Human herpesvirus 6 infection and transient acquired myelodysplasia in children

Acquired and hereditary bone marrow failure: A mitochondrial perspective

The disorders known as bone marrow failure syndromes (BMFS) are life-threatening disorders characterized by absence of one or more hematopoietic lineages in the peripheral blood. Myelodysplastic syndromes (MDS) are now considered BMF disorders with associated cellular dysplasia. BMFs and MDS are caused by decreased fitness of hematopoietic stem cells (HSC) and poor hematopoiesis. BMF and MDS can occur de novo or secondary to hematopoietic stress, including following bone marrow transplantation or myeloablative therapy. De novo BMF and MDS are usually associated with specific genetic mutations. Genes that are commonly mutated in BMF/MDS are in DNA repair pathways, epigenetic regulators, heme synthesis. Despite known and common gene mutations, BMF and MDS are very heterogenous in nature and non-genetic factors contribute to disease phenotype. Inflammation is commonly found in BMF and MDS, and contribute to ineffective hematopoiesis. Another common feature of BMF and MDS, albeit less known, is abnormal mitochondrial functions. Mitochondria are the power house of the cells. Beyond energy producing machinery, mitochondrial communicate with the rest of the cells via triggering stress signaling pathways and by releasing numerous metabolite intermediates. As a result, mitochondria play significant roles in chromatin regulation and innate immune signaling pathways. The main goal of this review is to investigate BMF processes, with a focus mitochondria-mediated signaling in acquired and inherited BMF.

How I investigate dysgranulopoiesis

Dysgranulopoiesis is a condition in which granulocytic production is defective and is most often described in neoplastic conditions. However, it can also be frequently seen in non-neoplastic conditions. Early suspicion and detection of these non-neoplastic causes may prevent further invasive and expensive interventions. In this review, we take a look at the various causes of dysgranulopoiesis with an emphasis on non-neoplastic etiologies, followed by a detailed outline of the laboratory approach for determining its many causes.

The epidemiology, clinical course and outcome of febrile cytopenia in children

AIM

Transient infectious neutropenia of mild-to-moderate severity is common and resolves spontaneously within weeks. This was the first prospective study of the whole spectrum of febrile cytopenia in noncancer patients followed-up for 2 years. It aimed to assess its aetiology, duration and outcome.

METHODS

We evaluated 116 children with febrile cytopenia aged 4 ± 3.8 years, admitted to a paediatric ward over 2 years, using inflammatory markers, cultures and serological tests.

RESULTS

An infectious agent was identified in 74 (63.8%) cases: 44.8% viral, 11.2% bacterial and 7.8% parasitic. One cell line was affected in 26.7% of patients and ≥2 cell lines in 73.3%. Cytopenia was transient in 82.75% of cases and chronic in 17.24%. The transient cytopenia subgroups - exhibited differences in severity (mild in bacterial cases and moderate in viral and parasitic cases, p = 0.018) and the number of affected cell lines, (predominantly two in viral and bacterial cases and pancytopenia in parasitic cases, p = 0.001). Chronic patients had severe cytopenia (p = 0.004) with ≥2 cell lines affected, while transient patients had mild-to-moderate cytopenia, with 1-3 cell lines affected.

CONCLUSION

Childhood febrile cytopenia is usually transient, of mild-to-moderate severity, and resolves spontaneously, but patients with severe cytopenia affecting ≥2 cell lines need further evaluation and follow-up.

Update on Myelodysplastic Syndromes Classification and Prognosis

Myelodysplastic syndromes (MDS) are a collection of cytogenetically heterogeneous clonal bone marrow (BM) failure disorders derived from aberrant hematopoietic stem cells in the setting of an aberrant hematopoietic stem cell niche. Patients suffer from variably progressive and symptomatic bone marrow failure with a risk of leukemic transformation. Diagnosis of MDS has long been based on morphologic assessment and blast percentage as in the original French-American-British classification. The recently developed Revised International Prognostic Scoring System provides improved prognostication using more refined cytogenetic, marrow blast, and cytopenia parameters. With the advent of deep sequencing technologies, dozens of molecular abnormalities have been identified in MDS.

Infections in myelodysplastic syndromes

Myelodysplastic syndromes are associated with a risk of severe infections. While neutropenia is likely to be the main predisposing factor, several other immune defects have been reported, including impaired neutrophil function, B-, T- and NK-cell defects and the possible consequences of iron overload due to red blood cell transfusions. The advanced age of most patients, their frequent comorbidities, and the fact that drugs such as hypomethylating agents and lenalidomide, which are effective in myelodysplastic syndromes but can transiently worsen neutropenia, may increase the risk of infection and their severity in this context. The majority of infections in myelodysplastic syndromes are bacterial, while the incidence of fungal infections is not well known and viral infections seem to be rare. No prophylactic measures against infections have demonstrated efficacy in myelodysplastic syndromes. However, pending more data, we propose here some recommendations for the management of patients with myelodysplastic syndromes. In the future, an important contribution can be made by prospective trials testing the efficacy of prophylactic and therapeutic approaches to infection in these patients, especially in the context of the new drugs available for myelodysplastic syndromes.

