Bacille Calmette-Guérin (BCG) is a live-attenuated vaccine routinely administered to newborns to prevent severe forms of tuberculosis (TB) in TB-endemic countries. Disseminated BCG vaccine disease is a classic feature of children with human immunodeficiency virus (HIV) or primary immunodeficiency disorders (PIDs) and is associated with high mortality. We report a case of a 6-month-old infant with disseminated BCG disease and hemophagocytic lymphohistiocytosis mimicking juvenile myelomonocytic leukemia with no demonstrable features of HIV or PID even after extensive laboratory work-up and succumbed to progressive disease. Disseminated BCG disease is a rare and potentially fatal complication of BCG vaccine, and prompt immunological evaluation complemented by initiation of 4-drug antitubercular therapy and definitive treatment with antiretroviral therapy or hematopoietic stem cell transplant is warranted.

Takayasu arteritis (TA) is a large-vessel vasculitis that rarely presents in infancy. Casitas B-lineage lymphoma (CBL) syndrome is a rare genetic disorder due to heterozygous CBL gene germline pathogenic variants that is characterized by a predisposition to develop juvenile myelomonocytic leukemia (JMML). Vasculitis, including TA, has been reported in several patients. Herein, we describe a patient with CBL syndrome, JMML, and TA, developing long-term remission of this vasculitis after allogeneic hematopoietic stem cell transplant (HSCT), and perform a literature review of CBL syndrome with vasculitis or vasculopathy. We report a female patient with growth delay, developmental issues, and congenital heart disease who was admitted at 14 months of age with massive splenomegaly, lymphadenopathy, fever, and hypertension. Body imaging studies revealed arterial stenosis and wall inflammation of the aorta and multiple thoracic and abdominal branches. Whole exome sequencing revealed a pathogenic variant in CBL with loss of heterozygosity in blood cells, diagnosing CBL syndrome, complicated by JMML and TA. Allogeneic HSCT induced remission of JMML and TA, permitting discontinuation of immunosuppression after 12 months. Six years later, her TA is in complete remission off therapy. A literature review identified 18 additional cases of CBL syndrome with vasculitis or vasculopathy. The pathogenesis of vasculitis in CBL syndrome appears to involve dysregulated T cell function and possibly increased angiogenesis. This case advances the understanding of vascular involvement in CBL syndrome and of the genetic, immune, and vascular interplay in TA, offering insights for treating CBL syndrome and broader TA.

Noonan syndrome-related myeloproliferative disorder (NS/MPD) and juvenile myelomonocytic leukemia (JMML) are rare MPDs that occur in young children. We herein report a case of NS/MPD with neonatal onset. The patient had a characteristic appearance and high monocyte count in the peripheral blood and bone marrow. Genetic testing showed the E139D mutation in PTPN11 ; however, the patient did not meet all the diagnostic criteria for JMML, and we thus diagnosed him with NS/MPD. Eight other cases of NS/MPD with neonatal onset are also summarized. The initial presentation varied, and the prognosis was considered poor compared with previous reports of NS/MPD.

Behçet\'s disease (BD) is a rare condition that is seldom associated with hematological malignancies. In this case report, we present the unique case of a 7-year-old girl diagnosed with juvenile myelomonocytic leukemia (JMML) and intestinal BD. The patient received allogeneic hematopoietic stem cell transplantation (allo-HSCT), which resulted in complete remission of both JMML and BD. Our findings suggest that allo-HSCT may be a feasible treatment option for JMML patients with coexisting BD, and holds promise for achieving remission of both illnesses. However, further clinical investigations are needed to validate these findings.

暂无摘要。

Therapy-related myeloid neoplasms (t-MN) are a distinct subgroup of myeloid malignancies with a poor prognosis that include cases of therapy-related myelodysplastic syndrome (t-MDS), therapy-related myeloproliferative neoplasms (t-MPN) and therapy-related acute myeloid leukemia (t-AML). Here, we report a series of patients with clinical features consistent with juvenile myelomonocytic leukemia (JMML), an overlap syndrome of MDS and myeloproliferative neoplasms that developed after treatment for another malignancy.

