Megakaryoblastic leukaemia and myelofibrosis complicating Fanconi anaemia

One Aeromonas salmonicida subsp. salmonicida isolate with a pAsa5 variant bearing antibiotic resistance and a pRAS3 variant making a link with a swine pathogen

The Gram-negative bacterium Aeromonas salmonicida subsp. salmonicida is an aquatic pathogen which causes furunculosis to salmonids, especially in fish farms. The emergence of strains of this bacterium exhibiting antibiotic resistance is increasing, limiting the effectiveness of antibiotherapy as a treatment against this worldwide disease. In the present study, we discovered an isolate of A. salmonicida subsp. salmonicida that harbors two novel plasmids variants carrying antibiotic resistance genes. The use of long-read sequencing (PacBio) allowed us to fully characterize those variants, named pAsa5-3432 and pRAS3-3432, which both differ from their classic counterpart through their content in mobile genetic elements. The plasmid pAsa5-3432 carries a new multidrug region composed of multiple mobile genetic elements, including a Class 1 integron similar to an integrated element of Salmonella enterica. With this new region, probably acquired through plasmid recombination, pAsa5-3432 is the first reported plasmid of this bacterium that bears both an essential virulence factor (the type three secretion system) and multiple antibiotic resistance genes. As for pRAS3-3432, compared to the classic pRAS3, it carries a new mobile element that has only been identified in Chlamydia suis. Hence, with the identification of those two novel plasmids harboring mobile genetic elements that are normally encountered in other bacterial species, the present study puts emphasis on the important impact of mobile genetic elements in the genomic plasticity of A. salmonicida subsp. salmonicida and suggests that this aquatic bacterium could be an important reservoir of antibiotic resistance genes that can be exchanged with other bacteria, including human and animal pathogens.

Secondary Bone Marrow Fibrosis in Children And Young Adults: An Institutional Experience

Secondary bone marrow fibrosis (BMF) is associated with many disease conditions in children, but its prevalence and characteristics have not been well elucidated. We present our experience with pediatric secondary BMF, in an attempt to characterize it in terms of underlying diagnoses, severity, and outcome. A retrospective chart review of patients diagnosed with secondary BMF by bone marrow aspirate and biopsy between January 1984 and April 2011 showed a total of 214 patients, the majority (67.1%) of whom had an underlying oncologic disease. At diagnosis, 87 patients (39.7%) had mild, 51 (23.3%) had moderate, and 33 (15.1%) had marked BMF; it was not quantified in 48 (21.9%) patients. An underlying oncologic disease was more frequently associated with marked fibrosis compared with hematologic and miscellaneous diagnoses. Follow-up posttreatment bone marrow aspirate assessments were available for 117 patients. The outcome ranges from worsening of fibrosis to complete resolution. A majority of these children (N=70/117, 60%) showed complete resolution of fibrosis. Of note, 27 patients had marked fibrosis at initial diagnosis and 16 (60%) of them showed complete resolution. These findings underscore the importance of appropriate treatment of the underlying disorder in reversing secondary BMF. Ours is the largest series of pediatric secondary BMF reported.

Secondary myelofibrosis in children

Myelofibrosis is a rare childhood myeloproliferative disorder. It has been reported as an associated complication of certain hematologic malignancies or as an isolated idiopathic process. We describe clinical course of 6 children diagnosed over 6 years. One child each responded well to steroid and treatment of the underlying condition. Three children died because of underlying conditions and 1 child was lost to follow up. A thorough search should be made for underlying disease when myelofibrosis is first diagnosed. Trephine biopsy though giving useful information, does not have a prognostic significance.

Cancer in Fanconi anemia, 1927-2001

BACKGROUND

Fanconi anemia (FA) is an autosomal recessive disease associated with an abnormal response to DNA damage. Although FA is well known for the association of aplastic anemia and characteristic birth defects, leukemia and solid tumors also occur at a high rate in this group of patients. A review of all reported cases is informative with regard to the specific types of cancer, the ages at which they occur, and the cumulative probability of their development.

METHODS

Medline and bibliographies of publications were searched for articles containing "Fanconi's anemia" or "aplastic anemia" and all cases of FA from 1927 through 2001 were included in the database. Cancer cases were identified within these reports. Descriptive statistical analyses were performed using Stata7 software.

RESULTS

One thousand three hundred cases of FA were identified. Nine percent had leukemia (primarily acute myeloid leukemia), 7% had myelodysplastic syndrome, 5% had solid tumors, and 3% had liver tumors. Patients with cancer were older than the cancer-free patients at the time of diagnosis of FA. The median age for cancer (including leukemia) was 16, compared with 68 in the general population. The most frequent solid tumors were aerodigestive and gynecological carcinomas. In approximately 25% of patients with cancer, the malignancy preceded the diagnosis of FA.

CONCLUSIONS

If the competing risks of aplastic anemia and leukemia could be removed, the estimated cumulative probability of development of a solid tumor in FA patients is 76% by the age of 45 years. Carcinogenic pathways and cancer prevention, surveillance, and treatment can be studied to advantage in this genetic model of human cancer.

Fanconi's anemia and malignancies

Patients with Fanconi's anemia (FA) are at a high risk for development of malignancies. It is well-known that leukemia occurs in approximately 10% of cases, with increasing risk with age. Less commonly recognized is the risk for myelodysplastic syndromes (approximately 5%); the relationship between myelodysplasia and evolution to leukemia remains speculative. What also needs to be emphasized is that older patients have an ever-increasing risk for development of solid tumors, with at least 5% reported to have liver tumors (male:female ratio, 2:1) and an equal number of other cancers (female:male ratio, 3:1, even after exclusion of gynecologic malignancies). Hematologists have tended to focus on aplastic anemia and leukemia. As FA patients live longer, more of the other malignancies will occur, perhaps related to cord blood or bone marrow transplant, or treatment with cytokines. This review identifies the types of tumors for which patients with Fanconi's anemia are at risk.

