R.G. Wiseman Pinto
This article presents a case of hemosiderosis in a patient with thalassemia who was receiving repeated blood transfusions. Pathogenesis, clinical features and histopathological diagnosis is presented along with a review of literature.
Hemosiderosis means the presence of demonstrable iron in tissues irrespective of the cause. Most of the iron is deposited in parenchymal organs like liver and pancreas. Iron overload disorders can be categorized into primary and secondary types. The term primary iron overload disorders include forms of hereditary hemochromatosis in which genetic mutations alter iron homeostasis in the gastrointestinal tract. Secondary disorders are mainly acquired conditions in which the excess iron is derived from exogenous sources, abnormal erythrocyte destruction, or an underlying liver disease leading to changes in iron absorption and distribution.
A 12-year old boy, a known case of thalassemia major, with a history of receiving multiple blood transfusions was declared ‘dead on arrival’ (DOA) when brought to Goa Medical College. A medicolegal autopsy was conducted and tissues from various organs were sent for histopathological examination. Microscopic examination of the tissues sent showed a diffuse deposition of golden-yellow pigment both intracellularly as well as extracellularly. The pigment appeared blue on Prussian blue staining and was hence confirmed to be hemosiderin. Thus, the final histopathological diagnosis of hemosiderosis was made.
Hemosiderosis is characterized by excessive accumulation of iron in tissues. The main forms of tissue iron are ferritin, hemosiderin and haem, of which the stainable iron is mainly hemosiderin. It mainly affects parenchymal organs like liver and pancreas followed by heart, joints and endocrine organs. Iron overload can be categorized into primary (hereditary) hemochromatosis and secondary hemochromatosis (hemosiderosis). Normally, the total body content of iron is tightly controlled by intestinal absorption of iron with the help of regulatory proteins mainly hepcidin, human hemochromatosis protein(HFE), hemojuvelin, transferrin receptor and ferroportin.
In hereditary hemochromatosis, the regulation of intestinal absorption of dietary iron is abnormal, causing a net iron accumulation. It includes a group of autosomal recessive disorders caused by mutations of the HFE gene which encodes HFE, transferrin receptor 2, hepcidin or hemojuvelin.
Secondary hemochromatosis or hemosiderosis can be caused due to:
- Parenteral iron overload following repeated transfusions, long term hemodialysis, and repeated iron dextran injections.
- Ineffective erythropoiesis with increased erythroid activity, for example, in β thalassemia major.
- Increased oral iron intake, e.g. African Bantu siderosis.
- Congenital atransferrinemia.
- Chronic liver disease.
Excessive iron is toxic to host tissues by the following mechanisms:
- Lipid peroxidation via iron catalyzed free radical reactions.
- Stimulation of collagen formation by activation of hepatic stellate cells.
- Interaction of reactive oxygen species and of iron itself with DNA leads to lethal cell injury or predisposition to hepatocellular carcinoma.
Grossly, the liver is slightly larger than normal and has a chocolate brown appearance in early stages of accumulation. In later stages, it becomes dark brown to nearly black as a result of massive iron accumulation. Iron is not demonstrable in the normal liver using standard histochemical stains. Stainable iron is abnormal. Based on the distribution of stainable iron in the liver, the cause of siderosis can be suggested. Siderosis is usually demonstrated by Perl’s stain(using acid ferrocyanide) which gives the Prussian blue reaction with ferric compounds like ferritin & hemosiderin (Figure 1).
Figure 1. Section of liver showing diffuse deposition of hemosiderin pigment demonstrating positive Prussian blue reaction. (Perl’s stain x 100)
In most of the primary iron overload disorders, the excess iron is mainly hepatocellular. In thalassemia, iron is seen in both hepatocytes and macrophages. Exogenous iron overload initially only affects the Kupffer cells and portal tract macrophages. But once the threshold for macrophage iron storage is reached, iron can be demonstrated in the periportal hepatocytes as well. Inflammation is characteristically absent. Fibrous septa develop slowly, leading to micronodular pattern of cirrhosis (Figure 2).
Figure 2. Section of liver showing diffuse deposition of brownish hemosiderin pigment. (Hematoxylin and Eosin x 100)
Normal iron content of liver tissue is <1,000 μg/g dry weight of liver. Adults with hereditary hemochromatosis have >10,000 μg of iron/g dry weight of liver. More than 22,000 μg of iron/g dry weight of liver is associated with development of fibrosis & cirrhosis.
