Biallelic loss-of-function variants in <i>PTGIS</i> cause recurrent cervical internal carotid artery vasospasm

BACKGROUND: Recurrent cervical internal carotid artery vasospasm (RCICAV) is a rare cause of ischemic stroke in young adults. However, its pathophysiology remains largely unknown. RCICAV is a life-threatening condition, sometimes accompanied by coronary spasmodic angina in addition to severe stroke, highlighting the need for further investigation of its etiology and therapeutic approaches. AIMS: This study aimed to identify the genetic basis of Japanese families harboring RCICAV. METHODS: Whole-exome and Sanger sequencing analyses were performed in five Japanese patients from four families (two affected siblings and three unrelated sporadic patients) and seven unaffected members from three families enrolled from October 2016 to May 2025. RCICAV was diagnosed using magnetic resonance angiography, which demonstrated vasospasm of the cervical portion of the internal carotid artery during the event and normalization during remission. In vitro and ex vivo analyses of the detected variants were performed to verify functional deficiencies. RESULTS: gene, which encodes the prostacyclin synthase. Three splice-site and nonsense variants, c. 1358+2 T>C, p.W39X, and p. E314X, were identified in five patients from four families in either homozygous or compound heterozygous states. The c.1358+2T>C variant caused exon 9 skipping (p.V403Ifs*24), which was confirmed by a minigene assay and reverse transcription polymerase chain reaction using RNA extracted from peripheral blood leukocytes of a homozygous patient. Human carotid artery endothelial cells expressing these truncated variants exhibited markedly reduced PTGIS protein and prostacyclin metabolite production. CONCLUSIONS: The results indicate that prostacyclin synthase deficiency is the core pathology of RCICAV. Given that prostacyclin is a potent vasodilator, impaired biosynthesis is consistent with the disease mechanism and may serve as a promising therapeutic target to prevent life-threatening events, including severe stroke and angina.