Juvenile myelomonocytic leukemia

Juvenile Myelomonocytic Leukemia in a Child: A Case Report of Palliative Chemotherapy and Literature Review Applied to Limited Resources Centers

Juvenile myelomonocytic leukemia (JMML) is a rare hematopoietic malignancy in children, with an incidence of 1.2 per million children per year. At this moment, we present a case report and a brief literature review of JMML in a child, primarily focused on its applicability in low-middle income countries. A 3.5-year-old male was referred to our tertiary center due to pallor, enlarging abdomen and neck mass, recurrent fever, and chronic diarrhea. Initial laboratory workup showed hemoglobin of 6.4 g/dl, white blood cell of 315.62 × 103/μL, and platelet of 17 × 103/μL. Blood smears showed 10% suspected blasts, 17% myelocytes, and 17% metamyelocytes with thrombocytopenic crisis. The HbF level was 5.8%. BCR-ABL gene tested negative. The patient was diagnosed with juvenile myelomonocytic leukemia. Considering that HSCT could not be done in our center and lack other financial possibilities to seek treatment abroad, the family agreed to do the palliative treatment. The patient was treated with oral 6-mercaptopurine and subcutaneous cytarabine. Four weeks after receiving 6-mercaptopurine, the white blood cell count decreased to 10.6 × 103/μL and the spleen size was half of the original size. The patient continued chemotherapy until week 15, chemotherapy was stopped, but 16 weeks after the diagnosis of JMML, he developed severe thrombocytopenia, endophthalmitis, and sepsis and passed away. As a conclusion, in JMML cases in developing countries without HSCT, palliative chemotherapy is acceptable, and palliative care is an important aspect.

Clinical parameter-based prediction of DNA methylation classification generates a prediction model of prognosis in patients with juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is a rare heterogeneous hematological malignancy of early childhood characterized by causative RAS pathway mutations. Classifying patients with JMML using global DNA methylation profiles is useful for risk stratification. We implemented machine learning algorithms (decision tree, support vector machine, and naïve Bayes) to produce a DNA methylation-based classification according to recent international consensus definitions using a well-characterized pooled cohort of patients with JMML (n = 128). DNA methylation was originally categorized into three subgroups: high methylation (HM), intermediate methylation (IM), and low methylation (LM), which is a trichotomized classification. We also dichotomized the subgroups as HM/IM and LM. The decision tree model showed high concordances with 450k-based methylation [82.3% (106/128) for the dichotomized and 83.6% (107/128) for the trichotomized subgroups, respectively]. With an independent cohort (n = 72), we confirmed that these models using both the dichotomized and trichotomized classifications were highly predictive of survival. Our study demonstrates that machine learning algorithms can generate clinical parameter-based models that predict the survival outcomes of patients with JMML and high accuracy. These models enabled us to rapidly and effectively identify candidates for augmented treatment following diagnosis.

Single-Center Experience With Epigenetic Treatment for Juvenile Myelomonocytic Leukemia

Background: Juvenile myelomonocytic leukemia (JMML) is a rare myelodysplastic/myeloproliferative neoplasm diagnosed in young children, characterized by somatic or germline mutations that lead to hyperactive RAS signaling. The only curative option is hematopoietic stem cell transplantation (HSCT). Recent data showing that aberrant DNA methylation plays a significant role in pathogenesis and correlates with clinical risk suggest a possible benefit of hypomethylating agents (HMA) in JMML treatment.

Aim: The aim is to report the results of HMA-based therapy with 5-azacytidine (AZA) in three JMML patients treated in a single center, non-participating in EWOG-MDS study.

Methods: The diagnosis and treatment response were evaluated according to international consensus criteria. AZA 75 mg/m² intravenous (i.v.) was administered once daily on days 1–7 of each 28-day cycle. All patients were monitored for hematologic response, spleen size, and evolution of extramedullary disease. Targeted next generation sequencing (NGS) were performed after the 3rd AZA cycle and before SCT to evaluate the molecular alterations and genetic response.

