In this episode of RhAPPcast, the official podcast of Rheumatology Advanced Practice Providers, host Amanda Mixon, PA-C, is joined by Bonnie Smeryage, NP, to shed light on X-linked hypophosphatemia (XLH)—a rare hereditary condition that often goes unrecognized or misdiagnosed in rheumatology. XLH can mimic common rheumatologic and musculoskeletal disorders such as rheumatoid arthritis, ankylosing spondylitis, or fibromyalgia, leading to delayed diagnosis and treatment. Amanda and Bonnie discuss the underlying causes of XLH, key clinical red flags in both pediatric and adult patients, and the importance of ordering a fasting serum phosphorus level as part of routine evaluation for unexplained bone or joint pain. They highlight how early detection, family history, and multidisciplinary care are critical for improving patient outcomes, and why rheumatology providers are uniquely positioned to recognize and manage this condition. This conversation emphasizes the value of shared decision-making, coordinated care, and practical diagnostic strategies to ensure patients with XLH receive timely and effective treatment.