A 47-year-old woman was referred to the rheumatology department at Lille University Hospital (Lille, France) in September 2019, following 3 months of bone pain and muscle weakness. She had persistently low serum phosphate (0.4mmol/L [0.8-1.4]) and normal serum calcium and parathyroid hormone levels. Bone alkaline phosphatase was high (80µg/l [4.7-27.1]) and 25-OH-vitamin D slightly lower than normal (24ng/mL [30-60 ng/mL]).