Northern blot analyses have delineated cystatin D's expression as predominantly localized to the parotid gland, exhibiting a more restricted tissue distribution compared to the ubiquitously expressed cystatin C. Despite cystatin C's established role as an early and sensitive biomarker for CKD, facilitating diagnosis especially in scenarios where creatinine is inadequate [62], the implications of cystatin D in renal pathology remain underexplored. Here, CST5 is linked to chronic kidney disease.