Krabbe, or also called globoid cell leukodystrophy or galactosylceramide lipidosis, is a disease that affects the myelin layer of the nerve cells in the brain and the whole nervous system. In other words, it is a degenerative disorder that destroys the protective layer of the nerve cells. It is rare. Usually 1 out of 100,000 people is affected. Unfortunately, it is often fatal disease for which there is no cure. It is an inherited disorder named after the Danish neurologist Knud Haraldsen Krabbe.
Generally, symptoms appear in babies when they are younger than 6 months and result in death by the time they turn 2. If the disease develops among older children or adults the progress varies a lot.
As there is no cure for Krabbe disease, the treatment consists of care and support. It is possible a stem cell transplantation to be made which has proven to be somewhat successful in young kids that are treated before the appearance of symptoms and in some cases among older children and adults as well.
Normally, the symptoms of Krabbe disease appear early, in the very beginning of the course of the disease. They begin to show gradually, but get worse progressively. The most common symptoms among infants are:
- Crying without any explicable reason
- Problematic feeding
- Fever without infection
- Great irritability
- Deteriorations of awareness
- Loss of head control
- Muscle spasms
- Vomiting frequently
The symptoms become more severe with the progress of the disease and they can be:
- Stiff posture
- Constricted muscles
- Bad hearing that progresses to complete loss of the ability to hear
- Progressive loss of the sight
- Progressive loss of the capability to swallow or and breathe
- Loss of developmental capabilities
Among older children and adults the symptoms develop later and differ a lot. Some of the symptoms are:
- Loss of vision
- Loss of control of body movements ( for instance: having difficulties to walk or having problems with manual dexterity; i.e. experiencing ataxia)
- Weak muscles
- Decline of the thinking skills
Sometimes, adolescents or adults suffering from this disorder can only experience muscle weakness primarily and have no impaired thinking skills.
Generally, the sooner the Krabbe disease appears, the faster it develops and the greater is the possibility to result in death.
The Krabbe disease occurs when a child inherits two mutated copies of the gene (one from each parent). A gene is responsible for a kind of draft for protein production. If there is an error, the protein product may not work as it should. When it comes to the Krabbe disease, two mutated copies of a certain gene produce little or do not produce at all an enzyme called galactocerebrosidase (GALC). This enzyme is responsible for breakage of particular substances in the lysosome. In Krabbe disease, there is shortage of GALC that brings to accumulation of fats called galactolipids that produce and maintain the protective layer of the nerve cells. Abundance of galactolipids has a toxic effect. Some galactolipid cause the cells that form the myelin to self-destruct.
Others, however, are taken by microglia. The cleaning of excessive galactolipids is a process during which trnasforms the helpful cells into abnormal cells that are toxic. These cells are called globoid cells and they promote the damaging of the myelin. The demyelination i.e. loss of myelin stops cells form sending and receiving messages.
If the parents have one mutated copy of the gene, the risk for the child is:
- 25% of having the disease if two mutated copies are inherited
- 50% that the child will be only a carrier having inherited only one mutated copy that doesn’t result in having the disease
- 25% chance of inheriting two normal gene copies
Parents that are carriers of a GALC gene mutation, have history of the disease in the family, or already have a child diagnosed with Krabbe disease should consider genetic testing.
Most of the infants who develop this disorder die by the age of two usually from failure of the respiratory system or very weak muscles that result in immobility. Teenagers and older children have a life-expectancy between two and seven years after diagnosed with the Krabbe disease. Some of the complications that may be expected are: infections, respiratory problems, disability and vegetative state in the later stages of the disease.
The treatment for Krabbe disease means managing the symptoms and providing supportive care, as there is no cure for the disorder.
Measures that can be taken are:
- Nutritional support (gastric tube)
- Physical therapies in order deteriorating of the muscles to be diminished
- Pills that will ease the muscle irritability
- Anticonvulsant medications that manage the seizures
If the disease has taken less severe form (as it is the case among older children or adults), the intervention measures can be physical and occupational therapies so that greater independence with daily activities can be achieved and the deteriorating of the muscles can be minimized.
Another treatment that can be considered is stem cell transplantation.