The sparkle in her eye : A rare case of non-nephropathic cystinosis

A 40-year-old female patient presented for a routine check-up with no history of systemic illness. Her best-corrected visual acuity was 6/6 with +1.00 D presbyopic correction. Slit-lamp examination showed bilateral, uniformly diffuse, shimmering deposits or particles in the subepithelial and anterior stromal layers [Figs. 1 and 2]. The remainder of the anterior segment and fundus appeared unremarkable. Four-mirror gonioscopy and anterior segment optical coherence tomography (AS-OCT) of the cornea were performed to rule out deposits in the angles (Figs. 1 and 2 depict a normal AS-OCT of the cornea). Suspecting cystinosis, she was referred to a nephrologist for further evaluation. Renal involvement was ruled out as renal function tests were normal, leading to a diagnosis of nonnephropathic cystinosis. Cystinosis can be classified into two types: nephropathic and nonnephropathic. Ocular nonnephropathic cystinosis affects only the corneas and is caused by a mutation in the CTNS gene. This condition is inherited as an autosomal recessive disease and described as a lysosomal storage disorder.[1] Compared to the nephropathic type, this variant is rarer and primarily causes photophobia due to crystalline deposition, with no histopathological changes observed in the cornea.[2] Similarly, our patient reported no visual disturbances, and all ophthalmic as well as systemic investigations were normal. She was advised to undergo routine yearly follow-ups. A brief review of the existing literature was conducted. Biswas et al.,[3] have described both ocular nephropathic and nonnephropathic cystinosis and provided guidelines for early detection and treatment strategies. Anikster et al.,[4] determined the molecular basis for this condition and proposed mechanisms for the lack of kidney activity.Figure 1: Broad slit image of the OD depicting diffuse, shimmering deposits or particles in the subepithelial and anterior stromal layersFigure 2: Broad slit image of the OS depicting diffuse, shimmering deposits or particles in the subepithelial and anterior stromal layersThe key takeaway is to thoroughly examine, evaluate, and document such cases, as they are often asymptomatic and can be easily overlooked. Due to the rarity of the disease, diagnosis may be delayed, which can potentially impact the prognosis. It is crucial to pay attention to key symptoms, such as photophobia. Ethical approval The study was reviewed by the Institutional Ethics Committee of Aravind Eye Hospital and deemed not to require ethics approval. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship: Nil. Conflicts of interest: There are no conflicts of interest.