High-Mileage Running-Induced Heel Strike Anemia in a 46-Year-Old Female.

Foot-strike hemolysis is an underrecognized cause of iron-deficiency anemia in endurance athletes, resulting from repetitive mechanical destruction of erythrocytes during prolonged running. While often subclinical, extreme training volumes may overwhelm compensatory mechanisms and lead to clinically significant anemia that is frequently misattributed to nutritional deficiency or gastrointestinal blood loss. We present a 46-year-old female with mild intellectual disability secondary to traumatic brain injury (TBI) who presented with progressive fatigue and left hip pain. Imaging demonstrated a left femoral neck stress fracture, and laboratory evaluation revealed severe iron-deficiency anemia with a hemoglobin of 8.2 g/dL, elevated total iron-binding capacity, and reduced serum iron, representing a marked decline from pre-injury baseline values. Objective activity monitoring revealed previously unrecognized compulsive endurance exercise behavior, with the patient running 27-32 miles daily for approximately 700 consecutive days. Based on the available clinical data and the patient's presentation, foot-strike hemolysis-associated iron-deficiency anemia was considered the most likely diagnosis. Temporary cessation of running and mechanical off-loading resulted in complete normalization of hematologic indices within eight weeks, further supporting the presumptive diagnosis. This case highlights the importance of considering mechanical causes of anemia in endurance athletes and demonstrates the value of objective activity assessment, particularly in patients with impaired insight, to prevent delayed diagnosis and unnecessary investigations and interventions.