JAN 04, 2012
The authors of this study published in the December 2011 issue of the Journal of Neuro-Ophthalmology report an unusual case of infectious optic neuropathy following infection with endemic typhus (Rickettsia typhi). Optic neuropathy is rarely associated with R. typhi, and postinfectious optic neuropathy is even less common. This case is also noteworthy because optic neuropathy is rarely associated with the significant degree of visual loss experienced by this patient without evidence of chorioretinal abnormalities and because his visual symptoms developed weeks after successful recovery from the acute illness.
The patient, a 63-year-old white man, was hospitalized for serologically-confirmed endemic typhus two months prior to experiencing visual symptoms. R. typhi is a flea-borne bacterial disease rarely found in most of the developed world. Known ocular manifestations linked to endemic typhus include mild vitritis, retinal lesions and retinal vascular leakage.
During the patient’s hospitalization, he experienced a high fever, diffuse maculopapular rash and delirium. He subsequently developed hepatic and renal failure, meningoencephalitis and pancytopenia secondary to hemophagocytosis. Extensive testing for infectious, inflammatory and infiltrative etiologies was negative except for R. typhi titers for IgM (1:8192) and IgG (1:256). He was treated with systemic doxycycline and a tapering course of intravenous corticosteroids. The patient was discharged after completely recovering from multiorgan failure.
Three weeks later, he presented to the emergency room with acute painless visual loss in the right eye. Visual acuity was 20/800 in the right eye and 20/25 in the left eye. There was a right relative afferent pupillary defect. Slit-lamp biomicroscopy showed no anterior uveitis. Extraocular movements, external examination and intraocular pressures were normal. Ophthalmoscopy revealed mild vitritis and optic disc edema in the right eye while the left fundus was normal. The left optic disc had a cup-to-disc ratio of 0.3. Automated visual fields showed a central scotoma and the mean deviation (MD) of −11.38 dB on the right eye while the left visual field was normal. Fluorescein angiography showed mild right optic disc leakage.
Three months later, the patient’s visual acuity was 20/200 in the right eye. The right optic disc was pale, and optical coherence tomography of the right eye showed decreased peripapillary retinal nerve fiber layer thickness of 70 mm (normal: 100 ± 10 mm). Repeat right visual field testing (automated 24-2) demonstrated an MD of −0.74 dB, with reduction in the size and density of the central scotoma.
The authors conclude that the absence of the typical R. typhi ocular findings suggests a different pathogenesis in the postinfectious state or possibly that the patient’s fundus abnormalities had resolved by the time of examination. They say that the exact mechanism of the endemic typhus–associated optic neuropathy is unknown but probably immune-related, ashe timing of visual loss supports an immunological mechanism. They conclude that treatment of postinfectious optic neuropathy with high-dose corticosteroids appears reasonable but should be avoided during active infection.