BackgroundBlau Syndrome (BS) is a rare autosomal dominant noncaseous granulomatous disease caused by mutations in the NOD2 gene. The disease is characterized by granulomatous dermatitis, symmetrical arthritis, and uveitis, which, if left untreated, can progress to blindness. The diagnosis of BS can be challenging because of its rarity and overlap with other rheumatologic disorders. Early detection of ocular involvement is critical to prevent vision loss and improve the prognosis of patients with BS.Case presentationIn this report, we present a case of a five-year-old Chinese girl diagnosed with BS one year ago after presenting with a systemic rash and urinary calculi. Genetic testing was recommended by a physician, and a heterozygous mutation of the NOD2 gene c.1538T > C (p.M513T) was identified. Eight months ago, due to bilateral corneal punctate opacity, we had examined and diagnosed bilateral uveitis, bilateral corneal zonal degeneration, persistent fetal vasculature (PFV) in the right eye, and perivascular granuloma in the right eye. As a result, Vitrectomy was performed on the right eye, resulting in a significant improvement in visual acuity from 1/50 on the first day after surgery to 3/10 after 1 week. After 6 months, the visual acuity of the right eye was maintained at 3/20, but opacification of the lens posterior capsule was observed. Follow-up appointments are ongoing to monitor the condition of the affected eyes. Our report underscores the importance of prompt detection and management of ocular involvement in BS accompany with PFV to prevent vision loss and improve patient outcomes.ConclusionsThis report details the case of a child diagnosed with BS who accompanied a periretinal granuloma and PFV in the right eye. Regrettably, the left eye was observed to have no light perception (NLP) with the fundus not being visible. The occurrence of ocular complications in patients with BS, must be closely monitored to prevent vision loss and enhance treatment outcomes. This case underscores the importance of prompt diagnosis and management of ocular complications in patients with BS to prevent further damage and optimize patient outcomes.