Results: Three patients diagnosed with JMML were treated with AZA (off-label indication) in Pediatric Department of Fundeni Clinical Institute, Bucharest, Romania between 2017 and 2019. There were two females and one male with median age 11 months, range 2–16 months. The cytogenetic analysis showed normal karyotype in all patients. Molecular analysis confirmed KRAS G13D mutation in two patients and NRAS G12D mutation in one patient. The clinical evaluation showed important splenomegaly and hepatomegaly in all 3 pts. One patient received AZA for early relapse after haploidentical HSCT and the other two patients received upfront AZA, as bridging therapy before HSCT. After HMA therapy, 2/3 patients achieved clinical partial response (cPR), 1/3 had clinical stable disease (cSD) and all had genetic stable disease (gSD) after 3 cycles and were able to receive the planned HSTC. One patient achieved clinical and genetic complete response before HSCT. During 22 cycles of AZA there were only four adverse events but only one determined dose reduction and treatment delay.

Conclusion: Our data show that AZA monotherapy is safe and effective in controlling disease both in upfront and relapsed patients in order to proceed to HSCT.

How I treat juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is a unique, aggressive hematopoietic disorder of infancy/early childhood caused by excessive proliferation of cells of monocytic and granulocytic lineages. Approximately 90% of patients carry either somatic or germline mutations of PTPN-11, K-RAS, N-RAS, CBL, or NF1 in their leukemic cells. These genetic aberrations are largely mutually exclusive and activate the Ras/mitogen-activated protein kinase pathway. Allogeneic hematopoietic stem cell transplantation (HSCT) remains the therapy of choice for most patients with JMML, curing more than 50% of affected children. We recommend that this option be promptly offered to any child with PTPN-11-, K-RAS-, or NF1-mutated JMML and to the majority of those with N-RAS mutations. Because children with CBL mutations and few of those with N-RAS mutations may have spontaneous resolution of hematologic abnormalities, the decision to proceed to transplantation in these patients must be weighed carefully. Disease recurrence remains the main cause of treatment failure after HSCT. A second allograft is recommended if overt JMML relapse occurs after transplantation. Recently, azacytidine, a hypomethylating agent, was reported to induce hematologic/molecular remissions in some children with JMML, and its role in both reducing leukemia burden before HSCT and in nontransplant settings requires further studies.

Natural history and early diagnosis of LAD-1/variant syndrome

The syndrome of leukocyte adhesion deficiency (LAD) combined with a severe Glanzmann-type bleeding disorder has been recognized as a separate disease entity. The variability in clinical and cell biological terms has remained largely unclear. We present data on 9 cases from 7 unrelated families, with 3 patients being actively followed for more than 12 years. The disease entity, designated LAD-1/variant syndrome, presents early in life and consists of nonpussing infections from bacterial and fungal origin, as well as a severe bleeding tendency. This is compatible with 2 major blood cell types contributing to the clinical symptoms (ie, granulocytes and platelets). In granulocytes of the patients, we found adhesion and chemotaxis defects, as well as a defect in NADPH oxidase activity triggered by unopsonized zymosan. This last test can be used as a screening test for the syndrome. Many proteins and genes involved in adhesion and signaling, including small GTPases such as Rap1 and Rap2 as well as the major Rap activity-regulating molecules, were normally present. Moreover, Rap1 activation was intact in patients' blood cells. Defining the primary defect awaits genetic linkage analysis, which may be greatly helped by a more precise understanding and awareness of the disease combined with the early identification of affected patients.

The mutational spectrum of PTPN11 in juvenile myelomonocytic leukemia and Noonan syndrome/myeloproliferative disease

Germ line PTPN11 mutations cause 50% of cases of Noonan syndrome (NS). Somatic mutations in PTPN11 occur in 35% of patients with de novo, nonsyndromic juvenile myelomonocytic leukemia (JMML). Myeloproliferative disorders (MPDs), either transient or more fulminant forms, can also occur in infants with NS (NS/MPD). We identified PTPN11 mutations in blood or bone marrow specimens from 77 newly reported patients with JMML (n = 69) or NS/MPD (n = 8). Together with previous reports, we compared the spectrum of PTPN11 mutations in 3 groups: (1) patients with JMML (n = 107); (2) patients with NS/MPD (n = 19); and (3) patients with NS (n = 243). Glu76 was the most commonly affected residue in JMML (n = 45), with the Glu76Lys alteration (n = 29) being most frequent. Eight of 19 patients with NS/MPD carried the Thr73Ile substitution. These data suggest that there is a genotype/phenotype correlation in the spectrum of PTPN11 mutations found in patients with JMML, NS/MPD, and NS. This supports the need to characterize the spectrum of hematologic abnormalities in individuals with NS and to better define the impact of the PTPN11 lesion on the disease course in patients with NS/MPD and JMML.