Pathophysiology of aplastic anaemia

Idiopathic Aplastic Anemia in Children and Adults: Diagnosis, Treatments, and Management - A Review

Aplastic Anemia (AA) is also known as idiopathic aplastic anemia (IAA) and the production of new blood cells ceases in AA, which leads to an abnormal hematological syndrome such as pancytopenia and suppression of hypo-cellular bone marrow. The pathophysiology of AA in most cases is immune-mediated and is stimulated by type 1 cytotoxic T cells. Reliable early diagnostic tests of IAA are not yet available, therefore most of the cases are identified in advanced stages. Recently, abnormal immune response and hematopoietic cell deficiencies are defined genetically, such as in target cells of telomere repair gene mutations and by the dysregulation of T-cell activation pathways. Importantly, anti-thymocyte globulins and cyclosporine-associated immunosuppression are successful treatments for restoring blood cell production in most of the cases, however, clonal hematologic diseases remain challenging. In the current review, we have discussed the common practices in the treatment, pathophysiology, diagnosis, and management of AA.

Periodontal Treatment in Severe Aplastic Anemia

BACKGROUND

Aplastic anemia (AA) is a rare hematologic disease characterized by hypo-cellular bone marrow. The clinical features include fatigue, increased bruising, and gingival bleeding caused by anemia, leukopenia, and thrombocytopenia. A patient with AA is at high risk for infection because of leukopenia. The risk of systemic infection is especially high in AA patients with severe local infections, including periodontitis. Accordingly, periodontal treatment should include antibiotic prophylaxis to reduce the risk of systemic infection. However, treatment of periodontitis in the AA patient is significantly complicated by the bleeding disorder. We present a case report of the successful periodontal treatment of an AA patient with spontaneous gingival bleeding.

METHODS

The patient was closely monitored for platelet and neutrophil counts before every treatment. The patient's platelet count was always under 10,000/microl. Therefore, it was necessary to increase platelet counts to over 25,000/microl by transfusion, after which subgingival scaling with anesthesia was performed. When the neutrophil count was less than 2,000/microl, local minocycline chemotherapy was applied to the pockets. Periodontal infection was monitored by detection of bacterial DNA and measurement of serum immunoglobulin (Ig) G titer against periodontal bacteria.

RESULTS

Following the physical and chemical treatment, the gingival appearance improved dramatically and the spontaneous gingival bleeding disappeared. Moreover, the IgG titer against periodontal bacteria decreased to normal range and specific periodontal pathogens were no longer detectable in the tested pockets.

CONCLUSION

We believe that the treatment strategy in the present report provides new sight into treatment planning for severely medically compromised patients.

Lack of known hepatitis virus in hepatitis-associated aplastic anemia and outcome after bone marrow transplantation

Viral infection has been shown to induce aplastic anemia, unidentified types of hepatitis being the most common cause for aplastic anemia-associated viral hepatitis. The survival rate for this group of patients after bone marrow transplantation with stem cells from an HLA-matched sibling is not well known. The aim of this study was to determine the prevalence of hepatitis G virus (HGV) and transfusion transmitted virus (TTV) infection in non-A, non-B, non-C hepatitis associated-aplastic anemia (HAAA) patients, and to define the role of bone marrow transplantation (BMT) as a therapeutic modality for this disease. Sixty-eight patients (43 males and 25 females) with aplastic anemia, underwent allogeneic BMT at the Hadassah University Hospital between 1981 and 1997. Onset of hepatitis was defined as jaundice and elevated alanine aminotransaminase (ALT) levels. Onset of aplastic anemia was defined as the first date on which varying degrees of pancytopenia occurred: hemoglobin level below 10 g/dl, WBC below 2 x 10(9)/l and low platelet count 10 x 10(10)/l. Serial serum samples from HAAA patients were assayed for virological and/or serological markers of hepatitis A, B, C, D, E, G viruses, TTV and parvovirus B19. Seventeen of the 68 patients with aplastic anemia (25%) suffered from hepatitis, 12 males and five females, ages 5 to 36 years. The mean interval between onset of hepatitis and first indication of aplastic anemia was 62 days (range 14-225 days). The development of aplastic anemia was unrelated to age, sex or severity of hepatitis. Ten of the 17 patients (59%) achieved complete ALT recovery prior to the diagnosis of aplastic anemia. Serum samples were available for 15 patients; none had evidence of acute or active hepatitis A, B, C, D, E, G and TTV virus infection at the time of diagnosis. Parvovirus B19 DNA sequences were not detectable in 10 of 12 tested cases; two positive results were detected in serum samples obtained after blood transfusion, making the analysis of these positive results difficult. All 17 patients underwent BMT. The mean post-BMT follow-up period was 38 months (range 1 day-123 months), five patients (30%) died 1 to 160 days post BMT, and 12 (70%) are alive 31 to 123 months after BMT. Relapsing hepatitis was not observed in any of the patients. In conclusion, HAAA is a disease of the young and the etiologic agent associated with HAAA remains unknown. HGV, TTV and parvovirus B19 sequences were not detected in any of the HAAA cases. The survival rate after BMT with stem cells from an HLA-matched sibling is similar to that for patients with non-hepatitis-associated aplastic anemia.

