Last Week's Medical Mystery

 A 14-year-old previously healthy girl presents with a complaint of decreasing vision in her left eye for the past week. She has no orbital pain, and an examination of her pupils, extra-ocular muscles, conjunctivae, sclera, iris and anterior chamber is normal. She is afebrile, and a general examination is unremarkable. She is an animal lover. This is a photograph of her left retina.



















DIAGNOSIS: Lieber's stellate neuroretinitis caused by Bartonella henselae, the most common bartonella species to cause Cat Scratch disease (CSD). Fortunately, the neuroretinitis, which presents as a sudden painless loss of vision, usually resolves in several months without residual. Involvement of the external eye - Parinaud's oculoglandular syndrome - can also occur with or without neuroretinitis. The most common presentation of CSD is acute or chronic tender lymphadenopathy in the region draining a scratch or bite. A 0.5 to 1.0 cm papule, nodule, or vesicle may occur at the site of the inoculation. Systemic manifestations, including fever, malaise, anorexia, headache, myalgias, and abdominal pain are variably present. Rare complications include encephalitis, peripheral nerve abnormalities, myelitis, facial nerve palsy, and granulomatous hepatitis or splenitis. Cats acquire the organism from fleas, and can have high levels of asymptomatic bacteremia, particularly when they are kittens. Azithromycin is an effective treatment.  
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