Introduction Juvenile myelomonocytic leukemia (JMML) is a rare childhood neoplasm (<5% cases), which has been categorized under myelodysplastic/myeloproliferative neoplasms (MDS/MPN) in the recent classification by the World Health Organization. Methods We developed a 51‐gene (151.5kB) low‐cost targeted myeloid panel based on single‐molecule molecular inversion probes to comprehensively evaluate the genomic profile of Juvenile myelomonocytic leukemia (JMML). Results A total of 50 children with clinical and pathological features of JMML were sequenced at high coverage. Among the 50 patients, 44(88%) harbored mutations in one of the RAS/MAPK‐pathway genes, most frequently in NRAS (32%), followed by PTPN11 (28%) and NF1 (22%). One‐fifth of children had more than one mutation, with 5 cases harboring two RAS pathway mutations. Monosomy 7 was detected in 32% (16) patients, and five of these did not harbor any RAS pathway mutations. Children with monosomy 7 showed shorter overall survival compared with their wild‐type counterparts (P = .02). Conclusion Our study highlights that comprehensive genomic profiling identifies at least one mutation in almost 90% of JMML patients. Performing genomic analysis at baseline might help in triaging children with JMML for allogenic stem cell transplant in resource‐constrained settings.

Background: JMML is a pediatric haematopoietic stem cell malignancy characterised by uncontrolled proliferation of myelomonocytic and progenitor compartments and a poor outcome. We comprehensively evaluated the genomic profile of JMML that presented to our hospital for diagnosis and treatment. Procedure: We developed a 51-gene (151.5kB) low-cost targeted myeloid panel based on single-molecule molecular inversion probes. A total of 50 children with clinical and pathological features of JMML were sequenced at high coverage on an Illumina MiSeq. The presenting clinical, laboratory and follow-up data were procured from the electronic medical record system of the institution. Results: The median age of our cohort was 2 years, with a male preponderance. Among the 50 patients, 43 (86%)harboured mutations in one of the RAS/MAPK-pathway genes, most frequently in PTPN11 (14, 28%), and NRAS (14, 28%), followed by NF1(11. 22%). Interestingly, 20% (10) of children had more than one mutation, with 5 cases harbouring two RAS-pathway mutations. Monosomy 7 was detected in 32% ( 16) patients, and five of these did not harbour any RAS-pathway mutations. The follow-up data revealed that 37 (74%) of these children had succumbed to the disease. Children with monosomy 7 showed shorter overall survival, compared to their wildtype counterparts (p=0.02). Conclusion: Our study highlights that comprehensive genomic profiling identifies at least one mutation in almost 90% of JMML patients. Performing genomic analysis early in evaluation of JMML might help in triaging patients for allogenic stem cell transplant in resource-constrained settings.