For hematopoietic stem cell transplantation to be successful, complications must be managed. Graft-versus-host disease is particularly important, but various other complications, treatment side effects, and relapse of primary disease may also occur. We report an autopsy case of juvenile myelomonocytic leukemia with a blastic crisis, in which activated and recovered autologous macrophage-related complications after cord blood transplantation caused the patient\'s death. Pathological analysis of autopsy specimens revealed diffuse infiltration of mature macrophages into the skin but scarce lymphocytes. These macrophages were found in the bone marrow interspersed with a small number of blasts that had previously occupied about 60% of the bone marrow before death. The direct cause of death was an opportunistic airway infection due to bone marrow and immune failures triggered by overactivation and proliferation of macrophages. Genetic analysis showed the activated macrophages were autologous. Together these findings indicate that the patient died from macrophage-mediated complications, but not from a blastic crisis or conventional graft-versus-host disease. When macrophage activation persists after hematopoietic stem cell transplantation, macrophage-mediated complications should be considered as a differential diagnosis. To manage this complication, pathology specimens should be examined to check for the presence of effector cells at an early stage.

Neurofibromatosis type 1 is a common multisystem autosomal dominant syndrome caused by pathogenic heterozygous variants in the neurofibromin gene (NF1). It is associated with a substantially increased cancer risk. Mosaicism for NF1 has been clinically well-established for \"second hit\" variants in skin lesions and tumor tissues. Here, we report on a 3-month-old boy with multiple café au lait macules (CAMs) and juvenile myelomonocytic leukemia (JMML) who was found to carry a previously established pathogenic NF1 variant (c.586+5G>A), as revealed by whole-exome sequencing. Surprisingly, however, this variant was detected in the homozygous state in the patient and was absent in the parents and siblings. Deep sequencing of this variant using blood, buccal swabs and skin samples was performed. As expected for an NF1 gene mutation promoting JMML, the variant was detected in 90.6% of the blood DNA reads, in sharp contrast to the mere 5% and 0.74% of reads in the saliva- and skin fibroblast-derived DNA, respectively. Our analysis, therefore, confirmed postzygotic origin of the variant followed by a mitotic event resulting in its homozygosity, although we could not differentiate between the possibilities of a gene conversion and mitotic crossover. Apparently de novo homozygous variants should trigger a careful investigation into mosaicism to achieve accurate interpretation.

BACKGROUND: Juvenile myelomonocytic leukemia (JMML) is a rare myeloproliferative neoplasm of early childhood characterized by excessive proliferation of myelomonocytic cells and an aggressive clinical course. Allogenic hematopoietic stem cell transplantation (HSCT) is a firmly established treatment, but patients without fully matched donors have poor prognoses. Disease recurrence is the main cause of treatment failure. Meanwhile, most cases with splenomegaly present with platelet transfusion refractoriness, but splenectomy remains controversial. DNA hypermethylation correlates with poor prognosis in JMML; however, hypomethylating therapy alone does not eradicate leukemic clones. Thus, a suitable treatment with a good success rate remains elusive.
UNASSIGNED: Here, we report our experience with a patient who suffered from recurrent fever, pallor, abdominal distention, leukocytosis, and thrombocytopenia with a silent past history and family history of somatic KRAS mutation. The patient was treated with decitabine as a bridging therapy before haploidentical HSCT. Decitabine was also used prophylactically after transplantation.
METHODS: We arrived at a JMML diagnosis after observing leukocytosis, less than 20% blast cells in the peripheral blood and bone marrow, increased monocyte counts, negativity for the BCR-ABL fusion gene, positivity for somatic KRAS mutation, and massive splenomegaly.
METHODS: The patient accepted splenectomy before HSCT, and haploidentical HSCT was applied after treatment with a DNA-hypomethylating agent. The hypomethylating agent was administered for 1 year after HSCT to prevent disease recurrence.
RESULTS: The patient presented with complete remission of the disease and mild graft versus host disease for 26 months after treatment with decitabine and HSCT.
CONCLUSIONS: Combining haploidentical HSCT and DNA-hypomethylating agents may improve the prognosis of JMML. Meanwhile, splenectomy could be an effective option in cases with massive splenomegaly and platelet transfusion refractoriness.

Genetic changes in juvenile myelomonocytic leukemia (JMML) determine distinct subtypes, treatments, and outcomes. JMML with germline CBL mutation and somatic NRAS mutation possibly achieves spontaneous remission, but hematopoietic stem cell transplantation is indicated for other subtypes of JMML. We hereby report a child with JMML harboring a germline CBL mutation (c.1111T>C) and an NF1 variant (c.3352A>G) concurrently. After evaluation, we considered that the NF1 variant was not the major contributor. After one year of observation, this case had no signs of disease progression. This case highlights the importance of combining available evidence and clinical findings in caring for patients with unusual genomic variations.