Acute megakaryoblastic leukemia in children and adolescents: a retrospective analysis of 24 cases

In order to characterize the clinical, cytogenetic, and outcome features of childhood acute megakaryoblastic leukemia (AMKL), we reviewed 24 cases; 14 were identified among 150 consecutive newly diagnosed acute myelogenous leukemia (AML) patients at St. Jude Children's Research Hospital, and 10 were cases referred to the National Institute of Cancer in Rio de Janeiro, Brazil. There were 5 Down syndrome patients and one patient with chronic myeloid leukemia (Ph+) in blastic crisis. Twelve patients had significant hepatosplenomegaly. Leukemic cell morphology and cytochemistry were consistent with the M7 classification in 17 cases, and all cases tested expressed megakaryocytic surface antigens. AMKL patients were significantly younger than other AML patients (P = 0.0001) and had poorer responses to therapy (P = 0.03, univariate analysis only). Ten of 24 failed induction, and only 5 are disease-free at 6 months to 4.5+ years. We conclude that AMKL usually affects young children, frequently producing marked organomegaly. It comprises approximately 10% of pediatric AML cases, and responds poorly to intensive AML therapies.

Fanconi's anaemia and post-cricoid carcinoma

A case of post-cricoid carcinoma, occurring in a patient with Fanconi's anaemia is presented. The case illustrates the rare association of the two diseases. The problems with the management of such a case are discussed.

Leukemia and preleukemia in Fanconi anemia patients. A review of the literature and report of the International Fanconi Anemia Registry

Fanconi anemia (FA) is an autosomal recessive disorder characterized clinically by a progressive pancytopenia, diverse congenital abnormalities, and increased predisposition to malignancy. Although a variable phenotype makes accurate diagnosis on the basis of clinical manifestations difficult in some patients, the unique sensitivity of FA cells to the clastogenic effect of DNA cross-linking agents such as diepoxybutane (DEB) can be used to facilitate the diagnosis. We review all cases of FA reported to have leukemia, preleukemia, or a bone marrow (BM) clonal chromosomal abnormality and include for the first time an analysis of these conditions observed in patients in the International Fanconi Anemia Registry (IFAR). The incidence of acute myelogenous leukemia (AML) in FA patients is more than 15,000 times that observed in children in the general population. Cytogenetic studies of FA-associated leukemias disclose a high frequency of monosomy 7 and duplications involving 1q. There were no occurrences of t(8;21), t(15;17), or abnormalities of 11q, which are associated with M2, M3, and M5 leukemias, respectively, but not with preleukemia. Development of leukemia in FA patients was associated with an exceedingly poor prognosis, with a mean age of death of 15 years. We suggest that all FA patients may be considered preleukemic and that this disorder presents a model for study of the etiology of AML.

Acute megakaryocytic leukemia (M7) in children

We analyzed the clinical and laboratory features of eight children (median age, 20 months; range, 13 months to 11 years) with acute megakaryocytic leukemia (M7) and compared the findings with those reported in the literature. The diagnosis was supported by ultrastructural examination for platelet peroxidase or immunophenotyping for glycoprotein IIb/IIIa or the von Willebrand factor protein. Two patients had Down's syndrome. Initial findings included anemia (in all patients), thrombocytopenia (in six), myelofibrosis (in three), lytic bone lesions (in two), and pronounced leukocytosis (in one). Stem cell culture studies of peripheral blood specimens revealed an aberrant phenotype of the megakaryocytes in one patient and reversal to a normal pattern after successful therapy. Remission was achieved in seven of the eight patients after aggressive chemotherapy, and four patients remained in remission 27 to 57 months after diagnosis. Three of these four patients underwent allogeneic bone marrow transplantation. M7 leukemia is not infrequent in children younger than 3 years of age, especially in those with Down's syndrome. The availability of monoclonal antibodies specific to restricted antigens of the megakaryocytic lineage has made the diagnosis of M7 leukemia both possible and practical.

Dicentric chromosome in the bone marrow of a child with megakaryoblastic leukaemia and Down's syndrome

A two year old girl with Down's syndrome (constitutional karyotype: 47 + 21), presenting with pancytopenia, developed acute megakaryoblastic leukaemia (AMKL). Her bone marrow contained an abnormal clone with a novel dicentric chromosome derived from chromosomes 5 and 7 (karyotype 46, XX, -5, -7, +dic (5;7) (p 13; p 11.2), +21. This case provides further evidence for a connection between chromosome 21 and this unusual form of childhood leukaemia, and raises questions about the loss of short arm material from chromosomes 5 and 7 compared with the more usual monosomy or long arm loss.

Human megakaryocytic progenitor cells

Megakaryocytopoiesis represents one of several differentiation pathways that hematopoietic stem cells may enter. Cells representing intermediate stages of differentiation between pluripotent stem cells and maturing megakaryocytes are called megakaryocytic progenitor cells. They are identified in human bone marrow and peripheral blood by their ability to proliferate in culture (colony forming unit-megakaryocyte, CFU-M); at some point they lose the capacity for cell division and acquire the ability for endoreduplication of DNA, a phenomenon that is unique to the megakaryocyte lineage. This review summarizes current understanding of the biology of human megakaryocytic progenitor cells, including characterization of their proliferation potentials, their antigenic determinants, and the mechanisms that govern their proliferation and maturation. Finally the involvement of CFU-M in various disorders of thrombopoiesis is discussed.