Hereditary Paraganglioma - SDHB at 1p36 / SDHD at 11q23

A 28-year-old woman presents with headaches, palpitations, and a painless neck mass at the carotid bifurcation. Duplex ultrasound shows a highly vascular mass with the characteristic "lyre sign" splaying the internal and external carotid arteries. MR angiography confirms a 3.5 cm carotid body paraganglioma. Plasma metanephrines and 24-hour urine metanephrines are normal, but plasma methoxytyramine is elevated. Her father died at age 42 from metastatic abdominal paraganglioma, and a paternal uncle had bilateral glomus jugulare tumors. Genetic testing identifies a germline pathogenic variant in SDHB at the locus marked **A** in the diagram. Which of the following best characterizes the inheritance pattern and malignancy risk associated with mutations at this locus?