The incidence of acquired AA is about 2 per million population per year in North America and Europe.[1]International Agranulocytosis and Aplastic Anemia Study Group. Incidence of aplastic anemia: the relevance of diagnostic criteria. Blood. 1987 Dec;70(6):1718-21.
http://www.ncbi.nlm.nih.gov/pubmed/3676511?tool=bestpractice.com
[9]Vaht K, Göransson M, Carlson K, et al. Incidence and outcome of acquired aplastic anemia: real-world data from patients diagnosed in Sweden from 2000-2011. Haematologica. 2017 Oct;102(10):1683-90.
http://www.haematologica.org/content/102/10/1683.long
http://www.ncbi.nlm.nih.gov/pubmed/28751565?tool=bestpractice.com
There is no sex imbalance. Patients can be affected at any age, although there is a biphasic age distribution with peaks from 10 to 25 years and >60 years.[10]Brodsky RA, Jones RJ. Aplastic anaemia. Lancet. 2005 May 7-13;365(9471):1647-56.
http://www.ncbi.nlm.nih.gov/pubmed/15885298?tool=bestpractice.com
The incidence of AA is reported to be 2 to 3 times greater in East Asia than in North America and Europe.[11]Young NS, Kaufman DW. The epidemiology of acquired aplastic anemia. Haematologica. 2008 Apr;93(4):489-92.
http://www.haematologica.org/content/93/4/489.long
http://www.ncbi.nlm.nih.gov/pubmed/18379007?tool=bestpractice.com
Possible reasons include increased exposure to drugs, toxins, and viruses; higher incidence of inherited AA or genetic predisposition, such as polymorphisms of tumour necrosis factor-alpha, interferon-gamma, and drug detoxifying enzymes (GSTM1 and GSTT1); and regional variations in the diagnostic criteria and classification of AA and other bone marrow disorders (e.g., hypoplastic myelodysplastic syndrome).[3]Young NS. Acquired aplastic anemia. Ann Intern Med. 2002 Apr 2;136(7):534-46.
http://annals.org/article.aspx?articleid=715207
http://www.ncbi.nlm.nih.gov/pubmed/11926789?tool=bestpractice.com
[12]Kojima S. Why is the incidence of aplastic anemia higher in Asia? Expert Rev Hematol. 2017 Apr;10(4):277-9.
https://www.tandfonline.com/doi/full/10.1080/17474086.2017.1302797
http://www.ncbi.nlm.nih.gov/pubmed/28264622?tool=bestpractice.com
Congenital AA was previously considered rare, but an increasing number of patients with presumed acquired AA are now being diagnosed with germline mutations (e.g., inherited telomeropathies) with the use of next-generation sequencing.[5]Townsley DM, Dumitriu B, Young NS. Bone marrow failure and the telomeropathies. Blood. 2014 Oct 30;124(18):2775-83.
http://www.bloodjournal.org/content/124/18/2775.long?sso-checked=true
http://www.ncbi.nlm.nih.gov/pubmed/25237198?tool=bestpractice.com
[13]Liang J, Yagasaki H, Kamachi Y, et al. Mutations in telomerase catalytic protein in Japanese children with aplastic anemia. Haematologica. 2006 May;91(5):656-8.
http://www.haematologica.org/content/91/5/656.long
http://www.ncbi.nlm.nih.gov/pubmed/16627250?tool=bestpractice.com
[14]Marsh JCW, Gutierrez-Rodrigues F, Cooper J, et al. Heterozygous RTEL1 variants in bone marrow failure and myeloid neoplasms. Blood Adv. 2018 Jan 4;2(1):36-48.
http://www.bloodadvances.org/content/2/1/36?sso-checked=true
http://www.ncbi.nlm.nih.gov/pubmed/29344583?tool=bestpractice.com
[15]Cardoso SR, Ellison ACM, Walne AJ, et al. Myelodysplasia and liver disease extend the spectrum of RTEL1 related telomeropathies. Haematologica. 2017 Aug;102(8):e293-6.
http://www.haematologica.org/content/102/8/e293.long
http://www.ncbi.nlm.nih.gov/pubmed/28495916?tool=bestpractice.com
[16]Bluteau O, Sebert M, Leblanc T, et al. A landscape of germ line mutations in a cohort of inherited bone marrow failure patients. Blood. 2018 Feb 15;131(7):717-32.
http://www.ncbi.nlm.nih.gov/pubmed/29146883?tool=bestpractice.com
One of the most common congenital causes is Fanconi anaemia.[17]Dufour C. How I manage patients with Fanconi anaemia. Br J Haematol. 2017 Jul;178(1):32-47.
http://www.ncbi.nlm.nih.gov/pubmed/28474441?tool=bestpractice.com
Patients with congenital AA most commonly present in early childhood, but can sometimes present as young adults and occasionally in their 30s or 40s, and very rarely, in their 50s.