Fig. 3: Algorithm for the diagnosis of X-linked hypophosphataemia.
From: Clinical practice recommendations for the diagnosis and management of X-linked hypophosphataemia
Patients usually present with rickets or osteomalacia and concomitant hypophosphataemia. The differential diagnosis is based on the mechanisms leading to hypophosphataemia, namely, high parathyroid hormone (PTH) activity (leading to calcipenic rickets or osteomalacia), inadequate phosphate absorption from the gut or renal phosphate wasting (leading to phosphopenic rickets or osteomalacia). A family history of X-linked inheritance with full penetrance in female carriers strongly supports the diagnosis of X-linked hypophosphataemia (XLH), which can be confirmed by genetic testing. FGF23, fibroblast growth factor 23; LMW, low molecular weight.
