Patients with PROS (PIK3CA-Related Overgrowth Spectrum) can suffer disfiguring, function-limiting, and life-threatening effects1
For many patients with PROS, overgrowth is sizable and highly visible. For others, however, it may take less overt forms, like vascular malformation. Regardless, PROS can significantly compromise the functional capabilities of even very young patients and can cause life-threatening complications.2-4 Although survival data have not been reliably reported, early mortality has been observed in case reports.2

DVT, deep vein thrombosis; PE, pulmonary embolism.
References:
- Keppler-Noreuil KM, Rios JJ, Parker VER, et al. PIK3CA-related overgrowth spectrum (PROS): diagnostic and testing eligibility criteria, differential diagnosis, and evaluation. Am J Med Genet A. 2015;167A(2):287-295.
- Parker VER, Keppler-Noreuil KM, Faivre L, et al. Genet Med. 2019;21(5):1189-1198.
- Keppler-Noreuil KM, Sapp JC, Lindhurst MJ, et al. Clinical delineation and natural history of the PIK3CA-related overgrowth spectrum. Am J Med Genet A. 2014;164A(7):1713-1733.
- Mirzaa G, Conway R, Graham JM Jr, Dobyns WB. PIK3CA-related segmental overgrowth. In: Adam MP, Ardinger HH, Pagon RA, et al, eds. GeneReviews® [Internet]. Seattle, WA: University of Washington, Seattle; 1993-2019.
- Rodriguez-Laguna L, Ibanez K, Gordo G, et al. CLAPO syndrome: identification of somatic activating PIK3CA mutations and delineation of the natural history and phenotype. Genet Med. 2018;20(8):882-889.
- National Institutes of Health. Klippel-Trenaunay syndrome. Genetics home reference. https://ghr.nlm.nih.gov/condition/klippel-trenaunay-syndrome. Accessed March 20, 2020.