NOONAN SYNDROME-LIKE DISORDER WITH OR WITHOUT JUVENILE MYELOMONOCYTIC LEUKEMIA (CBL VARIANT-ASSOCIATED SYNDROME)

The CBL gene (Cas-Br-M (murine) ecotropic retroviral transforming sequence) is a proto-oncogene whose protein, E3 ubiquitin-protein ligase CBL, functions as a negative regulator of several signal transduction pathways including the Ras/MAP kinase signal transduction pathway. Somatic variants and translocations of this gene are found in many cancer types, including acute myeloid leukemia. The CBL gene is located on chromosome 11q23.

Juvenile myelomonocytic leukemia (JMML) is a rare form of leukemia in infancy and early childhood which is characterized by malignant transformation in the hematopoietic stem cell compartment. JMML accounts for 30% of myelodysplastic syndrome cases and 2% of all leukemias. 10 to 15% of children affected by neurofibromatosis type 1 with associated pathogenic variants in the neurofibromin gene develop JMML. Patients with Noonan syndrome or Noonan syndrome-like disorder due to germline alterations in the PTPN11, KRAS, and NRAS genes also have a predisposition to JMML. Isolated forms of JMML may include somatic PTPN11 variants as well as homozygous CBL variants.

In a few patients presenting with symptoms of Noonan syndrome, in whom pathogenic variants in genes typical for Noonan syndrome have been excluded, germline variants in the CBL gene can be detected. Most of these occur de novo. These patients may have concurrent JMML. This has been shown to be caused by a subsequent somatic LOH (loss of heterozygosity) on chromosome 11q23, where the CBL gene is located.

References

Zenker et Kutsche 2016, medgen 28:15 / Bulow et al. 2015 Am J Med Genet 167A:394 / Martinelli et al. 2010, Am J Hum Genet 87:250 / Perez et al. 2010, J Med Genet 47:686 / Niemeyer et al. 2010, Nature Genet 42:794 / De Filippi et al. 2009, Brit J Haematol 147:706 / Schubbert et al. 2006, Nature Genet 38:331 / Jongmans et al. 2005, Am J Med Genet 134A:165