Nasopharyngeal Cystine Crystal Deposition Postrenal Transplant: Case Report and Review of a Rare Cystinosis Manifestation.

IntroductionCystinosis is a rare autosomal recessive lysosomal storage disorder characterized by pathologic cystine accumulation in various tissues. While renal involvement is well-documented, extrarenal manifestations, particularly in the nasopharynx, are exceptionally rare.Patient PresentationA 27-year-old Saudi female patient with a history of cystinosis and renal transplantation presented with unilateral tinnitus, vertigo, and nasal obstruction. Nasopharyngoscopy revealed a nasopharyngeal mass. Histopathologic examination of the nasopharyngeal tissue demonstrated numerous histiocytes containing distinctive hexagonal, rectangular, and rhomboid-shaped crystals with birefringence under polarized light, confirming nasopharyngeal cystine crystal deposition. Treatment with intranasal corticosteroids and saline irrigations provided symptomatic relief.ConclusionThis report represents only the second documented instance of nasopharyngeal cystinosis, expanding the known spectrum of extrarenal manifestations of cystinosis. It highlights the importance of considering cystinosis in the differential diagnosis of nasopharyngeal masses in affected patients and demonstrates the diagnostic value of polarized light microscopy in identifying characteristic cystine crystals.