Many patients with aplastic anemia also have clones of cells characteristic of paroxysmal nocturnal hemoglobinuria (PNH), a rare disease that causes anemia with thrombocytopenia and/or thrombosis and is sometimes referred to as AA/PNH. Occasionally PNH dominates over time, with the major manifestation of intravascular hemolysis. The overlap of AA and PNH has been speculated to be an escape mechanism by the bone marrow against destruction by the immune system. Flow cytometry testing is performed regularly in people with previous aplastic anemia to monitor for the development of PNH. Prognosis
Untreated, severe aplastic anemia has a high risk of death. Modern treatment produces a five-year survival rate that exceeds 85%, with younger age associated with higher survival.Survival rates for stem cell transplants vary depending on the age and availability of a well-matched donor. They are better for patients who have donors that are matched siblings and worse for patients who receive their marrow from unrelated donors. Overall, the five-year survival rate is higher than 75% among recipients of blood marrow transplantation.Older people (who are generally too frail to undergo bone marrow transplants) and people who are unable to find a good bone marrow match have five-year survival rates of up to 35% when undergoing immune suppression.Relapses are common. Relapse following ATG/ciclosporin use can sometimes be treated with a repeated course of therapy. In addition, 10–15% of severe aplastic anemia cases evolve into myelodysplastic syndrome and leukemia. According to one study, 15.9% of children who responded to immunosuppressive therapy eventually relapsed.Milder disease may resolve on its own.
The severity of each case is determined by the number of cells with this extra copy. Some characteristics of individuals with this condition are cardiac abnormalities, growth retardation, mental delay, etc. Complete trisomy 22,  in contrast with mosaic trisomy 22,  is characterized by an extra copy of chromosome 22 found in each cell of the body of the affected individual. As of 2014, 29 live-born human cases have been reported, with all of them dying before the age of 12 months. References
Further reading
Mokate T, Leask K, Mehta S,  et al. (2006). "Non-mosaic trisomy 22: a report of 2 cases". Prenat. Diagn. 26 (10): 962–5. doi:10.1002/pd.1537. PMID 16906599. S2CID 43499352. External links

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