Finally, the patient diagnosed with Klippel-Trenaunay syndrome, with splenic and hepatic haemangiomas and telangiectatic lesions of the right hindquarter (discussed above), was found to have a somatic mosaic mutation in PIK3CA. This patient is now being recruited to EPIK, a randomised controlled study of the PI3K inhibitor, alpelisib, for treatment of PIK3CA overgrowth syndromes. Here, PIK3CA is linked to Klippel-Trénaunay syndrome.