krabbe disease a case study

Krabbe Disease: A Rare and Rapidly Progressing Genetic Condition

Krabbe disease is a rare and rapidly progressing genetic condition that removes myelin, a protective layer on the surface of the nervous system. This disease was named after Knud Haraldsen Krabbe, a neurologist who pioneered the classification of the condition in the early 1900s. This disease mostly impacts children under the age of two, affecting about one out of every 100,000 children. Children with this condition experience sudden development of signs and symptoms by the age of six months (Wenger, Rafi & Luzi, 2016). It is important to note that this condition has no cure, but recovery focuses on controlled and compassionate care for patients. The children with this disease hardly make it celebrate their 2nd birthday.

Mode of Inheritance

This disease is inherited from the parents; both parents of a child with Krabbe disease usually are carriers; this means that both parents each carry one mutated copy of the gene that is responsible for causing the disease. In most cases, carriers depict no symptom or signs of the condition. Fertilization entails an X chromosome from the mother and the Y or X chromosome from the father. In a single fertilization when both parents are carriers of an abnormal gene, it can either be transferred to the children or the children can also become carriers, or still, the child will not have the abnormal genes (Wenger, Rafi & Luzi, 2016). Therefore inheritance of the condition happens when two parents who are both carriers of an autosomal recessive disease have children, each of the children is at a 25% risk of having the disease. The chances of being a carrier just like the parents are higher at 50%. The remaining percentage of 25% is a chance of neither having the condition nor not being a carrier of the disease (Marques, Willems, Herrera, Florea, Scheij, Ottenhoff & Biela-Banas, 2017).

Clinical Description

The Krabble disease develops at different ages. The first stage is characterized by hyperactivity and on and off fevers. Most children develop symptoms in the early first six months of age. On other cases, children may develop the symptoms at a later stage in childhood and even adulthood. The disease can be characterized by the following signs and symptoms; children with this disorder have delayed developmental milestones. The mortar skills for are delayed and the child is not able to sit correctly by the age of five (Isakova, Baker, Dufour & Phinney, 2017). They cannot even move their hand voluntarily. On the other side, the children with this disorder are highly irritable and sensitive to loud sounds. The children excessively throw tantrums and are always crying most of the time. Everything around them seems to be disgusting and irritating. A child with this disorder has no balance especially the head control, therefore he or she cannot stay upright or lift up his head for a minute; the head often falls to the side which means that they continuously need support to remain upright during feeding; it is for this reason that food becomes very difficult. In general, a person with this condition has delayed developmental milestones such as delayed movement. On the other hand, such a person is always irritated by almost everything and will still be mood less most of the time. On the other side, they are often sensitive especially to sounds which make them easily irritated (Marques, Willems, Herrera, Florea, Scheij, Ottenhoff & Biela-Banas, 2017).

Treatment

As mentioned earlier, this disorder has no cure, and it is typically managed through supportive care to the patients. After the diagnosis of a person, the very first treatment is focused on the symptoms present. In a case where the patient is vomiting and doesn’t feed, various medications are given to relieve the pain. Secondly, different therapies are provided to improve the state of the patient. It includes physical, respiratory and even speech therapies (Wenger, Rafi & Luzi, 2016). Physical therapy has been used to increase the masculine activities through circulation and toning of the muscles; this is in a bid to rectify the developmental delays. Speech therapy also improves the speech development of the patient hence improving the condition. Recent studies have suggested that stem cell transplants (the umbilical cord blood stem cells) can be efficiently used to treat the disorder in children who have not developed symptoms and in older people with mild symptoms. This type of treatment reduces the rate at which the disease progresses to adverse stages (Isakova, Baker, Dufour & Phinney, 2017).

Genomics

The GALC gene is the only gene responsible for causing this disease. The GALC gene gives directions for the production of an enzyme known as galactosylceramidase via a process known as hydrolysis. This enzyme breaks down galactolipid fats that are typically found in the brain and in the kidneys. This protein is one of the essential components of myelin; the protective coating on the nerve cells. Therefore the mutation in this gene is the leading causes of Krabbe disease. The mutations cause the deficiency of galactosylceramidase enzyme which in turn leads to loss of myelin. The absence of myelin causes the body parts not to function commonly hence leading to the Krabble disease symptoms and signs. Human beings have 46 chromosomes in every cell; they are divided into two pairs of 23 each. Two copies of chromosome 14 each inherited from each parent. Therefore its precise chromosomal location is 14.

Population Genetics

This disease affects 1 in 100,000 children in every country. It majorly affects children less than a year. This condition mainly affects people of Scandinavian descent. On the other hand, the disease can affect just anyone as long as the parents were carriers of the defective gene. In some populations the condition is low such as the Druze Community in Israel. In the Jewish community, there has been no case recorded (Isakova, Baker, Dufour & Phinney, 2017). Patients in the adult stage are more in southern Europe whereas infantile examples are high in Nordic countries.

Detection

It is detected through conducting a skin tissue biopsy or a blood test. In the laboratory, the sample is tested for GALC enzyme activity; if the action is low, then there is a likelihood of the presence of the Krabbe disease. An MRI scan on the brain can also be done to detect the abnormalities present. An eye examination can also be conducted to check the state of the optic nerve (Bongarzone, Escolar, Gray, Kafri, Vite & Sands, M. S. (2016).

Conclusion

There are three animal models that have been used in the research of the Krabbe disease. A mouse model, a dog model, and a monkey model. The mouse model carries similar genetic defects that are found in human patients with the disease. The affected mice often develop signs equivalent to Krabble disease and if untreated die by 35 or more days. Transplantation of bone marrow increases the days of the mice.

References

Bongarzone, E. R., Escolar, M. L., Gray, S. J., Kafri, T., Vite, C. H., & Sands, M. S. (2016). Insights into the Pathogenesis and Treatment of Krabbe Disease. Pediatric endocrinology reviews: PER, 13, 689-696.

Isakova, I. A., Baker, K. C., Dufour, J., & Phinney, D. G. (2017). Mesenchymal Stem Cells Yield Transient Improvements in Motor Function in an Infant Rhesus Macaque with Severe Early‐Onset Krabbe Disease. Stem cells translational medicine, 6(1), 99-109.

Isakova, I. A., Baker, K. C., Dufour, J., & Phinney, D. G. (2017). Mesenchymal Stem Cells Yield Transient Improvements in Motor Function in an Infant Rhesus Macaque with Severe Early‐Onset Krabbe Disease. Stem cells translational medicine, 6(1), 99-109.

Marques, A. R., Willems, L. I., Herrera Moro, D., Florea, B. I., Scheij, S., Ottenhoff, R., ... & Biela‐Banas, A. (2017). A Specific Activity‐Based Probe to Monitor Family GH59 Galactosylceramidase, the Enzyme Deficient in Krabbe Disease. ChemBioChem, 18(4), 402-412.

Wasserstein, M. P., Andriola, M., Arnold, G., Aron, A., Duffner, P., Erbe, R. W., ... & Kay, D. M. (2016). Clinical outcomes of children with abnormal newborn screening results for Krabbe disease in New York State. Genetics in Medicine, 18(12), 1235-1243.

Wenger, D. A., Rafi, M. A., & Luzi, P. (2016). Krabbe disease: One Hundred years from the bedside to the bench to the bedside. Journal of neuroscience research, 94(11), 982-989.