In our study, we describe the first case of a somatic pathogenic variant in PTPN11 causing a congenital and progressive LO phenotype with vascular proliferation mimicking diffuse capillary malformation with overgrowth/Klippel–Trenaunay syndrome and characterized by development of cerebral astrocytoma in infancy. The gene discussed is PTPN11; the disease is cerebral astrocytoma.