A 38-year-old woman of African-American descent presents with a 6-month history of progressive facial disfigurement. Examination reveals bluish-purple indurated plaques on the nose, cheeks, and ears (marked **A** in the diagram). She reports chronic nasal congestion and recent vision changes. Imaging shows bilateral hilar lymphadenopathy and pulmonary fibrosis. Biopsy of the facial lesion demonstrates non-caseating granulomas. Which of the following systemic complications is this patient at HIGHEST risk of developing given the chronic nature of the lesions marked **A**?