Bilateral Hip Arthritis in a Young Patient with Anorexia Nervosa

Introduction: Anorexia nervosa (AN) is a disorder of low body weight, fear of gaining weight and a distorted body image. The malnutrition in AN leads to various medical complications and accounts for 50% of the deaths in this disease. We present a case of bilateral hip arthritis in a young patient with AN and link it to her eating disorder.

Case: A 37 female with a long history of AN presented to a rheumatologist with pain in the hands and hips. Hip joint range of motion was restricted. Imaging was negative for osteonecrosis. A bone scan showed increased uptake in both hips. A sclerotic bone matrix was noted on computed tomography. A metabolic bone disease was suspected. Hormonal testing was normal. A bone biopsy demonstrated thickened and unorganized trabeculae. Patient was seen by an orthopaedist where arthritis of both hip joints was noted clinically and on radiography. Lidocaine test was positive; aspiration culture was negative. Patient underwent staged bilateral hip replacement with non-cemented components, from which she recovered well. Due to the patient`s psychiatric disorder and altered nutritional status, imagining findings, early hip arthritis with no structural or rheumatic disease and a normal metabolic profile, systemic fluorosis was suspected. Fluoride levels in the patient`s femoral head were 2650 mg/kg, while those of a normal control were 3300 mg/kg. On repeat history, the patient admitted to daily ingestion of a tube of toothpaste for the last 7 years. Thus, the diagnosis of systemic fluorosis, as a cause of arthritis, was confirmed.

Discussion: Osteoarthritis in the young is usually associated with mechanical (post-traumatic, developmental) abnormalities or rheumatic diseases. We presented a rare case where arthritis was caused by a self-inflicted metabolic disorder. We suggest a multidisciplinary approach when treating patients with uncommon presentations, especially when a metabolic bone disease is suspected.