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Michael Marmor; Retinitis pigmentosa or severe hydroychloroquine retinopathy?. Invest. Ophthalmol. Vis. Sci. 2016;57(12):157.
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© ARVO (1962-2015); The Authors (2016-present)
Late and severe hydroxychloroquine (HCQ) retinopathy is known to mimic retinitis pigmentosa (RP) with diffuse retinal degeneration and reduced full-field ERG. A series of patients with high HCQ exposure and ERG changes compatible with RP or cone-rod dystrophy is analyzed to seek factors that can help to differentiate.
Records from 11 patients having long or excessive exposure to HCQ were reviewed and compared. Nearly half were of Asian origin. Clinical evaluations had raised the possibility of underlying or concomitant dystrophy. All had ERG recordings with significant amplitude reduction and marked delay in cone implicit time. All had SD-OCT, and most had Goldmann fields (GVF) and/or wide-field autofluorescence (FAF) images.
None cited early visual symptoms or gave a family history. ERG loss was sometimes severe, but most showed similar cone and rod involvement. Retinal degeneration was most often pericentral, but extended beyond the arcades with varying degrees of diffuse peripheral damage (but no bone-spicule pigmentation). SD-OCT was rarely useful since signs of parafoveal damage were obscured by degeneration across the macula. Peripheral field (GVF) was more preserved than might be expected from the ERG, and superior loss sometimes extended down to the disk. FAF showed less peripheral RPE loss than usual with RP and only one case showed a perifoveal glow ring.
One case seemed typical of RP, although concomitant HCQ toxicity could not be ruled out. Others showed atypical findings such as cone>rod ERG loss, distinct pericentral degeneration, surprising preservation of peripheral field and sometimes a distinct incursion of superior field loss (inferior retinal degeneration) upon the disk (which may be a useful sign). Dystrophy might in theory predispose to toxic damage, but pericentral RP is rare and not likely to explain all of these cases. The prevalence in Asian patients may reflect the fact that toxicity in Asians often begins pericentrally, and early damage may have been missed with parafoveal screening. These cases suggest that most patients with severe late HCQ exposure will show clues that implicate toxicity over dystrophy. Genetic testing could resolve this ambiguity, but at present the positive yield is too low. Occam’s razor favors one disease unless evidence for more is definitive.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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