Juvenile myelomonocytic leukemia

Glomus tumors in neurofibromatosis type 1: genetic, functional, and clinical evidence of a novel association

Neurofibromatosis type 1 (NF1) is a common disorder that arises secondary to mutations in the tumor suppressor gene NF1. Glomus tumors are small, benign but painful tumors that originate from the glomus body, a thermoregulatory shunt concentrated in the fingers and toes. We report 11 individuals with NF1 who harbored 20 glomus tumors of the fingers and 1 in the toe; 5 individuals had multiple glomus tumors. We hypothesized that biallelic inactivation of NF1 underlies the pathogenesis of these tumors. In 12 NF1-associated glomus tumors, we used cell culture and laser capture microdissection to isolate DNA. We also analyzed two sporadic (not NF1-associated) glomus tumors. Genetic analysis showed germ line and somatic NF1 mutations in seven tumors. RAS mitogen-activated protein kinase hyperactivation was observed in cultured NF1(-/-) glomus cells, reflecting a lack of inhibition of the pathway by functional neurofibromin, the protein product of NF1. No abnormalities in NF1 or RAS mitogen-activated protein kinase activation were found in sporadic glomus tumors. By comparative genomic hybridization, we observed amplification of the 3'-end of CRTAC1 and a deletion of the 5'-end of WASF1 in two NF1-associated glomus tumors. For the first time, we show that loss of neurofibromin function is crucial in the pathogenesis of glomus tumors in NF1. Glomus tumors of the fingers or toes should be considered as part of the tumor spectrum of NF1.

Development of an allele-specific minimal residual disease assay for patients with juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia is an aggressive and frequently lethal myeloproliferative disorder of childhood. Somatic mutations in NRAS, KRAS, or PTPN11 occur in 60% of cases. Monitoring disease status is difficult because of the lack of characteristic leukemic blasts at diagnosis. We designed a fluorescently based, allele-specific polymerase chain reaction assay called TaqMAMA to detect the most common RAS or PTPN11 mutations. We analyzed peripheral blood and/or bone marrow of 25 patients for levels of mutant alleles over time. Analysis of pre-hematopoietic stem-cell transplantation, samples revealed a broad distribution of the quantity of the mutant alleles. After hematopoietic stem-cell transplantation, the level of the mutant allele rose rapidly in patients who relapsed and correlated well with falling donor chimerism. Simultaneously analyzed peripheral blood and bone marrow samples demonstrate that blood can be monitored for residual disease. Importantly, these assays provide a sensitive strategy to evaluate molecular responses to new therapeutic strategies.

Chilblain-like leukemia cutis

We present a 6-year-old girl with an 8-month history of fluctuating chilblain-like lesions on the toes. A full blood count showed slight thrombocytopenia and monocytosis. A skin biopsy specimen showed a dense perivascular and superficial dermal cellular infiltrate which was CD3(-), CD43(+), and lysosyme + on immunocytochemistry, suggesting a monocytic origin. Juvenile myelomonocytic leukemia was diagnosed after a bone marrow biopsy and spontaneous marrow colony growth in culture.

A case of juvenile myelomonocytic leukemia with concomitant cytomegalovirus infection

Infantile cytomegalovirus (CMV)-associated disease and juvenile myelomonocytic leukemia (JMML) frequently present with similar clinical features, and thus the differential diagnosis is often difficult. An early and definite diagnosis of these disorders is required because their therapeutic approaches are very different. The authors describe a 2-month-old Japanese girl with JMML and CMV infection. The CMV antigen was detected by immunologic staining of leukocytes using the peroxidase-labeled monoclonal antibody HRP-C7. To assess clonality, the X-chromosome inactivation pattern was evaluated using polymerase chain reaction analysis of the human androgen receptor gene with or without predigestion of chromosomal DNA with HhaI or HpaII. The patient showed evidence of monoclonal origin of mononuclear cells at diagnosis. Although CMV infection mimicking JMML has previously been reported in two patients, to the authors' knowledge this is the first report describing a firm and definitive diagnosis of JMML based on the study of X-chromosome inactivation patterns.