Juvenile myelomonocytic leukemia displays mutations in components of the RAS pathway and the PRC2 network.

Juvenile myelomonocytic leukemia (JMML) is a rare and severe myelodysplastic and myeloproliferative neoplasm of early childhood initiated by germline or somatic RAS-activating mutations. Genetic profiling and whole-exome sequencing of a large JMML cohort (118 and 30 cases, respectively) uncovered additional genetic abnormalities in 56 cases (47%). Somatic events were rare (0.38 events/Mb/case) and restricted to sporadic (49/78; 63%) or neurofibromatosis type 1 (NF1)-associated (8/8; 100%) JMML cases. Multiple concomitant genetic hits targeting the RAS pathway were identified in 13 of 78 cases (17%), disproving the concept of mutually exclusive RAS pathway mutations and defining new pathways activated in JMML involving phosphoinositide 3-kinase (PI3K) and the mTORC2 complex through RAC2 mutation. Furthermore, this study highlights PRC2 loss (26/78; 33% of sporadic JMML cases) that switches the methylation/acetylation status of lysine 27 of histone H3 in JMML cases with altered RAS and PRC2 pathways. Finally, the association between JMML outcome and mutational profile suggests a dose-dependent effect for RAS pathway activation, distinguishing very aggressive JMML rapidly progressing to acute myeloid leukemia.

Inherited CARD9 deficiency in 2 unrelated patients with invasive Exophiala infection.

BACKGROUND: Exophiala species are mostly responsible for skin infections. Invasive Exophiala dermatitidis disease is a rare and frequently fatal infection, with 42 cases reported. About half of these cases had no known risk factors. Similarly, invasive Exophiala spinifera disease is extremely rare, with only 3 cases reported, all in patients with no known immunodeficiency. Autosomal recessive CARD9 deficiency has recently been reported in otherwise healthy patients with severe fungal diseases caused by Candida species, dermatophytes, or Phialophora verrucosa. METHODS: We investigated an 8-year-old girl from a nonconsanguineous Angolan kindred, who was born in France and developed disseminated E. dermatitidis disease and a 26 year-old woman from an Iranian consaguineous kindred, who was living in Iran and developed disseminated E. spinifera disease. Both patients were otherwise healthy. RESULTS: We sequenced CARD9 and found both patients to be homozygous for loss-of-function mutations (R18W and E323del). The first patient had segmental uniparental disomy of chromosome 9, carrying 2 copies of the maternal CARD9 mutated allele. CONCLUSIONS: These are the first 2 patients with inherited CARD9 deficiency and invasive Exophiala disease to be described. CARD9 deficiency should thus be considered in patients with unexplained invasive Exophiala species disease, even in the absence of other infections.

Juvenile myelomonocytic leukaemia and Noonan syndrome.

BACKGROUND: Infants with Noonan syndrome (NS) are predisposed to developing juvenile myelomonocytic leukaemia (JMML) or JMML-like myeloproliferative disorders (MPD). Whereas sporadic JMML is known to be aggressive, JMML occurring in patients with NS is often considered as benign and transitory. However, little information is available regarding the occurrence and characteristics of JMML in NS. METHODS AND RESULTS: Within a large prospective cohort of 641 patients with a germline PTPN11 mutation, we identified MPD features in 36 (5.6%) patients, including 20 patients (3%) who fully met the consensus diagnostic criteria for JMML. Sixty percent of the latter (12/20) had severe neonatal manifestations, and 10/20 died in the first month of life. Almost all (11/12) patients with severe neonatal JMML were males. Two females who survived MPD/JMML subsequently developed another malignancy during childhood. Although the risk of developing MPD/JMML could not be fully predicted by the underlying PTPN11 mutation, some germline PTPN11 mutations were preferentially associated with myeloproliferation: 10/48 patients with NS (20.8%) with a mutation in codon Asp61 developed MPD/JMML in infancy. Patients with a p.Thr73Ile mutation also had more chances of developing MPD/JMML but with a milder clinical course. SNP array and whole exome sequencing in paired tumoral and constitutional samples identified no second acquired somatic mutation to explain the occurrence of myeloproliferation. CONCLUSIONS: JMML represents the first cause of death in PTPN11-associated NS. Few patients have been reported so far, suggesting that JMML may sometimes be overlooked due to early death, comorbidities or lack of confirmatory tests.

