Ocular Cystinosis in a routine Ophthalmologic Evaluation

Cystinosis is a rare autosomal recessive metabolic disease, with an incidence ranging from 1:100,000 to 1:200,000. It occurs by chromosomal mutation, in which a defect in the active transport of cystine across the lysosomal membrane allows the accumulation of this amino acid in lysosomes [1]. As a result, cystine can form crystals in various tissues such as the kidneys, pancreas, thyroid, testicles, bone marrow, brain, eye, and muscles [2].
Three phenotypic forms of cystinosis are described: Infantile nephropathic form - more common and more severe, usually associated with Fanconi syndrome and need for kidney transplantation in the first decade of life; Juvenile nephropathic form - later onset and less severe; Non-nephropathic form - more currently called ocular cystinosis, benign in character, usually with isolated, asymptomatic ophthalmologic findings, and may present from adolescence to the fifth decade of life [3].
The ocular symptoms of cystinosis result from the deposition of cystine crystals. The crystals are deposited mainly on the cornea and conjunctiva. In the cornea, the deposits are located in the periphery and anterior stroma, and as the disease progresses, the crystals move centripetally posteriorly [2]. The deposits may also affect the corneal epithelium, which may be related to the foreign body sensation reported by some patients6 The deposits become increasingly dense without proper treatment, causing photophobia and worsening of visual acuity [3,5].
Cystinosis may present with other ocular manifestations such as retinitis pigmentosa, macula ridge deposits, posterior syncytia, glaucoma, and hemorrhagic retinopathy. In all cases, there is a risk of worsening visual acuity [1]. Ocular complications may be associated with the progression of the systemic disease, so regular and multidisciplinary follow-up is important.
Treatment should be done with oral and topical cysteamine. The ocular treatment can be done with cysteamine solution 0.55% (used continuously 02/02h). Currently, the use of this solution has shown good results, and therefore it should be prescribed in all cases of cystinosis with ocular involvement [1].