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

This article focuses on a rare extrarenal manifestation of cystinosis, a genetic lysosomal storage disorder caused by mutations in the CTNS gene leading to cystine accumulation in tissues. It presents the case of a 27-year-old Saudi female with cystinosis and a history of renal transplantation who developed a nasopharyngeal mass associated with tinnitus, vertigo, and nasal obstruction. Histopathologic examination revealed cystine crystal deposition within nasopharyngeal histiocytes, confirmed by birefringence under polarized light microscopy. This case represents only the second documented instance of nasopharyngeal cystinosis, expanding the known spectrum of extrarenal involvement and underscoring the importance of considering cystinosis in the differential diagnosis of nasopharyngeal masses in affected patients. The report highlights the diagnostic value of tissue biopsy and polarized light microscopy in identifying cystine crystals and calls for increased awareness of atypical presentations as patient survival improves.