[Juvenile myelomonocytic leukemias]. / Les leucémies myélomonocytaires juvéniles.

Juvenile myelomonocytic leukemias (JMML) are rare but severe myelodysplastic and myeloproliferative neoplasms of infancy. They represent about 10 new cases per year in France and preferentially affect males. JMML are all stem cell diseases the common denominator of which is RAS pathway dysregulation, due to mutations in RAS (NRAS, KRAS) or RAS regulatory components (PTPN11, NF1 or CBL). This leads to an hypersensivity of myeloid progenitors to GM-CSF (granulo-macrophagic colony stimulating factor) which induces in turn excessive monocytic and macrophagic proliferation in blood and bone marrow. All organs can be infiltrated by this monocytic proliferation leading to multisystemic failure. Blast crisis with transformation into acute myeloid leukemia occurs in one third of patients. A salient feature of JMML is their frequent association with predisposition syndromes such as Noonan syndrome, neurofibromatosis and CBL syndrome, which are developmental diseases associated with a constitutional RAS pathway deregulation, now grouped under the name RASopathies. Clinical heterogeneity makes JMML diagnosis difficult. Splenomagaly is the most constant sign. Palor, adenopathy, respiratory or cutaneous symptoms can also be present. Blood smear shows monocytosis (>1×10(9)/L) presence of myeloid progenitors and abnormal basophils. The demonstration of an endogeneous in vitro growth of myeloid progenitors although not very specific can help JMML diagnosis. Nowadays, genetic typing has to be included in the workup of JMML diagnosis and allows to evidence a mutation in more than 90% of cases. JMML have a poor prognosis. The only curative treatment is bone marrow transplantation but approximately 35% of patients relapse. JMML clinical course is highly heterogeneous and unpredictable. Some rare patients have an indolent evolution or even spontaneous remission. Age over two years, thrombopenia below 33×10(9)/L and high foetal hemoglobin (HbF) level for age are poor prognosis criteria but hardly predict individual outcome. Several research directions are currently being explored to improve prognosis prediction and provide more effective targeted treatments.

Genetic typing of CBL, ASXL1, RUNX1, TET2 and JAK2 in juvenile myelomonocytic leukaemia reveals a genetic profile distinct from chronic myelomonocytic leukaemia.

JMML and CMML are rare myelodysplastic/myeloproliferative neoplasms occurring at both ends of life. To investigate relationships between JMML and CMML, genes recently involved in CMML were studied in 68 JMML patients. Mutations in TET2, RUNX1 and JAK2(V617F) are involved in myelodysplastic and/or myeloproliferative syndromes, and more specifically in CMML but were not found in JMML. Pangenomic analysis by SNP-array showed no abnormality at these loci. Three frameshift mutations of ASXL1 leading to a truncated protein were found in three patients (4%) with late onset JMML displaying also RAS activating mutations. Homozygous mutations of CBL with 11q loss of heterozygosity were found in five (7%) JMML. CBL substitutions were different from those reported in CMML, exclusive from other RAS activating mutations, and were germline in all patients. Overall, the pattern of genetic lesions observed in JMML differed from that of CMML. Although signalling deregulation is involved in CMML, transcriptional deregulation seems to play a pivotal role, with mutation of RUNX1, ASXL1 or TET2. Conversely, none of these genes involved in transcription or chromatin remodelling was found to be significantly altered in JMML, while CBL mutations confirm the central role of RAS and growth factor signalling deregulation in JMML.

Report of two cases of aseptic meningitis with persistence of pneumococcal cell wall components in cerebrospinal fluid after Pneumococcal meningitis.

We describe two cases of aseptic meningitis occurring some time after pneumococcal meningitis. Both cases may have resulted from an inflammatory response to persistent pneumococcal cell membrane components, as the cerebrospinal fluid samples were positive by the Binax NOW Streptococcus pneumoniae antigen test. Potential mechanisms and diagnostic impact are discussed.