stasi.qxp 15/2/08 5:04 pm Page 62
Infection in Haematology
Helicobacter pylori and Idiopathic Thrombocytopenic Purpura –
Where Do We Stand?
a report by
Roberto Stasi
Department of Medical Sciences, Ospedale Regina Apostolorum, Albano Laziale, Rome
Helicobacter pylori is a microaerophilic, Gram-negative, spiral-shaped, Table 1 reports the prevalence of H. pylori infection in adults with ITP from
flagellated bacterium that colonises the mucous layer of the human 21 case series (studies including at least 15 cases) identified in a PUBMED
stomach.
1
It has been causally linked with a diverse spectrum of search. The method of detection in these studies was the 13-carbon (C)
gastrointestinal disorders, including gastritis, peptic ulcer disease, urea breath test. Most studies were conducted in Italy or Japan, where the
non-ulcer dyspepsia, gastric adenocarcinoma and mucosa-associated H. pylori rate in the middle-aged adult general population is around
lymphoid-tissue lymphoma.
2
Several investigators have studied 70%.
7,8
A low prevalence of H. pylori infection was found in 74
whether H. pylori causes non-digestive diseases, but these North American patients.
9
This was not dissimilar from that observed in a
associations, if any, are uncertain.
3
healthy American Caucasian population.
6
Using serological tests, Michel et
al. recorded a low prevalence (29%) of H. pylori infection in 51 adult ITP
The relationship between H. pylori infection and idiopathic patients of French Caucasian origin; the same rate of infection was found
thrombocytopenic purpura (ITP) has been investigated since 1998, when in control subjects.
10
These findings suggest that the prevalence of
an Italian group reported a significant increase of the platelet count in H. pylori infection in adult ITP patients may not differ from that of the
eight of the 11 ITP patients in whom the bacterium was eradicated.
4
general healthy population when matched for age and geographical area.
However, subsequent reports have produced inconsistent results. Most of
these studies involved a relatively small number of patients, the median The prevalence of H. pylori in children with ITP also varies widely among
observation following eradication was often less than one year and the different populations. H. pylori infection was not detected in any of 17
effects of prior therapies were unclear. In addition, studies usually paediatric patients with ITP in a Finnish population.
11
In contrast, 11 of
included patients with mild thrombocytopenia who would not ordinarily 35 (31%) Turkish children were shown to have an H. pylori infection as
have been treated. Therefore, the effects of H. pylori eradication in the documented by a positive 13C urea breath test.
12
A study from Japan
management of patients with ITP have remained undetermined. The aim reported the presence of H. pylori infection in two of 10 children.
13
of this article is to summarise the current evidence linking H. pylori H. pylori infection was detected in nine of 22 children (41%) from
infection to ITP, and to provide practical guidelines for H. pylori infection northern Taiwan.
14
detection and management.
Mechanisms of Helicobacter pylori-induced
Epidemiology of Helicobacter pylori Infection Thrombocytopenia
The seroprevalence of H. pylori infection in otherwise healthy individuals Although clinical studies suggest the involvement of H. pylori, little is known
varies greatly between countries and increases with age.
2
Adults from about the pathogenesis of H. pylori-associated ITP. Many hypotheses have
developing countries show a prevalence approaching 80%, whereas been advanced during the last few years about the mechanisms by which
rates of <60% are seen in developed countries. This rate is lower (<10%) H. pylori may cause ITP. One of them is molecular mimicry, according to
in children below 10 years of age. In an adult cohort from the US, positive which H. pylori could induce antibody production in response to antigens
H. pylori serology ranged from 17% for persons aged between 20 and that cross-react against various platelet glycoprotein antigens.
29 years to 57% for individuals aged ≥70 years.
5
Within the US a higher
frequency of infection has been demonstrated in non-Hispanic blacks and The possible role of cytotoxin-associated antigen A (CagA)-positive strains
Mexican-Americans.
5,6
as a pathogenic candidate for ITP was recognised in two recent molecular
studies. The first showed a decline in platelet-associated immunoglobulin
Roberto Stasi has held a position at the Department of
G in ITP patients after the eradication of H. pylori infection, as well as the
Medical Sciences of the Regina Apostolorum Hospital of existence of a molecular mimicry between those antibodies and the CagA
Albano Laziale in Rome since 1995. Since 1990, he has been
protein.
15
The second study demonstrated that CagA antibodies
working at the outpatient clinic of the Division of
Haematology of Saint Eugenio Hospital, Rome. His current
cross-react with a peptide specifically expressed by platelets of patients
areas of research include the investigation of the role of
with ITP.
16
This study, as well as supporting an association between CagA
Helicobacter pylori in idiopathic thromboctyopenic purpura
and ITP, also proposed a possible explanation for the fact that ITP may
(ITP), the use of rituximab in ITP, treatment of myelodysplastic
syndromes with differentiating and antiapoptotic agents, the occur in only a small subset of patients infected by CagA-positive strains.
role of erythropoietic agents in cancer-related anaemia and treatment of metastatic colorectal
In this regard, it should be noted that most Japanese H. pylori strains are
cancer. He received his MD from the University of Rome’s ‘La Sapienza’ School of Medicine in
1987 and completed his post-doctoral studies at the same university, qualifying as a specialist in
positive for CagA
17
and have the intact Cag pathogenicity island (CPI).
18
haematology in July 1990. In 1999 he qualified as a specialist in oncology.
E: roberto.stasi@libero.it
Recently, Semple et al. demonstrated that in the presence of antiplatelet
antibodies, the lipopolysaccharide of Gram-negative bacteria can
62 © TOUCH BRIEFINGS 2007
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