Tumeurs à cellules granuleuses multiples chez un enfant atteint d’un syndrome de Noonan compliqué de leucémie myélomonocytaire juvénile

Abstract

Granular cell tumour (GCT) is a rare form of tumour comprising Schwann cells. Herein, we report a case of a child presenting Noonan syndrome complicated by juvenile myelomonocytic leukaemia (JMML) and who also developed a multiple form of GCT. We discussed the molecular mechanisms that might account for this association. A six-year-old boy with Noonan syndrome complicated by JMML presented three asymptomatic subcutaneous nodules on his back, forearm and neck. Histological analysis revealed GCT. A literature review revealed seven cases of Noonan syndrome presenting GCT, none of which were associated with JMML. Mutation of gene PTPN11, via hyperactivation of intracellular Ras signalling may cause the development of GCT and JMML in children presenting Noonan syndrome. Detailed clinical examination is recommended in children presenting GCT to screen for multiple forms and for signs of malformation suggestive of a genetic syndrome. Ours is the first case to be described of Noonan syndrome complicated by JMML associated with multiple GCT. This association once again raises the important question of the role of the Ras-MAPK signalling pathway in the development of benign and malignant tumours of solid organs or blood, associated with genetic syndromes.