Impaired Kidney Function With Kidney Tubular Vacuolization and Crystals in Adult Refsum Disease: A Case Report

Adult Refsum disease is a rare hereditary peroxisomal disorder characterized by impaired phytanic acid metabolism. The accumulation of phytanic acid in tissues, especially adipose and neural, is believed to contribute to disease manifestations. Clinically apparent kidney dysfunction has been reported in only 2 cases. We describe a 55-year-old woman with adult Refsum disease, who was referred to nephrology for impaired kidney function without proteinuria. Kidney biopsy showed vacuolization of proximal tubular epithelium and unremarkable glomeruli. Focally, distal tubular cytoplasm showed variably sized crystals with ultrastructural laminated substructures (or "paracrystalline formation"). To the best of our knowledge, the light microscopy for these crystals in a peroxisomal disease has not been previously described, and adult Refsum disease has not been described as a significant metabolic kidney disorder. These unique morphologic features contribute to the spectrum of findings in this rare genetic condition. This case also demonstrates the value of kidney function monitoring and therapeutic plasma exchange for these patients.