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Krabbe Disease




Introduction

Krabbe disease is a rare, inherited, often fatal disorder affecting the central nervous system. The disease can affect muscle tone and movement, and cause vision and hearing loss, among other effects.

In most cases, Krabbe disease develops in babies before six months of age, although it can occur in older children and in adults.

Krabbe disease may be best known in the United States for the media attention it received when former professional football quarterback Jim Kelly raised awareness and research funds for the disorder, which had been diagnosed in his son, Hunter.

Treatment for Krabbe disease mainly involves approaches designed to ease symptoms.

Signs and symptoms

In the more common form of Krabbe disease, which develops in the first months of life, signs and symptoms often include:
  • Feeding difficulties.
  • Failure to thrive.
  • Fevers.
  • Vomiting.
These babies may also experience:
  • Extreme irritability.
  • Changes in muscle tone (limb and muscle stiffness, poor coordination of movements).
  • Seizures.
  • Progressive loss of hearing and sight.
  • Spasticity (presence of spasms or consistently increased muscle tone).
  • Mental deterioration.
Late-onset Krabbe disease.
When children have the late-onset form of the disease — which develops later in childhood or in adolescence — they may experience the signs and symptoms above, as well as other signs that may include:
  • Visual impairment progressing to blindness, which may be the initial sign.
  • Difficulty walking (called ataxia or gait disturbances).
  • Loss of manual dexterity.
As a general rule, the younger the age that Krabbe disease occurs, the more rapid its progression. Some people diagnosed during adolescence may have less-severe symptoms, with muscle weakness as a primary symptom. They may have no impairment of their cognitive abilities.

Causes

Krabbe disease is one of a group of genetic conditions called leukodystrophies. Doctors sometimes refer to Krabbe disease as globoid cell leukodystrophy — the globoid cells are storage cells that play a role in the disorder. The disease is named after the Danish neurologist who first reported infants with the condition in 1916.

The cause of Krabbe disease is a deficiency in an enzyme called galactocerebrosidase (GALC), which is essential for the maintenance of myelin — a fatty substance that insulates your nerve fibers.

A child needs to inherit an abnormal gene from each parent to trigger the disorder. Passing on the genes occurs in an inheritance pattern called autosomal recessive. Specifically, Krabbe disease has been linked to a defect in chromosome 14.

Treatment

There's no specific, proven treatment for Krabbe disease, nor is there a cure. Krabbe disease treatment is designed primarily to ease symptoms. For example, anticonvulsant medications may be used to manage the seizures associated with this disease. Other drugs may reduce the risk of vomiting.

Some older children with less-severe forms of the disease may benefit from physical therapy, which is intended to minimize deterioration of muscle tone. Some may also benefit from occupational therapy, in which they'll learn to achieve as much independence as possible — for example, learning to dress themselves, brush their teeth and feed themselves.

Some research indicates possible benefits associated with the use of bone marrow transplantation or cord blood transfusion as treatments for Krabbe disease:
  • Bone marrow transplantation. Adult bone marrow — the sponge-like material present in bones — has been used to replace a child's own bone marrow in Krabbe disease. This procedure is called hematopoietic stem cell transplantation. It appears to provide benefits primarily to older children who have less-severe forms of the disease, or to infants diagnosed at birth.
    For other children — particularly infants who have already developed symptoms — this treatment does not appear to halt or slow progression of the disease in babies, nor has it shown success in a small number of cases in which treatment was carried out in fetuses diagnosed with the disease before birth.
    More research — including longer follow-up with more subjects — is needed to better determine the role of this approach and the reasons for its possible benefits. Early research suggests that it may provide functional enzymes to replace those that had been impaired. Clinical trials of hematopoietic stem cell transplantation for presymptomatic, affected infants and older patients with mild symptoms have begun.
  • Cord blood transfusion. A transfusion of blood stem cells, obtained from the umbilical cord of unrelated donors, has reduced neurological symptoms in some infants with Krabbe disease.
    In small studies, doctors have transfused healthy donor cells with normal enzyme (GALC) activity into babies with Krabbe disease who have not yet developed symptoms. This treatment has stimulated normal development of myelin in these babies. Babies treated within the first two months of life, before symptoms appear, maintained normal hearing and vision, although there was a subsequent deterioration of motor skills such as walking or picking up objects. One study of the use of umbilical cord cells also showed promising findings in fetuses who had been diagnosed prenatally.
    This approach may prove to be most appropriate when a suitable transplant donor, such as a family member, is not readily available; matched cord blood may be found more readily.
In the future, gene therapy could play a role in the treatment of Krabbe disease, in which a functional gene is delivered via a virus to the cells or tissue, replacing the abnormal gene that is responsible for the disorder.


Information obtained from National Institute of Health
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