Autosomal dominant inheritance of a heterozygous mutation in HTRA1: A case report and literature review.

RATIONALE: Heterozygous mutations in the gene encoding HtrA serine protease 1 (HTRA1) can cause autosomal dominant cerebral small-vessel disease (CSVD), presenting with clinical features that differ slightly from other hereditary CSVD subtypes. Only a limited number of cases have been documented globally. PATIENT CONCERNS: A 51-year-old man presented with more than 2 years of left lower limb weakness, which had acutely worsened over the preceding day. Brain magnetic resonance imaging (MRI) revealed ischemic demyelinating changes in the white matter. DIAGNOSES: Genetic sequencing identified a heterozygous HTRA1 mutation. Follow-up testing confirmed that both of his daughters also carried the same heterozygous mutation. INTERVENTIONS: Management focused on secondary prevention, risk-factor control, and lifestyle modification. OUTCOMES: A 6-month follow-up cranial MRI showed no new lesions, and the patient remained clinically stable without disease progression during 1 year of monitoring. LESSONS: Heterozygous HTRA1 mutations may present as autosomal-dominant CSVD, and genetic testing is central to establishing the diagnosis.