Hemosiderosis

Hemosiderosis
Other names	Haemosiderosis
Image of a kidney viewed under a microscope. The brown areas contain hemosiderin
Specialty	Hematology

Hemosiderosis is a form of iron overload disorder resulting in the accumulation of hemosiderin.

Types include:

• Transfusion hemosiderosis^[1]
• Idiopathic pulmonary hemosiderosis
• Transfusional diabetes^[2][3]

Organs affected:

• Hemosiderin deposition in the lungs is often seen after diffuse alveolar hemorrhage, which occurs in diseases such as Goodpasture's syndrome, granulomatosis with polyangiitis, and idiopathic pulmonary hemosiderosis. Mitral stenosis can also lead to pulmonary hemosiderosis.
• Hemosiderin collects throughout the body in hemochromatosis.
• Hemosiderin deposition in the liver is a common feature of hemochromatosis and is the cause of liver failure in the disease.
• Selective iron deposition in the beta cells of pancreatic islets leads to diabetes^[4][2] due to the distribution of transferrin receptor on the beta cells of islets^[3] and in the skin leads to hyperpigmentation.
• Hemosiderin deposition in the brain is seen after bleeds from any source, including chronic subdural hemorrhage, cerebral arteriovenous malformations, cavernous hemangiomata. Hemosiderin depositionon on the surface of the brain and spinal cord due to chronic bleeding in the subarachnoid space is known as superficial siderosis.
• Hemosiderin collects in the skin and is slowly removed after bruising; hemosiderin may remain in some conditions such as stasis dermatitis.
• Hemosiderin in the kidneys has been associated with marked hemolysis and a rare blood disorder called paroxysmal nocturnal hemoglobinuria.

Hemosiderin may deposit in diseases associated with iron overload. These diseases are typically diseases in which chronic blood loss requires frequent blood transfusions, such as sickle cell anemia and thalassemia, though beta thalassemia minor has been associated with hemosiderin deposits in the liver in those with non-alcoholic fatty liver disease independent of any transfusions.^[5][6]

Iron overload occurs when iron intake is increased over a sustained period of time due to regular transfusion of whole blood and red cells or because of increased absorption of iron through the gastrointestinal tract (GI).

Both these phenomena occur in thalassaemias, with blood transfusion therapy being the major cause of iron overload in thalassaemia major and increased GI absorption being more important in patients with intermedia thalassaemia who are not frequently transfused.

Each unit of blood contains about 200 mg iron. After 50 units have been transfused, or earlier in children, siderosis develops, with increased pigmentation of skin exposed to light and susceptibility to infection, reduced growth and delayed sexual development and puberty⁽²⁴⁾. The recommended red cell transfusion scheme for patients with β-thalassaemia amounts to 116–232 mg iron per Kg weight on an annual basis (0.32-0.64 mg/Kg/day).

The human body lacks a mechanism to excrete excess iron. Iron accumulation is toxic to many tissues, causing heart failure, cirrhosis, liver cancer, growth retardation and endocrine abnormalities. In the absence of regular iron chelation therapy, the iron loading rates vary. Monitoring of transfusion iron overload is essential for effective and safe iron chelation tailored to the individual's specific needs.

Serum ferritin (SF) measured at least every 3 months (the currently accepted target value is between 500 and 1000 mg/L) should also be evaluated along with the liver iron concentration (LIC) assessed using a validated and standardized MRI technique and myocardial iron as measured by MRI-based methods with specific software T2*.

For monitoring of transfusion iron overload, other organ function and iron-mediated damage, surveillance of the patient for diabetes, hypothyroidism, hypoparathyroidism and hypogonadotropic hypogonadism is recommended.