Is Ferriscan - a Useful Tool for Diagnosing and Monitoring Tissue Iron Load after Acute Iron Intoxication?

Almost 16,000 iron exposures annually are reported in children less than six years of age in the United States. Deferoxamine is the iron-chelating agent of choice. Deferoxamine binds absorbed iron, and the iron-deferoxamine complex is excreted in the urine. Indications for treatment include shock, altered mental status, persistent GI symptoms, metabolic acidosis, pills visible on radiographs, serum iron level greater than 500 µg/dL, or estimated dose greater than 60 mg/kg of elemental iron. No clear end point of therapy is distinguished. Infusion of deferoxamine for 6-12 hours has been suggested for moderate toxicity. For severe toxicity, administer deferoxamine for 24 hours. Because these end points are arbitrary, observe the patient for the recurrence of toxicity 2-3 hours after the deferoxamine has been stopped. Complications of iron toxicity include the following: Infection with Yersinia enterocolitica, acute respiratory distress syndrome (ARDS) and fulminant hepatic failure, hepatic cirrhosis, pyloric or duodenal stenosis. Systemic toxicity is expected with an ingestion of 60 mg/kg. Ingestion of more than 250 mg/kg of elemental iron is potentially lethal.

Although a low serum ferritin is an accurate measure of iron deficiency, there is no accurate serum or plasma marker for acute body-iron overload. Serum iron concentration and transferrin saturation do not quantitatively reflect body iron. Stores and should therefore not be used as surrogate markers of tissue iron overload. Liver iron concentration provides the best measure of total body iron stores and is a validated predictor of the risks a particular patient faces from the complications of iron toxicity. Several imaging noninvasive techniques are available for measuring liver iron concentration (LIC) . There are two validated MRI methods for quantitating the liver iron burden: the FerriScan and T2 methods. The noninvasive R2-MRI technique (FerriScan) is highly sensitive and specific for estimating LIC and is approved by the Food and Drug Administration for routine clinical use. However, it was not used to diagnose and monitor LIC in cases of acute iron intoxication.

This 27 year old female nurse by profession self-referred to hematology clinic for evaluation of Iron overload after self injecting herself with 20 ampoules of IV iron Ferro sac (each ampoule containing 200 mg of iron, (4000 mg elemental iron, 60 mg/kg) . Her CBC on presentation showed Hb of 12.5 g/dl her baseline Hb 9 g/dl with serum iron of 28 (NR 9.0 - 30.4 umol/L) ,TIBC of 42 NR(45 - 80 umol/L ), ferritin 1001 (NR 24-336 mcg/l)

Her clinical exam was unremarkable. Her MRI showed severe iron overload. 9 mg /g dray tissue (NR 0.17-1.8) Patient received chelation with deferasirox at dose of 30 mg /kg for 6 months when her ferriscan showed almost normal LIC of 2 mg /g dry tissue.

This case report showed the value of ferriscan in diagnosing the degree of tissue iron overload and in monitoring chelation to a safe level of hepatic iron content.