Cystinosis

It is an inherited lysosomal storage disorder where a congenital defect in the cystinosin transport protein impairs the efflux of the amino acid 'cystine' from lysosomes, causing it to crystalize intracellularly and trigger widespread tissue necrosis, notably in renal tubular cells.

Cystine crystals initially deposit within the renal proximal tubules. The damaged kidneys fail to reabsorb essential nutrients, water, sodium, potassium, and phosphate, excessively excreting them into the urine (Renal Fanconi Syndrome). Consequently, the child experiences insatiable thirst (polydipsia), massive urine output (polyuria), and metabolic bone disease (rickets).

Following renal involvement, ocular tissues are predominantly affected. Cystine crystals progressively accumulate in the cornea (the transparent anterior segment of the eye). This manifestation induces severe photophobia (light sensitivity), an acute gritty sensation, and excessive lacrimation in the pediatric patient.

Clinical suspicion arises in infants presenting with failure to thrive and polyuria. An ophthalmological slit-lamp examination revealing pathognomonic corneal cystine crystals strongly supports the diagnosis. Definitive diagnosis is confirmed by quantifying leukocyte cystine levels via blood analysis or through molecular genetic testing (identifying CTNS gene mutations).

Yes. Lifelong administration of 'Cysteamine', a cystine-depleting agent, is required (typically dosed four times daily) to facilitate the clearance of cystine from the cells. This pharmacotherapy significantly delays or halts organ deterioration. Topical cysteamine eye drops are utilized to dissolve corneal crystals. If diagnosis is delayed and end-stage renal failure occurs, a Renal Transplantation is imperative (the disease does not recur in the grafted kidney).