Endocrine Abstracts

Background: Metastatic disease is common in bone, with the majority occurring in the spine, pelvis, and long bones such as the femur and humerus. Acrometastasis, a term used to describe malignant spread distal to the elbow and knee, is a pattern less commonly seen. Its rarity often leads to delayed diagnosis; the condition may be confused with more common conditions such as inflammatory arthritis and Charcot neuroarthropathy, the latter especially in particular in patients with diabetes mellitus. This can lead to poor patient outcomes, with a serious impact on survival.

Case Presentation: An 80-year-old lady with type 2 diabetes mellitus and a history of previous non-invasive papillary carcinoma of the bladder, previously documented to be in remission, presented to her general practitioner with left foot pain following trauma. Initial radiographs were normal, prompting a diagnosis of a simple sprain. 3 months later, the patient was referred to the orthopaedic team due to worsening pain. Examination revealed erythema and swelling, but pulses were present and no neuropathy was detected. Repeat x-rays revealed lytic lesions in the talus and navicular bones. MRI confirmed a lytic and proliferative defect and was reported as likely acute Charcot arthropathy with superimposed infection, leading to subsequent referral to the diabetes team. Charcot arthropathy was also considered the most probable diagnosis when imaging was reviewed by specialists in two separate multidisciplinary team meetings. Bone biopsy was recommended as part of the further work-up given the patient’s history; this demonstrated sheets of malignant tumour cells in keeping with metastatic transitional cell carcinoma. The patient was subsequently diagnosed with pedal acrometastasis from her existing malignancy, an infrequently described entity within the medical literature.

Discussion: This case identifies and draws awareness to a rare complication of malignancy, as well as highlights the importance of maintaining an open differential diagnosis in suspected Charcot arthropathy; a complication of diabetes that is often misdiagnosed, impacting patient morbidity and mortality¹. Clinicians should maintain a low threshold for ordering a biopsy to permit the histological exclusion of other diagnoses, particularly in individuals with known malignancy; this patient’s case emphasises the potential for diagnostic uncertainty even with advanced imaging and expert interpretation.

Reference: 1. Safavi K, Torian J, Timioh R, Jupiter D. A Systematic Review of Charcot Neuroarthropathy Misdiagnosis. Foot & Ankle Orthopaedics. 2022 Jan.