles, and the individual is then trained to operate them. Use of these newer prostheses can be implemented even if there is very little limb left because they are wired directly to the muscles responsible for moving that limb.

While treatment is typically planned as soon as phocomelia has been definitively diagnosed, often the actual treatments cannot be implemented until the infant is older. In the meantime, the infant can begin receiving occupational therapy and physical therapy to learn the best way to move and navigate from a young age.

Prevention & Prophylaxis

Currently there is no known method of totally preventing phocomelia. For phocomelia that is heritable, parental genetic testing can predict the risk of passing it on to an unborn child. However, this will not work if the mutation is spontaneous.

Since the drug thalidomide is still being prescribed for other conditions such as leprosy and cancer, it is critical for any woman who is pregnant or thinking about becoming pregnant to inform the treating physician of this immediately.