Late-onset retinal oxalosis in primary hyperoxaluria type 2

Abstract

Purpose: To report a previously undescribed case of late-onset vision loss due to retinal oxalosis in a patient with primary hyperoxaluria type 2 (PH2).

Observations: An 82-year-old female with a history of biopsy-proven oxalate nephropathy developed vision loss 8 months after end stage kidney disease. She developed progressive retinal ischemia secondary to crystal deposition. She was presumed to have retinal oxalosis, and genetic testing confirmed PH2. Her retinopathy occurred once renal clearance fellow below hepatic oxalate production. The only effective treatment is kidney transplantation, but this patient was not a candidate.

Conclusions and importance: To date, this is the most delayed-onset and severe reported case of progressive ischemic retinopathy from PH2. Patients with systemic oxalosis should be referred for genetic testing, as there are new RNA interference treatments approved for other subtypes of primary hyperoxaluria.

Keywords: Crystalline retinopathy; Primary hyperoxaluria type 2; Retinal oxalosis.

Fig. 1

Renal Biopsy and Function. A. H&E stained renal biopsy section shows mild interstitial fibrosis and tubular atrophy. Under polarized light, calcium oxalate microcrystals (bright regions) are visible in tubular lamina and in the interstitium. Scale = 50 μm. B. Estimated glomerular filtration rate (eGFR, CKD-EPI 2021) over time. The patient had a nephrectomy at age 15. Her remaining kidney function slowly began to decline in 2020 at age 89. There was a sharp decline in March 2022, approximately 1 year prior to onset of vision symptoms. It is believed that systemic oxalosis occurs after eGFR falls below 30–40 mL/min/1.73m2 because hepatic oxalate production exceeds renal removal. A renal biopsy confirmed oxalate nephropathy 8 months prior to vision symptoms. Patient started dialysis 6 months before vision symptoms.

Fig. 2

Retinal Imaging at Presentation and 9 months. A-B. Fundus photographs at presentation show macular pigment mottling, cotton wool spots, and intravascular and retinal fine crystal deposition in both eyes. A′-B’. Optical coherence tomography (OCT) at presentation reveals diffuse hyperreflective foci (white arrows) and few sub-retinal pigment epithelium (RPE) deposits (yellow arrow). C-D. Fundus photographs 9 months after presentation reveal a dramatic increase in crystalline deposits intraarteriolarly and intraretinally. C′-D’. OCT at 9 months shows increased intraretinal hyperreflective foci. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 3

Multimodal Imaging of Hyperreflective Foci at 1 month. A. Magnified photo of the macula shows intra-arteriolar, intraretinal, and subretinal deposits. B. OCT angiography en-face deep capillary plexus slab demonstrates remarkable deep capillary plexus flow voids with diffuse hyperreflective foci. C-D. Structural line scans show locations of these hyperreflective foci in the retina (white and yellow arrows). (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)