Abstract: SA-PO936
Impaired Kidney Function with Renal Tubular Vacuolization and Paracrystals in Adult Refsum Disease: A Case Report
Session Information
- Pathology and Lab Medicine - 2
October 26, 2024 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Pathology and Lab Medicine
- 1800 Pathology and Lab Medicine
Authors
- Lee, Chen Yu (Jamie), Department of Pathology, University of British Columbia, Vancouver, British Columbia, Canada
- Elliott, Mark, Division of Nephrology, University of British Columbia, Vancouver, British Columbia, Canada
- Lehman, Anna, Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
- Mcrae, Susanna A., Department of Pathology, University of British Columbia, Vancouver, British Columbia, Canada
- Riazy, Maziar, Department of Pathology, University of British Columbia, Vancouver, British Columbia, Canada
Introduction
Classic, or adult, Refsum disease (ARD) is a rare peroxisomal disorder characterized by an inability to metabolize the fatty acid phytanic acid (PA). Accumulation of PA leads to polyneuropathy and potentially lethal cardiac arrhythmias. Renal impairment is rarely seen and there is a paucity of information on the histopathology. We present a case of renal impairment due to tubular involvement by ARD.
Case Description
A 55-year-old Fijian female with genetically proven ARD presented with a reduced eGFR without proteinuria or overt tubular dysfunction . Her past medical history includes ARD-related retinitis pigmentosa, DM2, recent MI with PCI, and chronic knee osteoarthritis. Physical examination showed shortened toes consistent with ARD. Serum PA at diagnosis was 180 mcg/mL (ULN 3 mcg/mL).
A renal biopsy was performed to assess for diabetic nephropathy versus another cause for her renal impairment. The biopsy showed diffuse vacuolization of renal tubular epithelium, with rare foci of intracytoplasmic crystals (Figure 1A). Ultrastructurally, these crystals were electron dense with unusual parallel linear arrays (or ‘paracrystalline formation’) (Figure 1B).
She continues to be very adherent to her low PA diet and avoidance of fasting, but despite this has experienced a progressive decline in her eGFR. Her PA level remains elevated at 270 mcg/mL.
Discussion
To the best of our knowledge, this is the first description of intracytoplasmic crystals on light microscopy in ARD. The etiology and pathologic effects of these crystals are not yet known, but they may share features with other crystalline nephropathies. This case provides evidence to support renal function monitoring in ARD, which is currently not suggested by the literature. The morphology of the intracytoplasmic crystals are rather distinct but subtle and can be overlooked. Nephropathologists should be vigilant for additional findings in the setting of tubular epithelial abnormalities without a known explanation. Limiting dietary PA is the first-line treatment of choice but may not be sufficient to prevent complications.