HHV-6 infection of tonsils and adenoids in children with hypertrophy and upper airway recurrent infections

OBJECTIVE

Human herpes virus 6 (HHV-6), the agent of a self-limiting exanthematic disease in childhood, persists in a silent state in the secondary lymphoid organs and the reactivation is characterized by HHV-6-induced inflammatory cytokines. This study investigates the possible etiological role of HHV-6 in children affected by tonsil and adenoid hypertrophy.

METHODS

55 tonsils, 80 adenoids fresh tissues and 74 blood samples were collected from 80 children (mean age 4.8 years, 43.5% female) undergoing elective tonsillectomy and/or adenoidectomy for tissue hypertrophy. Moreover, patients with <5 years old documented upper airway recurrent infections not related to relapsing of acute tonsillitis. Specific IgG antibodies and virus detection (by PCR, variant A/B enzymatic genotyping and real-time PCR) were performed.

RESULTS

In our series, HHV-6 seroprevalence was tested at 50%. HHV-6 variant B was the unique strain finding in 25% of adenoids, in 12.7% of tonsils and in 4% of peripheral blood mononuclear cells (PBMCs). HHV-6-B was prevalent in tonsils of children affected by upper airway infections (17.8% vs 7.4%) while the adenoids represented the more frequent reservoir (30.7% vs 19.5%) in patients with hypertrophy. HHV-6 viral load was low, ranging from 80 to 600 copies/10(6) cells suggesting a latent/persistent phase of infection.

CONCLUSION

These results reinforce the role of the secondary lymphoid organs as an important reservoir for HHV-6B. Nevertheless, infection of lymphoid cells, sustained by a low level of replication, could be sufficient to increase the local injury through an autologous mechanism of inflammation.

Transient myelodysplastic syndrome in X-linked agammaglobulinemia with a novel Btk mutation

X-linked agammaglobulinemia (XLA) is a rare disorder in which recurrent infections occur due to low serum globulins and circulating B lymphocytes caused by a mutation in the Bruton tyrosine kinase (Btk) gene. While myelodysplastic syndrome (MDS) associated with low B lymphocyte counts has been described, clonal cytogenetic abnormalities in confirmed cases of XLA have never been reported. We describe a case of XLA with a novel Btk mutation who also had a persistent clonal population in the bone marrow with abnormal cytogenetics in multiple chromosomes that resolved 1(1/2) years after treatment with IVIG, mimicking a picture of transient MDS.

Bone marrow findings in juvenile idiopathic arthritis

The diagnosis of juvenile idiopathic arthritis (JIA) is an exclusion one due to heterogeneous clinical presentation and lack of specific laboratory tests. The authors investigated bone marrow of 25 untreated children with JIA at the onset of the disease. Bone marrow smears were evaluated for cell populations as well as myelodysplastic features and compared to two control groups. The characteristic of bone marrow in JIA was myeloid hyperplasia and elevated plasmocyte count. There was no difference between JIA patients and control groups in terms of myelodysplastic features. These findings can be helpful in explaining hematological alterations in JIA.

Myelodysplastic syndromes in children: a critical review of issues in the diagnosis and classification of 887 cases from 13 published series

CONTEXT

Pediatric myelodysplastic syndromes (MDSs) are uncommon disorders, which may be difficult to diagnose, particularly in the absence of increased blasts. Pediatric MDSs have several unique features including their association with inherited/constitutional disorders in approximately one third of patients. The classification of pediatric MDSs has undergone significant evolution in the past 20 years.

OBJECTIVE

To critically review existing classifications of pediatric MDSs and to evaluate their applicability on previously published large series.

DATA SOURCES

Previously published pediatric MDS series containing more than 10 patients from the English literature between 1982 and 2005.

CONCLUSIONS

Data were available on 887 patients from 13 published series. Most cases (68.7%) were idiopathic/de novo, 23.9% were associated with constitutional/inherited disorder, and 7.4% were therapy related. Approximately 10% of cases could not be classified by the French-American-British classification. Eighty-seven percent of unclassified cases were appropriately classified using the World Health Organization classification (2001), whereas 96% of them were classified with the modified World Health Organization classification for pediatric MDSs (2003). The impact of cytogenetics and constitutional/inherited disorders on the biology and outcome of the disease needs to be studied further.

Donor-Type Myelodysplastic Syndrome with t(2;3) and Monosomy 7 after Allogeneic Peripheral Blood Stem Cell Transplantation and Liver Transplantation in a Patient with Severe-Type Aplastie Anemia

Secondary clonal hemaloiogical disease in donor cells has rarely been reported as a complication of allogeneic stem cell transplantation in hematological disease. We report a case of myelodysplastic syndrome that showed cytogenetic abnormalities of t(2;3) and monosomy 7, which developed 2 years after peripheral blood stem cell transplantation for aplastic anemia and 1 year after liver transplantation for drug-induced hepatic failure. This secondary malignancy of donor origin is most frequently seen in patients with leukemia. We suspect that the chromosomal abnormalities are related to hepatitis-associated aplastic anemia, administration of granulocyte colony-stimulating factor and erythropoietin for posttransplantion pancytopenia, and repeated infections after liver transplantation.