Figure 2.

(a) Light microscopy renal biopsy images of adenine phosphoribosyltransferase (APRT) deficiency. Hematoxlyn and eosin stain (H&E; original magnification ×20) of the 3-month protocol transplant biopsy of case 1 showing ongoing crystal deposits, predominantly in the tubular lumen (black arrows) and associated with foreign body reaction and acute tubular injury. Crystals also are seen within the epithelial layer in some of the injured or atrophic tubules (red arrows). One tubule demonstrated the disruption of the tubular basement membrane and the release of crystalline material into the intersititum (yellow arrow). (b) Polarized image of the renal biopsy (of Figure 1a) demonstrating birefringent crystals and highlighting the locations of the crystals, which are more subtle on the H&E sections. The areas of tubular rupture and the release of crystals into the interstitium are highlighted (yellow arrows). Bar = 100 μm. (c) Electron microscopy of APRT deficiency demonstrating luminal obstruction with the crystalline aggregates. Bar = 5000 nm. (d) Higher-power view of the electron microscopy image within the luminal aggregate (in Figure 2c) revealing needle-like substructures. Bar = 1000 nm. (e) Crystalluria in APRT deficiency. Typical appearance of spherical, brown crystals seen on urine microscopy at original magnification of ×20. (f) Crystalluria in APRT deficiency under polarized light demonstrating birefringent crystals with a maltese cross pattern at original magnification of ×40.