Aneurysm, intracranial berry, 12 is a vascular condition characterized by the development of berry aneurysms within the cerebral arteries. Research has identified a link with variants in the THSD1 gene, which is thought to be important for maintaining the structure of blood vessel walls. This condition is inherited in an autosomal dominant pattern, meaning that inheriting one altered copy of the gene can increase the risk of developing the condition. Although precise prevalence estimates are not available, it is recognized as part of the spectrum of cerebrovascular disorders.

Individuals with this condition most commonly develop cerebral berry aneurysms, with reports indicating that this feature is seen in up to 80-99% of cases. In addition, a significant proportion may experience subarachnoid hemorrhage if an aneurysm ruptures, while a smaller subset shows signs of arterial fibromuscular dysplasia, fusiform cerebral aneurysms, or internal carotid artery dissection. The clinical presentation can include sudden and severe headaches or other neurological symptoms, prompting further evaluation through imaging studies. Not all individuals experience all features, and severity varies considerably.

The underlying cause of aneurysm, intracranial berry, 12 is associated with pathogenic variants in the THSD1 gene. THSD1 is believed to contribute to the structural integrity of blood vessels, and disruptions in its function can predispose affected individuals to aneurysm formation. This condition is inherited in an autosomal dominant pattern, meaning that a single altered copy of the gene can increase risk. It is important to understand that not every individual with a THSD1 variant will develop symptoms, reflecting incomplete penetrance and variable expressivity. Families are encouraged to seek genetic counseling to better understand the implications for family members. Associated genes include THSD1.