Hemosiderin is found in both acinar as well as islet cells and interstitial stroma. Varying degrees of interstitial fibrosis and parenchymal atrophy are observed (Figure 3).
Figure 3. Section from pancreas showing deposition of hemosiderin pigment. (Hematoxylin and Eosin x 100)
The heart appears enlarged and shows a brownish coloration because of accumulation of hemosiderin granules within the myocardial fibres. A delicate pattern of interstitial fibrosis may be seen (Figures 4 and 5).
Figure 4. Section from the heart showing deposition of hemosiderin pigment and interstitial fibrosis. (Hematoxylin and Eosin x 100)
Figure 5. Section from the heart demonstrating brown hemosiderin granules within myocardial fibres. (Hematoxylin and Eosin x 400)
Skin pigmentation is partially attributable to hemosiderin deposition in dermal macrophages and fibroblasts. Most of the pigmentation results from increased epidermal melanin production. The combination of these pigments imparts a characteristic slate-gray color to the skin.
Hemosiderin deposition in joint synovial lining leads to acute synovitis. Excessive deposition of calcium pyrophosphate damages the articular cartilage leading to polyarthritis (pseudogout).
Testes may be small & atrophic secondary to derangement in hypothalamic-pituitary axis resulting in reduced gonadotropin and testosterone levels.
Majority of the cases are asymptomatic and detected during screening. The most common symptom is arthralgia, and most commonly involves the metacarpophalangeal (MCP) joint. Other symptoms include fatigue, lethargy, weight loss, abdominal pain, amenorrhea in females, and loss of libido in males. Other findings include abnormal skin pigmentation, hepatomegaly, diabetes mellitus and cardiomyopathy.
The most common laboratory abnormalities are elevation of serum iron and percentage saturation of transferrin. Serum ferritin levels reflect the degree of iron overload.
Liver biopsy should be evaluated for the distribution of stainable iron among various cell types, grade of siderosis, presence of related tissue damage (fibrosis, cirrhosis, necrosis or hepatocellular carcinoma) and coexisting liver disease of other etiology. The tissue iron concentration in the liver can be determined by examining the tissue obtained for histology or fine needle aspiration biopsy or paraffin blocks once histological examination is complete.
Hepatic iron index= tissue iron in μmol/g dry weight of liver ÷ age of the patient at the time of biopsy (in years).
It is ≥ 1.9 in classic H F E – related hemochromatosis and <1.9 in heterozygotes and siderosis from other causes.
Bone marrow examination may show increased iron stores, demonstrable by Prussian blue reaction.
Computerized image analysis is another approach to measure the tissue iron deposition and correlates well with biochemical assay.
Multicolour multiplex HFE assay classifies all possible genotypes for HFE (C282Y and H63D) mutations.
HEMOSIDEROSIS SECONDARY TO THALASSEMIA:
In thalassemia major, there is apoptosis of erythroid precursors, failure of erythroid maturation and secondary expansion of erythropoiesis. Iron overload occurs due to increased intestinal iron absorption, hemolysis and repeated blood transfusions.
Transfusion siderosis is the biggest killer in thalassemia.
- 1000 children are born with thalassemia major each year in India.
- Iron deposition in parenchymal tissues begins within one year of starting regular transfusions.
- Each unit of packed cells contains 200 milligrams of iron. Hence, a patient who receives 25 units/year accumulates 5 grams of iron/year in the absence of chelation therapy. In addition, there is an increased absorption of intestinal iron in these patients.
- Cardiac siderosis is a leading cause of death in thalassemia major (71%).
- In India, up to 42% thalassemics have glucose intolerance due to transfusion hemosiderosis.
- Kumar V, Abbas AK, Aster JC. Robbins and Cotran Pathologic Basis of Disease. 8th ed. Philadelphia: Elsevier, p. 821-881. 2010
- Lethowitch JH. Scheuer’s liver biopsy interpretation. 8th ed. Philadelphia: Elsevier. p.282-291, 2010
- Geller SA, Petrovic LM. Biopsy interpretation of liver. 2nd ed. Philadelphia: Wolters Kluwer Health, p. 209-218, 2009.
- Prabhu R, et al. Iron overload in beta thalassemia: a review. J Biosci Tech. 2009: 1(1);20-31