Incidence, Geographic and Age Distribution

The International AA and Agranulocytosis Study (IAAAS) was con ducted in Europe and Israel from 1980 to 1984. This study was performed prospectively and applied strict case definition to pathologically confirmed cases. Using stringent criteria, the overall annual incidence of AA was 2 cases per 1 million people. In Asia, similar methodology was applied by Thai investigators to determine a higher annual incidence, 4.0 cases per 1 million people in Bangkok, and 5.6 cases per 1 million people in the northeastern Thai province of Khonkaen. In general, from published, hospital-based series, per sonal communications, and first-hand observations, AA appears more prevalent in less developed regions of the world. There are no major sex or racial differences in the occurrence of AA. AA is a disease of the young (Fig. 1). Most patients present between 15 and 25 years of age or older than 60 years of age.

Fig1. DISTRIBUTION OF APLASTIC ANEMIA BY AGE. For patients at the University of Washington (Seattle), a major transplantation center, the age given is at the time of first treatment. For the patients at the National Institutes of Health (NIH), where immunosuppressive therapy is offered, the age given is at the time of diagnostic bone marrow biopsy. Acute disease is defined as less than 3 months between diagnosis and presentation at NIH, and chronic disease is defined as more than 3 months. (Seattle statistics are courtesy of Rainer Storb, University of Washington.)

Epidemiologic Clues to Causality

Population-based studies have investigated possible causal associations. Drugs are implicated in approximately 25% of the cases of AA in the West; while in Thailand, AA was attributed to drug exposure in only approximately 15% of the cases. There are associations with chemical exposures, exposures to viruses, hepatitis, and occupation. There is evidence that geographic variation in the incidence of AA might result from environmental causes and also genetic predispositions.

Genetic Aspects

In children and young adults, acquired AA should be distinguished from the main inherited forms of BM failure, Fanconi anemia (FA) and telomere biology disease (TBD). Identification of constitutional AA has important therapeutic implications. Patients with FA and TBD can lack typical physical anomalies, and the pan cytopenia can develop long after childhood, mimicking acquired dis ease. Genomic approaches to the study of AA are likely to uncover other genetic contributions to susceptibility to BM failure.

A few histocompatibility types have also been associated with AA, most consistently human leukocyte antigen (HLA)-DR2. HLA-DR subtypes predicted response to immunosuppressive therapy in a large cohort of US AA patients, in which HLA-DR15 was associated with the presence of a paroxysmal nocturnal hemoglobinuria (PNH) clone and responsiveness to immunosuppression. Genetic predisposition may be responsible for some idiosyncratic reactions to drugs and chemicals leading to the development of AA. Polymorphisms in cytokine genes, associated with an increased immune response, are also more prevalent in AA. Genome-wide transcriptional analysis of T and natural killer cells from AA patients has implicated pathologic expression of components of innate immunity, including Toll-like receptors.

اخر الاخبار

اخبار العتبة العباسية المقدسة

المجمع العلمي يقيم مهرجانًا بذكرى الولادات الشعبانية في بغداد

معهد القرآن الكريم النسوي يباشر استعداداته لإقامة مهرجان السقاء القرآني السنوي الخامس

بالتعاون مع جامعة ستانفورد.. جامعة الكفيل تعتمد منهجًا متطورًا لطب الطوارئ

سماحة السيد الصافي يستقبل وفد شركة (سيتي فارما) الباكستانية المختصة في الأدوية

المزيد

الآخبار الصحية

اللحظات الأخيرة قبل الموت.. هذا هو تسلسل "فقدان الحواس"

وخز الأطراف وضعف الذاكرة.. علامات على نقص فيتامين هام

عادة صباحية بسيطة.. تأثيرها قد يحسن ضغط الدم

عادات يومية تدمر قلبك بصمت.. خبراء يطلقون التحذير

المزيد

الآخبار التكنلوجية

الذكاء الاصطناعي يفك لغز آثار أقدام الديناصورات

القمر أولا.."سبيس إكس" تؤجل خططها الخاصة بالرحلات إلى المريخ

الذكور أم الإناث؟ دراسة "تنسف الشائع" بشأن التوحد

خبير يكشف عن اقتراب العلماء من فك شفرات "لغات الحيوانات" !

المزيد

مواضيع ذات صلة

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Clinical Features of Hyper- and Hypothyroidism

Clinical Associations of Aplastic Anemia

Typical and Atypical Presentations of Aplastic Anemia

Pathophysiologic Pathways Leading to Aplastic anemia

Pneumonia

Bronchitis

Pathogenesis of the respiratory tract: Microorganism Factors

Pathogenesis of the respiratory tract: Host Factors

Clinical Manifestations of Bloodstream Infections

Definition of Sepsis

Types of Bloodstream Infections