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Case history crucial component of rubella retinopathy diagnosis
This patient was exposed to her mother's German measles during gestation.
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A 49-year-old African-American woman presented for examination for an updated spectacle prescription. The patient’s ocular history was positive for a previous diagnosis of familial dominant drusen in both eyes without complications and stable moderate compound myopic astigmatism with presbyopia in both eyes, according to her previous records.
She reported bilateral congenital sensorineural hearing loss and epilepsy, which was being treated with oxcarbazepine. The patient denied any other systemic conditions and denied being on any other medications.
Her entering visual acuities were 20/20 OD, 20/20 OS with her habitual spectacle correction. Entrance testing and slit lamp examination were within normal limits in both eyes, and her IOP with Goldman applanation tonometry was 18 mm Hg OU. Dilated fundus exam revealed a mix of diffuse hypo- and hyperpigmented retinal pigmented epithelial disruption in the posterior poles of both eyes. Fundus autofluorescence (FAF) images highlight this retinal pigmented epitheliopathy as well. Given the previous diagnosis of familial dominant drusen and the lack of a typical/expected retinal appearance of familial dominant drusen, further investigation was considered and sought.
Upon revisiting the case history, the patient reported that her mother had contracted German measles when she was pregnant with her, which led to the patient’s sensorineural hearing loss. Given this information, rubella retinopathy was now strongly suspected. Multifocal electroretinograms (ERG) were normal in both eyes, rapid plasma reagin was non-reactive, fluorescent treponemal antibody absorption was negative, rubella IgG was significantly elevated, and the rubella IgM was negative. This confirmed our suspicion of rubella retinopathy.
The rubella virus is from the Togavirdiae family of viruses found only in humans. The disease state is commonly referred to as rubella but is also occasionally referred to as German measles. Rubella viruses are typically transmitted in adults via respiratory droplets but can also be passed transplacentally from an infected mother to her unborn fetus. There are significant ocular and systemic complications, first recognized by Gregg in 1941, that can occur as a consequence of infection.
Congenital rubella syndrome
The last major worldwide pandemic occurred in 1963 to 1965, which makes most patients approximately 50 to 55 years of age at the time of this article. During this last pandemic, 10% of all pregnant women were infected, and 30% of those pregnancies resulted in systemic abnormalities that resulted in congenital rubella syndrome (CRS), according to Duszak.
The classic triad of CRS is reported to be: congenital cardiopathy (30%) sensorineural deafness (60%) and ocular defects (30% to 50%). In the U.S., 95% of the population is seropositive due to our vaccination efforts beginning in 1969 (Yoser et al., Duszak, Khandekar et al., Arnold). The accompanying table highlights the risk of fetal complications secondary to rubella infection.
Rubella infection usually only leads to CRS in non-immune mothers who are exposed during the first trimester of pregnancy. If the mother has appropriate immunity prior to becoming pregnant, the risk of CRS for the fetus is virtually zero. Maternal IgG is the only Ig that can cross the placenta, but this occurs only around 8 weeks gestation at the earliest. Fetal IgG synthesis does not begin until the second trimester (20 to 24 weeks). When these timelines of immune system protection are compared to the first 16 weeks of gestation, it becomes apparent that the fetus’ immunological protection is weakest during this time, which means an acquired rubella infection in the first trimester to a non-immune mother poses the biggest risk to the fetus, leading to the complications associated with CRS.
Ocular defects
The main ocular defects associated with CRS usually include: rubella retinopathy (60%), nuclear cataracts (27%), microphthalmia (10% to 20%) and glaucoma (10% to 15%) (Yoser et al., Duszak, Khandekar et al., Arnold). Other ocular complications can include: strabismus/amblyopia, refractive errors (hyperopia more commonly than myopia) and iris atrophy. The iris atrophy accounts for CRS patients being notoriously poor dilators.
Rubella retinopathy (also sometimes called salt-and-pepper retinopathy), the most common ocular complication of CRS, can be considered pathognomonic for prenatal rubella infection and occurs bilaterally in 80% of cases (Yoser et al., Duszak, Arnold, Weiter et al., Golberg et al.). Studies have shown that the retinopathy is nonprogressive and confined to the retinal pigment epithelium (RPE) layer of the retina, as the neural retina and choroid are unaffected. Normal electroretinogram, color vision, visual fields and visual acuity are expected. Despite choroidal neovascular membrane (CNVM) being a rare complication with rubella retinopathy, it should be ruled out at every ocular exam.
Intravenous fluorescein angiography (IVFA) has been used in rubella retinopathy to assess suspected CNVM formation, but unless CNVM is suspected, there is no reason to perform this test routinely. Recently, FAF has been shown to noninvasively highlight areas of dysfunctional RPE in rubella retinopathy (Goldberg et al.). Therefore, some authors suggest that FAF can be sufficient to establish the diagnosis of rubella retinopathy in the absence of IVFA.
Differential diagnoses
The biggest differential diagnoses for this condition tend to be: familial/dominant drusen, syphilitic chorioretinopathy, diseases toxic to the RPE and retinitis pigmentosa (sine pigmento) with Usher’s syndrome. Appropriate lab work and electrophysiologic testing in conjunction with an astute clinical exam can help eliminate unlikely diagnoses.
This patient’s management
Is the seropositivity of our patient’s rubella IgG titer a result of vaccination or previous exposure during her gestational development? After all, the measles-mumps-rubella (MMR) vaccine is a standard vaccination for children today. Therefore, the IgG can be persistently high in anyone who has been given the MMR vaccine in the past. However, we do not think this affects our new rubella retinopathy diagnosis in this patient.
Based on the patient’s retinal findings, lack of tests to support alternate diagnoses and the history of her mother contracting the rubella virus during the patient’s gestation, our diagnosis of rubella retinopathy makes the most sense. Fortunately, no specific therapy is indicated for rubella retinopathy, so periodic retinal examinations are all that is needed in the majority of cases.
This case highlights the importance of a thorough case history to help navigate differential diagnoses with certain ocular presentations. This case could serve as a good example of the importance of considering other possible diagnoses when typical findings associated with a previously diagnosed condition do not necessarily fit the entire clinical picture.
- References:
- Alford, CA. Yale J Biol Med. 1982;55:187-192.
- Arnold J. Curr Opin Ophthalmol. 1995;6(3):45-50.
- Duszak RS. Optometry. 2009;doi:10.1016/j.optm.2008.03.006.
- Goldberg N, et al. Ocul Immunol Inflamm. 2009;doi:10.3109/09273940903118634.
- Khandekar R, et al. Arch Ophthalmol. 2004;122:541-545.
- Orth DH, et al. Br J Ophthalmol. 1980;doi:10.1136/bjo.64.3.201.
- Weiter JJ, et al. Inf Dis Clin N Amer. 1992;6:875-891.
- Yoser SL, et al. Surv Ophthalmol. 1993;37:313-352.
- For more information:
- Christopher J. Borgman, OD, FAAO, is an assistant professor at the Southern College of Optometry in Memphis. He can be reached at cborgman@sco.edu.
- Mary Hoang, OD, is an instructor at the Southern College of Optometry. She can be reached at mhoang@sco.edu.
Disclosures: The authors report no relevant financial disclosures.