What Is Phocomelia?

Phocomelia is a birth defect characterized by short upper and/or lower limbs. Where all four limbs are affected, it is known as tetra-phocomelia. The affected limbs appear to be shortened due to missing or underdeveloped bones. In some instances, children with phocomelia may have their limbs growing directly from the trunk.

Phocomelia is a rare defect. This wasn’t always the case, however. In the 1960s, thalidomide—a drug intended to treat anxiety and morning sickness—was recalled for being unsafe for use in pregnancy.

This discovery came at the expense of over 10,000 children born with birth defects around the world, phocomelia being a prominent anomaly caused by this drug. The 1960s also saw an uptick in reports of miscarriages.

However, despite being strictly regulated worldwide, incidents of thalidomide-induced phocomelia may arise in underdeveloped countries where this drug is still used as a treatment for leprosy. Phocomelia is reported to occur in 0.62 live births for every 100,000 deliveries.

Symptoms of Phocomelia

Phocomelia can appear in varying degrees of severity. The following symptoms may be observed:

• Nearly normal hand or foot
• Hand or feet directly attached to the trunk
• Absent or underdeveloped bones of the hand and leg such as the humerus or femur, radius or tibia, as well as ulna or fibula

Thalidomide-induced phocomelia may lead to facial problems which include irregular teeth numbers or spacing, small jaws, cleft palates and/or cleft lips as well as small noses.

This medication may also lead to shoulder and hip-joint damage, eye and ear damage. The vertebral column may display irregular spacing or a fusion of vertebrae in the lower spinal column. Thalidomide-induced phocomelia may also result in damage to internal organs as well as nerve and central nervous system (CNS) damage.

Types of Phocomelia

Phocomelia may be classified into three main types: complete, proximal, and distal.

• Complete Phocomelia: This is a condition in which the arm and forearm are missing. The hand is usually attached to the trunk in this form of phocomelia.
• Proximal Phocomelia: Here, the arm or thigh is absent. The forearm is attached to the trunk. 
• Distal Phocomelia: This may be observed where the forearm and legs are absent. Instead, the hand is attached to the humerus.

Causes of Phocomelia

While the exact cause of phocomelia is uncertain, this condition may be the result of a genetic inheritance. More commonly, it is a side-effect produced following maternal exposure to thalidomide.

In animals, thalidomide has been shown to prevent the formation of new blood vessels in the limb. It may also induce cell death, while also encouraging free radicals in limb tissue.

Thalidomide can cause the limb bud to be placed away from the point of attachment. It does this by reducing or blocking growth factors when the limb is being developed. This can also lead to the loss of proximal tissue, preventing the proper formation of the limb. The remaining tissue is then left to to grow from around the torso, where the hand is affected, or the femur where the leg is is involved. This can cause phocomelia.

Other Conditions Associated With Phocomelia

Where a person is experiencing phocomelia, there may be more than one option responsible for the diagnosis:

• Sporadic Phocomelia: This is a rare genetic disorder where phocomelia is inherited as a recessive trait. This condition may also result from a spontaneous mutation. 
• Roberts Syndrome: This is a rare disorder identifiable by malformations of the bone. In severe cases, the hands and feet may grow too close to the body, resulting in phocomelia.
• Holt-Hormam Syndrome: This condition, (also known as atrio-digital syndrome) affects the bones of the arms, hands, and shoulders. In some instances, the heart may also be impacted. People with this condition typically have at least one bone of the wrist that developed irregularly. Holt-Hormam syndrome is an autosomal dominant disorder.
• DK Phocomelia Syndrome: This is a rare disorder set apart by shortened or absent arms, encephalocele or sac-like projections of the brain, and the membranes that cover it through an opening in the skull. It may also produce brain abnormalities, urogenital anomalies, and a low number of platelets needed to clot blood.
• Schnitzel-Type Phocomelia: This is also known as Al-Awadi-Raas-Rothschild syndrome. It is marked by skeletal abnormalities from birth which include a missing fibula (the lower home of the leg) or a poorly developed pelvis. It may also feature differences in genitalia. Female subjects with this condition may have no uterus, while males may have undescended testis.
• CHILD Syndrome: This is also known as congenital hemidysplasia with ichthyosiform erythroderma and limb defects. This condition is caused by the mutation of the NSDHL gene which is required for the production of cholesterol. It is characterized by red and inflamed patches of skin, typically covered by flaky scales. It may also involve limb under development or absence. All of these symptoms usually occur on one side of the body, however, CHILD syndrome may also cause damage to internal organs.

Management of Phocomelia

To help with managing this condition, a first step is when a medical professional conducts a physical examination of the internal organs to rule out any abnormalities or to address any as quickly as is possible. This should be carried out by pediatric health care professionals.

In addition, to properly provide for the unique requirements of a child with phocomelia, parents, caregivers, and people with phocomelia alike are encouraged to seek professional therapy. It may be extremely helpful under any emotional and psychological strain of raising a differently-abled child.

A Word From Verywell

Phocomelia is a rare disorder marked by shortened limbs. Though it may be caused by a variety of elements, it does provide challenges that the person with the condition will face throughout their lives. To ensure your child is getting the proper care, seeking therapy can provide necessary information, as well as the emotional support needed to cope with the condition.