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Reticular Dysgenesis (RD)[edit]
Reticular dysgenesis (RD) is a rare, inherited autosomal recessive disease that results in immunodeficiency.[1] Individuals with RD have mutations in both copies of the AK2 gene.[1] Mutations in this gene lead to absence of AK2 protein.[2] AK2 protein allows hematopoietic stem cells to differentiate and proliferate.[2] Hematopoietic stem cells give rise to blood cells.[2]
Differentiation and proliferation of hematopoietic stem cells require a lot of energy and this energy is supplied by the mitochondria.[2] The energy metabolism of mitochondria is regulated by the AK2 protein.[2] If there is a mutation in the protein, that means that the mitochondria metabolism most likely will be altered and will not be able to provide enough energy to the hematopoietic stem cells.[2] As a result, hematopoietic stem cells will not be able to differentiate or proliferate.[2]
The immune system consists of specialized cells that work together to fight off bacteria, fungi and viruses.[3] These cells include T lymphocytes (T cells), that primarily mediate the immune system, B lymphocytes (B cells) and Natural Killer cells.[3] Patients with RD have a genetic defect that affects the T cells and at least one other type of immune cell.[4] Since more than one type of immune cell is affected, this disease is classified as a severe combined immunodeficiency disease (SCID).[3] A weakened immune system leaves patients susceptible to different kinds of infection. Commonly, patients who are diagnosed with RD also have bacterial sepsis and/or pneumonia. [4]
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Signs and symptoms[edit]
| Signs and Symptoms | Approximate Number of Patients Affected |
|---|---|
| Abnormality of mitochondria metabolism | 90% |
| Abnormality of Neutrophils | 90% |
| Anemia | 90% |
| Aplasia/Hypoplasia of the thymus | 90% |
| Cellular immunodeficiency | 90% |
| Decreased antibody level in blood | 90% |
| Diarrhea | 90% |
| Hearing Impairment | 90% |
| Recurrent respiratory infection | 90% |
| Sepsis | 90% |
| Abnormality of temperature regulation | 50% |
| Malabsorption | 50% |
| Weight Loss | 50% |
| Dehydration | 7.5% |
| Skin rash | 7.5% |
| Skin Ulcer | 7.5% |
Risk Factors[edit]
- Condition follows an autosomal recessive pattern[6]
Diagnosis[edit]
Health professionals must look at a person's history, symptoms, physical exam and laboratory test in order to make a diagnosis. If the results show patients with low levels of lymphocytes, absence of granulocytes or absence of thymus then the patient may be suspected to have RD.[4]
Prognosis[edit]
The survival range is estimated to be 3 days to 17 weeks without treatment.[7] Patients die due to bacterial or viral infections.[7] Aggressive treatment with antibiotics is required and bone marrow transplant is common.[7] Patients undergoing bone marrow transplant, specifically from a matched sibling, have a higher 5 year survival rate than those receiving a transplant from other donors.[8]
Treatment[edit]
RD can only be treated temporarily through Hematopoietic stem cell transplantation (HSCT) and Cytokine Therapy. [4][7][9]
Hematopoietic Stem Cell Transplantation[edit]
Transplantation of stem cells are taken from the bone marrow, peripheral blood or umbilical cord of healthy, matched donors.[8] Hematopoietic Stem Cell Transplantation (HSCT) involves intravenous infusion of stem cells to those who have either a damaged bone marrow or defective immune system. [4][8] Transplantation is a simple process. Bone marrow product is infused through a central vein over a period of several hours.[8] The hematopoietic cells are able to go to the bone marrow through tracking mechanisms.[8] Patients who suffer from RD will now have more stem cells that can differentiate into immune cells.
Cytokine Therapy[edit]
Recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) can be used as a temporary cure.[7] GM-CSF stimulates production of white blood cells.[7] This cure is commonly used in patients who are awaiting bone marrow transplantation[7]. Response to this cure can vary. [7] Those with a more severe combined immunodeficiency may have no response to this therapy.[7]
Research[edit]
Gene Therapy[edit]
Gene therapy is a relatively new concept in the field of SCID.[10] This therapy is currently undergoing clinical trial and has cured a small number of children suffering from X-linked SCID and recessive allele SCID.[10] Gene therapy aims to correct the underlying genetic abnormality in SCID.[10] In the case of RD, the genetic abnormality would be AK2 malfunction.[2] Stem cells are taken from an affected child's blood or bone marrow.[10] Then in laboratory conditions the stem cells are manipulated and corrected with gene technology.[10] They are then injected back into the patient.[10] Similarly, in bone transplant, stem cells are able to find their way back through tracking mechanisms. [8][10]
References[edit]
- ^ a b Pannicke, Ulrich; Hönig, Manfred; Hess, Isabell; Friesen, Claudia; Holzmann, Karlheinz; Rump, Eva-Maria; Barth, Thomas F; Rojewski, Markus T; Schulz, Ansgar. "Reticular dysgenesis (aleukocytosis) is caused by mutations in the gene encoding mitochondrial adenylate kinase 2". Nature Genetics. 41 (1): 101–105. doi:10.1038/ng.265.
- ^ a b c d e f g h Six, E.; Lagresle-Peyrou, C.; Susini, S.; De Chappedelaine, C.; Sigrist, N.; Sadek, H.; Chouteau, M.; Cagnard, N.; Fontenay, M. (2015-08-13). "AK2 deficiency compromises the mitochondrial energy metabolism required for differentiation of human neutrophil and lymphoid lineages". Cell Death & Disease. 6 (8): e1856. doi:10.1038/cddis.2015.211. PMC 4558504. PMID 26270350.
- ^ a b c "The Immune System and Primary Immunodeficiency | Immune Deficiency Foundation". primaryimmune.org. Retrieved 2016-11-20.
- ^ a b c d e Bertrand, Y.; Müller, S. M.; Casanova, J. L.; Morgan, G.; Fischer, A.; Friedrich, W. (2002-05-01). "Reticular dysgenesis: HLA non-identical bone marrow transplants in a series of 10 patients". Bone Marrow Transplantation. 29 (9): 759–762. doi:10.1038/sj.bmt.1703531. ISSN 0268-3369. PMID 12040473.
- ^ "Reticular dysgenesis". GARD.
- ^ a b c "Severe Combined Immunodeficiency - NORD (National Organization for Rare Disorders)". NORD (National Organization for Rare Disorders). Retrieved 2016-11-20.
- ^ a b c d e f g h i Calhoun, Christensen, DA, RD (1998). "Recent advances in the pathogenesis and treatment of nonimmune neutropenias in the neonate". Current Opinion in Hematology. 5: 37–41.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b c d e f Perumbeti, Ajay. "Hematopoietic Stem Cell Transplantation". Medscape.
- ^ Scheinfeld, Noah. "Intravenous Immunoglobulin". Intravenous Immunoglobulin. Medscape.
- ^ a b c d e f g "Severe combined immunodeficiency (SCID)". Retrieved 2016-11-20.