Severe Cerebral Small Vessel Disease Caused by the Uniallelic p.A252T Variant of HTRA1

OBJECTIVE: To investigate the clinical effect of a heterozygous missense variant of HTRA1 on cerebral small vessel disease (CSVD) in a large Japanese family with a p.A252T variant. METHODS: We performed clinical, laboratory, radiologic, and genetic evaluations of members of a previously reported family with cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL). RESULTS: Two family members were previously reported patients with CARASIL. Among 6 uniallelic p.A252T carriers, 2 had neurologic symptoms with brain MRI abnormalities, 2 showed CSVD on the MRI only, and the other 2 were unaffected. Clinical phenotypes of 2 heterozygous patients were comparable with those of patients with CARASIL, whereas the other 3 heterozygous patients had developed milder and later-onset CSVD. One heterozygous carrier was asymptomatic. DISCUSSION: Previous studies have suggested that uniallelic p.A252T causes disease. However, our study revealed that patients with uniallelic p.A252T can have severe and young-onset CSVD. The clinical manifestations of uniallelic variant carriers were highly variable, even within the same family. Male and atherosclerotic risk factors were considered to be additional factors in the severity of neurologic symptoms in uniallelic p.A252T carriers, suggesting that strict control of vascular risk factors can prevent vascular events in uniallelic HTRA1 carriers.