One of the First Cases with PIK3CA-related Overgrowth Spectrum (PROS) in Saudi Arabia: A Case Report and Literature Review.

PIK3CA-related overgrowth spectrum (PROS) is an umbrella that includes a broad range of rare disorders, ranging from isolated digit enlargement to extensive overgrowth of the limbs, abdomen, or brain. One of these disorders is megalencephaly capillary malformation polymicrogyria syndrome (MCAP), which is characterized by cutaneous capillary malformations, megalencephaly, cortical brain malformations, abnormalities of somatic growth with body and brain asymmetry, developmental delay, and characteristic facial dysmorphism. The diagnosis of PROS syndrome is based on the clinical features of a patient and confirmed by a pathogenic variant in one PIK3CA allele in a biopsy of the affected tissue. However, MCAP may be diagnosed by testing a blood or saliva sample. The management of patients with MCAP syndrome includes evaluation after the initial diagnosis, treatment of manifestations, and surveillance for potential complications. To date, there is no curative treatment for patients with MCAP syndrome. Therefore, reporting such cases will help us understand them and thus develop an appropriate treatment for them. Our patient was a 46-month-old boy, who is diagnosed with MCAP syndrome. The diagnosis was based on clinical presentation, imaging studies, and whole-exome sequencing (WES). Clinically, the patient had speech and developmental delay, macrocephaly, joint hyperlaxity, unsteady gait, and subtle dysmorphic facial features. The facial features include low-set ears, frontal bossing, depressed nasal bridge, and bilateral esotropia. MRI studies showed megalocephaly, bilateral perisylvian polymicrogyria, bilateral peri-regional, high T2 signal intensities, and cerebellar tonsil ectopia with crowding of the posterior fossa. Finally, the diagnosis was confirmed by WES, which detected changes in the PIK3CA gene. The patient is on overgrowth protocol for PIK3CA, which includes alpha-fetoprotein and abdominal ultrasound every three months until the age of eight years. To the best of our knowledge, this is one of the first cases of PROS in Saudi Arabia, which illustrates the classical findings of MCAP syndrome. Further studies and investigations on PROS syndrome are needed to aid in making a definitive classification and treatment of such complex and rare diseases.