Perforin gene mutations in patients with acquired aplastic anemia

Hematology Branch, National Heart, Lung, and Blood Institute, Bethesda, MD 20892, USA.
Blood (Impact Factor: 10.45). 07/2007; 109(12):5234-7. DOI: 10.1182/blood-2006-12-063495
Source: PubMed


Perforin is a cytolytic protein expressed mainly in activated cytotoxic lymphocytes and natural killer cells. Inherited perforin mutations account for 20% to 40% of familial hemophagocytic lymphohistiocytosis, a fatal disease of early childhood characterized by the absence of functional perforin. Aplastic anemia, the paradigm of immune-mediated bone marrow failure syndromes, is characterized by hematopoietic stem cell destruction by activated T cells and Th1 cytokines. We examined whether mutations in the perforin gene occurred in acquired aplastic anemia. Three nonsynonymous PRF1 mutations among 5 unrelated patients were observed. Four of 5 patients with the mutations showed some hemophagocytosis in the bone marrow at diagnosis. Perforin protein levels in these patients were very low or absent, and perforin granules were completely absent. Natural killer (NK) cell cytotoxicity from these patients was significantly decreased. Our data suggest that PRF1 genetic alterations help explain the aberrant proliferation and activation of cytotoxic T cells and may represent genetic risk factors for bone marrow failure.

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    • "There are an increasing number of descriptions of atypical and late-onset cases of primary HLH. Patients may present with different clinical phenotypes, including aplastic anemia, autoimmune lymphoproliferative disease, recurrent fever, hypogammaglobulinemia and infection susceptibility (resembling common variable immunodeficiency), granulomatous lung or liver disease, or sterile encephalitis [16,17,56,57]. In one series up to 14% of adult patients presenting with HLH showed hypomorphic mutations in PRF1, MUNC13-4, and STXBP2, leading to less severe cytotoxicity defects that cause milder and atypical forms of HLH presenting beyond infancy [15]. "
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    ABSTRACT: Hemophagocytic lymphohistiocytosis (HLH) is a rare life-threatening disease of severe hyperinflammation caused by uncontrolled proliferation of activated lymphocytes and macrophages secreting high amounts of inflammatory cytokines. It is a frequent manifestation in patients with predisposing genetic defects, but can occur secondary to various infectious, malignant, and autoimmune triggers in patients without a known genetic predisposition. Clinical hallmarks are prolonged fever, cytopenias, hepatosplenomegaly, and neurological symptoms, but atypical variants presenting with signs of chronic immunodeficiency are increasingly recognized. Impaired secretion of perforin is a key feature in several genetic forms of the disease, but not required for disease pathogenesis. Despite progress in diagnostics and therapy, mortality of patients with severe HLH is still above 40%. Reference treatment is an etoposide-based protocol, but new approaches are currently explored. Key for a favorable prognosis is the rapid identification of an underlying genetic cause, which has been facilitated by recent immunological and genetic advances. In patients with predisposing genetic disease, hematopoietic stem cell transplantation is performed increasingly with reduced intensity conditioning regimes. Current research aims at a better understanding of disease pathogenesis and evaluation of more targeted approaches to therapy, including anti-cytokine antibodies and gene therapy.
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    • "Polymorphisms in the cytokine encoding genes increasing synthesis of TNF-α, IFN-γ, and IL-6 and causing apoptosis of marrow progenitors have also been described [20, 21]. Perforin gene mutations may cause abnormal proliferation and activation of cytotoxic T cells in AA [22]. T cell immune suppression is therapeutic in 75% of cases of AA [23]. "
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    • "The p.Ala91Val PRF1 variant has been previously reported in siblings with FHL and NHL [17,19], and in patients with Dianzani autoimmune lymphoproliferative disease [39] and aplastic anemia [40]. Here we identified this mutation in a patient with renal cancer with a family history of chronic myeloid leukemia (CML). "
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    ABSTRACT: ABSTRACT: Perforin gene (PRF1) mutations have been identified in some patients diagnosed with the familial form of hemophagocytic lymphohistiocytosis (HLH) and in patients with lymphoma. The aim of the present study was to determine whether patients with a familial aggregation of hematological malignancies harbor germline perforin gene mutations. For this purpose, 81 unrelated families from Tunisia and France with aggregated hematological malignancies were investigated. The variants detected in the PRF1 coding region amounted to 3.7% (3/81). Two of the three variants identified were previously described: the p.Ala91Val pathogenic mutation and the p.Asn252Ser polymorphism. A new p.Ala 211Val missense substitution was identified in two related Tunisian patients. In order to assess the pathogenicity of this new variation, bioinformatic tools were used to predict its effects on the perforin protein structure and at the mRNA level. The segregation of the mutant allele was studied in the family of interest and a control population was screened. The fact that this variant was not found to occur in 200 control chromosomes suggests that it may be pathogenic. However, overexpression of mutated PRF1 in rat basophilic leukemia cells did not affect the lytic function of perforin differently from the wild type protein.
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