Abstracts

Rationale: Phosphatidylinositol-4,5-bisphospate 3-kinase, catalytic subunit alpha (PIK3CA) related overgrowth spectrum (PROS) is named to encompass the segmental overgrowth disorders due to somatic mutations in PIK3CA. It has been suggested that somatic PIK3CA mutations in most patients with isolated lymphatic malformation are also related to their neurologic dysfunction. Methods: A 7-year-old boy has been treated for epilepsy and mental retardation combined with cystic lymphangioma. He has been on antiepileptic drugs to control seizures. In addition, neuropsychologic therapy has been applied to improve his cognitive function but unfortunately, he has still mild degree of mental retardation. Since 3 years old, lymphangioma on his right anterolateral neck has been resected three times but he had a relapse of lymphangioma eventually. To detect somatic mutation of PIK3CA on tissue of lymphangioma, we analyzed and compared PIK3CA mutation from his lymphangioma tissue and blood by using mutant enrichment with 3'-modified Oligonucleotides-quantitative PCR and could find PIK3CA mutation only from lymphangioma tissue. Finally, the patient has been diagnosed with PROS referenced by the clinical diagnostic criteria suggested by experts at the recent National Institutes of Health sponsored Workshop. Results: Now, we have a plan to apply everolimus, an analogue of rapamycin, to prevent regrowth of lymphangioma and improve his neurologic dysfunctions including seizures and cognitive deterioration by reducing an excessive activation of mTOR signaling pathway. Conclusions: The recognition of the new entity called PROS, along with the potential for genetic testing, now allows physicians to recognize and confirm diagnosis of the condition and to anticipate better management for the potential clinical problems. Funding: none