Crystalline keratopathy in nephropathic cystinosis.

Abstract

A 3-year-old male child presented with complaints of poor weight gain, delayed motor milestones since 1 year of age and features suggestive of rickets (wrist widening, bowing of legs and Harrison’s sulcus). He was third born of a third degree consanguineous marriage, had polyuria, with investigations revealing proximal renal tubular acidosis and generalised aminoaciduria (Fanconi syndrome). Eye evaluation revealed both the cornea to be studded with yellow-golden crystals throughout their surface. The crystals appeared to occupy the epithelial and superficial stromal layers of the cornea, and were distributed in a generalised fashion (Figure 1). Fundus evaluation of both the eyes too showed crystalline deposits within the retina (not cooperative for fundus imaging). Genetic studies confirmed the diagnosis of cystinosis with pathogenic CTNS gene mutations on intron 9 and exon 11. Younger sibling aged 2 years had a similar clinical presentation, and his genetic studies also determined the same pathogenic CTNS gene mutations. Cystinosis is a rare autosomal recessive metabolic disorder characterised by accumulation of cystine in lysosomes. Kidneys and eyes are, especially, vulnerable though eventually the disease impacts all the organs including liver, muscles, white blood cells and central nervous system. CTNS, located on the short arm of the chromosome 17 (p13), is the responsible gene. It encodes the lysosomal cystine carrier cystinosin [1,2]. There are three clinical forms of cystinosis-infantile (nephropathic) cystinosis; late-onset cystinosis and benign cystinosis. Infantile cystinosis is the most severe and the most common type of cystinosis, but may be missed initially as all