Agnogenic myeloid metaplasia in childhood: a report of two cases and efficiency of intravenous high dose methylprednisolone treatment

Childhood Primary Myelofibrosis Presented with Headache, Splenomegaly, and Severe Thrombocytosis: A Case Report

Primary myelofibrosis (PMF) is a clonal disorder of a multipotent hematopoietic progenitor cell that occurs predominantly in the elderly age group. We report here an 11-year-old girl who presented with headache, fever, and splenomegaly. Full blood cell count revealed severe thrombocytosis. Laboratory and radiology examinations excluded the diagnosis of essential/reactive thrombocytosis. Bone marrow biopsy showed megakaryocytic hyperplasia, reticulin and collagen fibrosis, and erythroid and myeloid hypoplasia, findings compatible to PMF. The patient was put symptomatically on hydroxyurea and hydration due to thrombocytosis and platelet number decreased. Hematopoietic stem cell transplantation was scheduled to avoid delaying definitive therapy and secondary complications such as infections and transfusion dependency. To the best of our knowledge, this is the first reported case of PMF in childhood in Greece.

Myeloproliferative Neoplasms in Children

Myeloproliferative neoplasms (MPN) are a group of clonal hematopoietic stem cell disorders characterized by aberrant proliferation of one or more myeloid lineages often with increased immature cells in the peripheral blood. The three classical BCR-ABL-negative MPNs are: 1) polycythemia vera (PV), 2) essential thrombocythemia (ET), and 3) primary myelofibrosis (PMF), which are typically disorders of older adults and are exceedingly rare in children. The diagnostic criteria for MPNs remain largely defined by clinical, laboratory and histopathology assessments in adults, but they have been applied to the pediatric population. The discovery of the JAK2 V617F mutation, and more recently, MPL and CALR mutations, are major landmarks in the understanding of MPNs. Nevertheless, they rarely occur in children, posing a significant diagnostic challenge given the lack of an objective, clonal marker. Therefore, in pediatric patients, the diagnosis must rely heavily on clinical and laboratory factors, and exclusion of secondary disorders to make an accurate diagnosis of MPN. This review focuses on the clinical presentation, diagnostic work up, differential diagnosis, treatment and prognosis of the classical BCR-ABL-negative MPNs (PV, ET and PMF) in children and highlights key differences to the adult diseases. Particular attention will be given to pediatric PMF, as it is the only disorder of this group that is observed in infants and young children, and in many ways appears to be a unique entity compared to adult PMF.

A basic classification and a comprehensive examination of pediatric myeloproliferative syndromes

Myeloproliferative syndromes (MPSs) are clonal stem cell disorders resulting in excessive proliferation of one or more cell lineages. Since MPSs in children occur much less commonly than adults, one can argue that the biology and the categories of the various pediatric MPSs seem to be different from adults. Furthermore, confusion exists between pediatric MPS and other overlapping conditions, such as myelodysplastic syndrome. The authors' objectives were to develop a classification system with a list of disorders relevant to children and to characterize pediatric cases of MPS that were devised according to this classification. Based on the predominant proliferating cell lineage, the authors established a classification system for childhood MPS. Primary MPS was classified into granulocytic proliferation--chronic myelogenous leukemia (CML); monocytic--juvenile myelomonocytic leukemia (JMML); megakaryocytic--essential thrombocythemia (ET), familial thrombocytosis, transient myeloproliferative disorder of Down syndrome (TMD); erythrocytic--polycythemia vera, familial erythrocytosis; fibroblastic--idiopathic myelofibrosis (IMF); eosinophilic--idiopathic hypereosinophilic syndrome (IHES); and mast cells--mastocytosis. Secondary MPS was classified as non-clonal proliferation (eg, infections, drugs, toxins, autoimmune, non-hematologic neoplasm, and trauma), and these were excluded from the study. Next, the classification system was applied to the patient population at the authors' institution. One hundred two cases with primary MPS were identified between 1970 and 2001. Patients were evaluated for clinical manifestations, blood and bone marrow parameters, cytogenetics, and survival following different treatment modalities. Significant proportions of cases of childhood MPS (60%) were unique to the pediatric population and not seen in adults. The most common disorders were JMML (n = 31), TMD of Down syndrome (n = 30), and CML (n = 30); the other disorders were rare: four cases of ET, two of IMF, two of IHES, two of mastocytosis, and one primary erythrocytosis. In contrast to adults, MPS in children is more frequently treated with hematopoietic stem cell transplantation (HSCT), the only available curative option for most of these diseases. HSCT was particularly successful in the more recent cases due to more advanced techniques for HSCT. The authors found that all the cases could be easily classified. MPS in children is different from adult-type MPS in terms of biology, categories, classification, and prognosis.

Long-term survival of infants with idiopathic myelofibrosis

Idiopathic myelofibrosis can develop in children as well as adults. However, the disease appears to be much more aggressive in adults, being characterized by poor survival rates and a high frequency of malignant transformation. Here, we describe three cases of idiopathic myelofibrosis in infants, two of whom were followed for 16 and 22 years after diagnosis. Neither of these patients required more than minimal supportive care, and both have had spontaneous erythropoietic recovery as early as 2-3 years after diagnosis. There have been no indications of malignant transformation or clinical deterioration. Thus, idiopathic myelofibrosis may have a different pathogenesis and clinical course in infants from adults, requiring a more conservative approach to management.

Successful treatment of essential thrombocythemia evolving into agnogenic myeloid metaplasia with interferon-alpha

PURPOSE

Essential thrombocythemia and agnogenic myeloid metaplasia as one form of idiopathic myelofibrosis are myeloproliferative disorders and are quite rare in children. A patient with essential thrombocythemia that transformed to "adult-type" agnogenic myeloid metaplasia is described.

PATIENTS AND METHODS

A routine examination of an 8-year-old girl with bronchial asthma showed thrombocytosis. Essential thrombocythemia was diagnosed 2 years later. During a 3-year follow-up without treatment, transition of the essential thrombocythemia to agnogenic myeloid metaplasia was noticed. The patient had an excellent response to interferon (IFN)-alpha therapy.

CONCLUSION

This case is unique because of the availability of premorbid hematologic data and the natural progression of essential thrombocythemia to agnogenic myeloid metaplasia. Whether IFN-alpha therapy can prevent the progression of idiopathic myelofibrosis to leukemia has not yet been determined.