Abstract: FR-PO446
Hypophosphatemia and Avascular Necrosis Requiring Hip Replacement in a 24-Year-Old due to SLC9A3R1 Mutation
Session Information
- Pediatric Nephrology - I
November 04, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
Abstract Time: 10:00 AM - 12:00 PM
Category: Genetic Diseases of the Kidneys
- 1102 Genetic Diseases of the Kidneys: Non-Cystic
Authors
- Khan, Ayesha Anwar, Mayo Clinic, Jacksonville, Florida, United States
- Aslam, Nabeel, Mayo Clinic, Jacksonville, Florida, United States
- Mao, Michael A., Mayo Clinic, Jacksonville, Florida, United States
Introduction
Phosphorus is involved in a variety of biological activities, and hypophosphatemia can result in a range of clinical multiorgan symptoms that can vary in severity. Hypophosphatemia can be due to decreased intestinal absorption, increased urinary excretion, or transcellular movement into cells.
Case Description
We report case of a 31-year-old female with history of bilateral distal femoral head avascular necrosis requiring right hip replacement at age 24, vitamin D deficiency, and nephrolithiasis who presented for evaluation of hypophosphatemia of 2.4. Laboratory studies showed creatinine 0.76, calcium 9.2, phosphorus 2.8, 25-hydroxy vitamin-D level 13, PTH 60, magnesium 2.2, and albumin 4.1. Urinalysis showed a bland sediment without proteinuria.
Imaging included DEXA scan that was appropriate for age, x-ray of left knee demonstrated sclerotic areas in the distal femur and proximal tibia, and CT showing no nephrolithiasis in setting of patient reported passed stones. She was referred to clinical genomics. Genetic testing showed she was heterozygous for a variant in the SLC9A3R1 gene (mode of inheritance autosomal dominant).
Discussion
SLC9A3R1 (SLC9A3 Regulator 1) encodes a sodium/hydrogen exchange regulatory cofactor and is part of a group of rare hereditary renal phosphate wasting disorders. Heterozygous missense and splice site variants of the SLC9A3R1 gene have been reported in individuals with autosomal dominant hypophosphatemic nephrolithiasis/osteoporosis type 2, which is characterized by impaired renal phosphate reabsorption in the renal proximal tubules. This gene mutation can be associated with hypophosphatemia, nephrolithiasis, bone demineralization, and osteoporosis.
This report illustrates a case of avascular necrosis of long bones associated with SLC9A3R1 gene mutation and highlights that early genetic testing may improve long-term outcomes and complications. Increased genetic testing will also allow further studies to investigate the penetrance and clinical relevance of SLC9A3R1 variants on clinical management and outcomes.