CASE REPORTS Hypophosphatemic Rickets Presenting as Recurring Pedal Stress Fractures in a Middle-Aged Woman Randy Linde, MD,1 Amol Saxena, DPM,2 and David Feldman, MD3 Stress fractures frequently occur from overtraining. When stress fractures recur, underlying metabolic abnormalities should be ruled out. We report a middle-aged woman in whom such an evaluation demonstrated previously undiagnosed hypophosphatemic rickets after she presented with recurring stress fractures in her feet. Treatment with phosphate and calcitriol was associated with clinical improvement that would likely not have occurred without this intervention. Any patient with recurring stress fractures should be evaluated with several screening laboratory tests, metabolic bone x-reys, and a measurement of bone mineral density. (The Journal of Foot & Ankle Surgery 40(2):101-104, 2001) Key words: hypophosphatemia, metatarsals, rickets, stress fracture Stress fractures of the foot are relatively common, particularly in athletes. Although most of these injuries are rather self-limiting, multiple recurrences are uncommon. The cause of the recurrent fractures may be either mechanical or metabolic in nature and may be obscure. Mechanical etiologies can be related to a biomechanical imbalance, training errors, or both. A metabolic etiology should be considered in any patient with recurring stress fractures (1). Harper reported on a patient who presented with multiple recurrent metatarsal fractures and was later shown to have defective mineralization from hypophosphatasia, a defi- ciency of alkaline phosphatase (2). While other patients with this disorder have had metatarsal involvement (3, 4), we are unable to find a previous report of rickets having been diagnosed in an adult on this basis. We describe a middle-aged woman who presented with multiple stress fractures in her feet, low levels of serum phosphorus, and From the I Department of Endocrinology and 2Department of Sports Medicine, Palo Alto Medical Foundation, Palo Alto, CA and 'Division of Endocrinology, Stanford University Medical School, Stanford, CA. Address correspondence to: Amol Saxena, DPM, Department of Sports Medicine, Palo Alto Medical Foundation, Palo Alto, CA 94301. E- mail:Heysax@aol.com. Received for publication February 12, 1999; accepted in revised form for publication November 19,2000. The Journal of foot & Ankle Surgery 1067-251610l/4002-0101$4.0010 Copyright © 2001 by the American College of Foot and Ankle Surgeons comparatively high urinary phosphorus excretion consis- tent with hypophosphatemic rickets. When mild, this condi- tion may escape detection in childhood only to present later in life with skeletal disease (5). Case Study A 51-year-old woman was referred for a second opinion regarding recurring stress fractures in her right foot. Over the past 3 years, she had suffered two stress fractures of the right first metatarsal and three stress fractures in the right third metatarsal. The patient walked 20-25 miles per week and exercised in a Jazzercise class three to four times each week on a concrete surface covered by carpet. As a child, she had mildly bowed legs, confirmed by a photograph that the patient brought in with her. As an adult, she had chronic pain from osteoarthritis of weightbearing joints. She had undergone arthroscopic shoulder surgery as well as four knee operations, including cartilage removal, loose body removal, arthroscopy, and a lateral closing wedge tibial osteotomy. She also had a hysterectomy at age 48. She drank 16 ounces of milk and took a multivitamin daily, with a 600-mg calcium carbonate tablet several times per week. She was taking 0.625 mg of conjugated estrogen on a daily basis. No family member was recognized as having metabolic bone disease. VOLUME 40, NUMBER 2, MARCH/APRIL 2001 101