ABSTRACT

Autosomal dominant hypophosphatemic rickets (ADHR) is a rare metabolic bone disease with variable clinical presentation, caused by pathogenic variants in the FGF23 gene. The disease typically manifests in childhood with growth retardation and rickets symptoms, but may also be diagnosed in adolescence or adulthood with atypical symptoms. We present a 14-year and 5-month-old female patient who presented with bilateral sacral insufficiency fractures following a subtle onset without a history of trauma. Diagnostic tests revealed findings consistent with hypophosphatemic rickets and a de novo heterozygous c.526C>T (p.Arg176Trp) variant in the FGF23 gene, leading to a diagnosis of ADHR. The patient had no significant history of rickets during childhood. She had lived for approximately one year with complaints of progressive pain in the lower lumbar region, which worsened with walking and sitting, without receiving a diagnosis. Bilateral sacroiliac insufficiency fractures and hypophosphatemia were detected, and genetic analysis was performed. The patient underwent bilateral sacroiliac fracture fixation by pediatric orthopedics, and phosphate and active vitamin D (calcitriol) therapy was initiated by pediatric endocrinology. Clinical symptoms improved significantly during follow-up. Due to its genetic and clinical heterogeneity, autosomal dominant hypophosphatemic rickets (ADHR) is a disease that can cause delays in diagnosis. The number of cases reported in the literature associated with this variant is limited, and this is, to the best of our knowledge, the first report of an adolescent with ADHR diagnosed with bilateral sacral insufficiency fractures. This case is important for raising awareness of ADHR and highlighting the broad clinical spectrum of the disease. Sharing the diagnostic and treatment processes will be helpful for clinicians encountering this rare disease.