APRT (adenine phosphoribosyltransferase) catalyzes a salvage pathway reaction that converts adenine to AMP, providing an energetically efficient alternative to de novo purine synthesis 1. The enzyme functions primarily in the cytoplasm and cytosol, catalyzing adenine binding and AMP formation through its phosphoribosyltransferase activity 2. Loss of APRT function causes autosomal recessive APRT deficiency, a rare metabolic disorder characterized by hyperexcretion of 2,8-dihydroxyadenine (DHA) into urine 1. Due to DHA's low solubility, this leads to precipitation and formation of urinary crystals, stones, and crystal nephropathy 2. Clinical presentations vary widely, ranging from asymptomatic crystalluria detected on screening to severe manifestations including recurrent urolithiasis, acute kidney injury from obstructive uropathy, and progressive renal failure 32. Early diagnosis through stone analysis, crystalluria assessment, and APRT activity measurement is critical, as prompt treatment with xanthine oxidoreductase inhibitors significantly reduces DHA excretion and preserves kidney function 12. The variable clinical phenotype—even among siblings sharing identical mutations—reflects the disease's diagnostic challenge 3. Beyond renal disease, APRT participates in broader purine metabolism regulation, as demonstrated by studies showing APRT activation during viral infection and involvement in metabolic signaling pathways affecting inflammation 45.