Hydroxyapatite deposition disease, an overlooked differential diagnosis in the emergency department: a case series and review of literature.

Hydroxyapatite crystal deposition disease (HADD) poses diagnostic challenges in the emergency department (ED) as it may clinically present similarly to infection and other musculoskeletal conditions. Misdiagnosis often leads to unnecessary treatments and resource over-utilization. This review article provides an overview of HADD in seven patients who presented to the ED secondary to an acute presentation of this disease process. HADD is a prevalent pathology, which commonly involves the shoulder, followed by the hip, elbow, wrist, and knee. Predisposing risk factors, such as diabetes and certain genetic factors, have also been identified. Clinical history and imaging, particularly radiographs, play a vital role in diagnosing HADD, with characteristic calcification patterns observed in different stages of the disease. Conservative nonsurgical therapy is the mainstay of treatment, providing effective symptom relief in over 90% of cases. By recognizing HADD as a crucial differential diagnosis for patients with acute or chronic pain, healthcare resource utilization can be optimized, leading to improved patient care in the ED.