Long-term follow-up of aplastic anaemia

Of 61 patients with aplastic anaemia (AA) diagnosed in our hospitals, 37 survived more than 2 years; actuarial survival of this latter group was 58%, with a median follow-up of living patients of 10.2 years. Laboratory and clinical data pertaining to these long-term survivors was scrutinized to determine the incidence of clonal disorders, which was identified in 43%. Morphological evidence of the myelodysplastic syndrome (MDS) was found in 13 (35%), including four cases of RAEB; four (11%) developed PNH. Of 23 patients studied, four showed karyotypic abnormalities, but these did not always coincide with morphological features of MDS. Although four patients now have completely normal blood and marrow morphology, and another had normal blood and marrow morphology at the time of death due to unrelated disease, the study confirms the high incidence of cytopenia and morphological abnormality, sufficient to justify a diagnosis of MDS, in patients with a history of AA. No definite survival plateau was identified. However, the natural history of MDS secondary to AA seems to be different to that of MDS arising de novo; the clinical course is relatively indolent, possibly implying a different biology.

Severe aplastic anemia (SAA): response to cyclosporin A (CyA) in vivo and in vitro

The aim of the present study was to test the effect of cyclosporin A (CyA) in vitro on CFU-GM growth from patients with severe aplastic anemia (SAA). For this purpose, bone marrow (BM) cells from 9 SAA patients and 5 healthy individuals were incubated with or without CyA and then cultured for CFU-GM growth in the presence of exogenous recombinant human GM-CSF (30 ng/ml). SAA patients were tested before or after treatment with CyA, or after treatment with antilymphocyte globulin (ALG). In 3 patients responding to CyA, the addition of CyA in vitro enhanced colony growth from 13 +/- 10 to 40 +/- 20/10(5) BM cells (p = 0.01) - the median increment of colony formation was 2.4-fold. In 5 ALG responders, CyA produced no increment of CFU-GM growth (from 14 +/- 26 to 15 +/- 16/10(5) BM cells, p = 0.1). CyA did not enhance significantly CFU-GM growth in normal controls (from 57 +/- 45 to 58 +/- 81/10(5) BM cells, p = 0.9). In conclusion, it would appear that some patients with SAA can respond to CyA in vivo and in vitro, and ALG responders are not necessarily among these. This is in keeping with different mechanisms of action of CyA and ALG and possibly with the existence of distinct pathogenetic pathways in SAA.

Aplastic anemia: current concepts and dental management

Aplastic anemia (AA) is a rare blood dyscrasia in which the peripheral blood cells are decreased because of bone marrow failure. The clinical course reflects the severity of pancytopenia and is unpredictable for the individual. Hemorrhage and infection remain the major threats to these patients. Recent advances in transfusion medicine, infection management, bone marrow transplantation, and immunosuppressive therapy have improved survival of patients with AA. Oral manifestations of AA are common and may have serious sequelae. Two cases of acute periodontal infection associated with AA are presented. Dental management guidelines are presented in the context of interdisciplinary care.