Phosphate, fractures and frustration – A Missed Diagnosis of Oncogenic Osteomalacia Leading to Multisystem ComplicationDr Ryan Wilson – GMC: 8007097Dr Lydia Sturridge GMC: 4528829Frimley Health Foundation TrustFrimley Park Hospital Portsmouth Road Frimley, Camberley Surrey GU16 7UJ United KingdomAuthor contribution statementDr. Ryan Michael Wilson (Corresponding Author) Frimley Park Hospital NHS Foundation Trust, Emergency Medicine, Portsmouth Road, Frimley, Frimley, UK GU16 7UJ Email: ryanwilson9998@gmail.com ORCID iD: 0009-0004-1783-7402 Contributions: Project administration, writing – original draft, writing – review and editing.Dr. Lydia Sturridge Frimley Park Hospital NHS Foundation Trust, Emergency Medicine, Portsmouth Road, Frimley, Frimley, UK GU16 7UJ Email: lydia.sturridge@nhs.net Contributions: Writing – review and editing.Consent:Written informed consent was obtained from the patient for publication of this case report in accordance with the journal’s patient consent policy.Key clinical message:Persistent hypophosphataemia must prompt thorough evaluation. This case highlights the severe, multi-system consequences of delayed recognition of oncogenic osteomalacia. Early biochemical assessment, imaging, and multidisciplinary involvement are critical to avoid misdiagnosis and prevent irreversible complications such as skeletal fragility and cardiomyopathy.Introduction:Oncogenic osteomalacia, or tumour-induced osteomalacia (TIO), is a rare paraneoplastic syndrome caused by renal phosphate wasting due to excess fibroblast growth factor 23 (FGF23) secreted by phosphaturic mesenchymal tumours (PMTs). Resulting in hypophosphataemia, osteomalacia, muscular weakness, and bone pain¹, this condition is often misdiagnosed due to nonspecific symptoms and the difficulty in locating the tumour².This report details the prolonged diagnostic journey of a 44-year-old mechanic whose symptoms were misattributed to mechanical causes. It underscores the importance of an early biochemical assessment, imaging, and multidisciplinary collaboration to prevent late-stage complications.Case history and examination:Chronic pain, progressive weakness, and height loss are unusual in a 44-year-old male. Delayed diagnosis resulted from a failure to consider symptoms holistically and a postponed biochemical workup. Despite a history of worsening functional decline, his symptoms were repeatedly attributed to mechanical osteoarthritis and chronic pain syndrome due to a previous road traffic accident years prior. His analgesic regime consisted of oral morphine, amitriptyline, naproxen, and gabapentin.Multiple medical professionals could not identify a diagnosis that, if recognized earlier, could have prevented skeletal deterioration and cardiac involvement. This case highlights the need to investigate persistent hypophosphataemia and adopt a multisystem approach to avoid mistaking metabolic bone disease for chronic pain.This gentleman, X, first sought medical attention for worsening exertional dyspnoea, with paroxysmal nocturnal dyspnoea and bilateral lower-limb swelling over approximately six months. His partner also noted increasing fatigue, even on mild exertion. Initially, such symptoms were attributed to hypertension and deconditioning; however, the severity of this raised concerns for a systemic illness.His initial cardiovascular assessment revealed a blood pressure of 155/105, and an N-terminal Pro-B type Natriuretic peptide (BNP) of greater than 2000 ng/L. An electrocardiogram (ECG) yielded a left ventricular hypertrophy (LVH) pattern, with associated T-Wave inversion in the anterolateral distribution. Moreover, a transthoracic echocardiogram (TTE) confirmed a dilated left ventricle at 6.3 cm, with an ejection fraction of roughly 30%, consistent with a diagnosis of dilated cardiomyopathy (DCM). Given the emerging links between phosphate metabolism and myocardial function³, this was an early opportunity to formally assess his phosphate levels.At the same time, his ‘arthritic’ pain was worsening – namely in his back, hips, and ankles – necessitating the use of crutches to ambulate. Four years prior to his presentation in the clinic, he had suffered a road traffic accident, leading to assumptions that such discomfort was related to injuries and subsequent arthritic change. Despite this, he deteriorated from this perspective; with arthritis severe enough in his right ankle to consider fusion surgery. At this time, no further metabolic bone assessment was considered.Differential diagnoses, investigation and treatment:
