The adult human body contains about 4 g of
iron. About 1-2 mg of
iron is absorbed every day, and in healthy individuals, the same amount is excreted. We describe a patient who presents with severe
iron deficiency anemia with
hemoglobin levels below 6 g/dL and
ferritin levels below 30 ng/mL. Although red blood cell concentrates and intravenous
iron have been substituted every month for years, body
iron stores remain depleted. Diagnostics have included several esophago-gastro-duodenoscopies, colonoscopies, MRI of the liver, repetitive bone marrow biopsies, psychological analysis, application of radioactive
iron to determine intact erythropoiesis, and measurement of
iron excretion in urine and feces. Typically, gastrointestinal
bleeding is a major cause of
iron loss. Surprisingly, intestinal
iron excretion in stool in the patient was repetitively increased, without gastrointestinal
bleeding. Furthermore, whole exome sequencing was performed in the patient and additional family members to identify potential causative genetic variants that may cause intestinal
iron loss. Under different inheritance models, several rare mutations were identified, two of which (in CISD1 and KRI1) are likely to be functionally relevant. Intestinal
iron loss in the current form has not yet been described and is, with high probability, the cause of the severe
iron deficiency anemia in this patient.