From perfect visual function to ‘legally’ blind in one year: new mutations in progressive cone dystrophy

Abstract

PurposeWe aim to report a case of a 15 year‐old patient with severe and rapid bilateral visual impairment due to progressive cone dystrophy and describe the associated mutations.MethodsThis is a case report of a patient with a rare disease who underwent full ophthalmologic evaluations including optical coherence tomography (OCT) of the posterior pole, fundus autofluorescence (FAF) and electroretinography (ERG).ResultsA 15‐year‐old girl was presented at our Department with progressive vision loss and poor colour vision complaints. The patient reported these complaints for a year, despite a full uneventful ophthalmic evaluation at that time. Best‐corrected visual acuity was 6/60 for each eye and Ishihara 24‐plates colour test was altered. Fundoscopic evaluation showed a maculopathy with spotty pigment changes in addition to temporal pallor of the optic disk. Posterior pole OCT showed a reduced outer nuclear layer and retinal pigment epithelium unspecific changes. FAF revealed a central dark area surrounded by a ring of increased autofluorescence. ERG was inconclusive due to poor collaboration, although it was hypothesised to have a slight cone dysfunction. Moreover, genetic analyses of ABCA4 and CDHR1 genes were found to be positive for multiple mutations. The c.6816 + 2T>A (p.Leu2035Pro) mutation was never described and the c.6104T>C (p.Leu2035Pro) mutation was only present in one patient with Stargardt disease. After a period of 2 years of follow‐up visual function and retinal disease remained stable.ConclusionsProgressive cone dystrophy is a rare inherited ocular disorder characterized by the loss of cone cells. This case report emphasizes the need to reach a clear diagnosis when uncommon symptoms appear in an otherwise normal ophthalmic evaluation and also describe newer mutations in ABCA4 gene enhancing our knowledge about this disease.