Branch Retinal Artery Occlusion as the First Manifestation of Bartonella henselae Infection

Bartonella henselae is a gram-negative rod bacterium that causes cat scratch disease (CSD) in humans, with the most common manifestation being Parinaud’s oculoglandular syndrome. A 37-year-old healthy man with an unremarkable ocular history presented with an acute painless scotoma over the superonasal visual field of the right eye (RE) for 1 week following a cat scratch two weeks before presentation. His visual acuity was 6/12 over the RE and 6/9 over the left eye (LE), with a normal anterior segment examination bilaterally. Fundus examination showed a retinitis patch occluding the right inferotemporal branch with a surrounding pale retina and isolated retinitis was seen superior to the left macula. Fundus fluorescein angiography of RE showed a non-filling defect along the inferotemporal artery branch with the absence of flow distal to the filling defect which signified an occlusion area. Parafoveal vasculitis changes were seen over the LE. Intraretinal fluid over the right macula was detected on optical coherence tomography. Laboratory testing revealed positive Bartonella henselae IgM with IgG titers greater than 1:512. The patient received oral azithromycin for 6 weeks and demonstrated good clinical response. Branch retinal artery occlusion is an uncommon presentation of CSD. Early diagnosis and prompt intervention are essential to restore visual function and prevent further complications.