Occult macular dystrophy in an Italian family carrying a mutation in the RP1L1 gene

Abstract

Occult macular dystrophy (OMD) is an inherited macular disease characterized by progressive visual decline with the absence of visible retinal abnormalities. Typical alterations of the retinal structure are detectable by spectral domain optical coherence tomography (SD-OCT). Mutations in the RP1L1 gene have been identified to be responsible for the disease in Asian subjects. The present study assessed the role of mutations in the RP1L1 gene in an Italian family with OMD. One patient with OMD and five related subjects (two male offspring affected by progressive visual decline and three asymptomatic siblings of the patient) were subjected to complete ophthalmological examination. SD-OCT was also performed. All subjects were screened for OMD-associated genetic mutations in the RP1L1 gene. The OMD patient and the two symptomatic offspring presented with a reduced best-corrected visual acuity. Although no fundus abnormalities were observed, SD-OCT examination showed that the external limiting membrane and the inner segment/outer segment band were not clearly identifiable and a focal disruption of the photoreceptor layer was present. The degree of photoreceptor alterations was correlated with the severity of visual impairment. Clinical and tomographic results in the three asymptomatic relatives were normal. A p.Arg45Trp mutation in the RP1L1 gene was identified in the OMD patient, in the two symptomatic offspring and also in two of the asymptomatic siblings of the patient. The identification of RP1L1 mutations in subjects with OMD may improve the accuracy of diagnosis of this rare condition and may aid in enhancing the efficacy of genetic counseling.