Hemosiderosis and hemochromatosis

Mixed dystrophies and complex proteins

To understand the mechanisms of development of hemosiderosis and hemochromatosis, it is necessary to examine the concept of mixed dystrophies. These are pathological processes characterized by quantitative and qualitative structural changes in tissues. Their main distinguishing feature is the totality of the lesion. Metabolic disorders do not occur in isolation, but simultaneously in the three most critical components of any organ:

1. In the parenchyma (specific functional cells).
2. In the stroma (connective tissue supporting framework).
3. In the vessel walls (structures ensuring blood supply).

The essence of this pathological process boils down to the fact that metabolic products of complex proteins, or proteids, begin to accumulate in excess both inside the cells themselves and in the surrounding intercellular substance. In pathological anatomy, three main groups of such complex proteins are distinguished: chromoproteins, nucleoproteins, and lipoproteins. The diseases we are discussing are directly related to the metabolic disturbance of the first group—pigmented proteins.

Disorders of pigment metabolism

Pigments are special colored substances whose accumulation visually and structurally alters the affected tissues. Disorders of pigment metabolism are always associated with the excessive accumulation of these compounds. By origin, all pigments are divided into two broad categories: exogenous (entering the body from the external environment) and endogenous (synthesized within the body itself).

The most extensive and clinically significant group of endogenous pigments is hemoglobinogenic pigments. As the name implies, all of them are various derivatives of hemoglobin. Hemoglobin itself is a high-molecular-weight chromoprotein. Its molecule has a complex structure and consists of two inseparable components: an iron-containing part (called heme) and a protein base (called globin). It is precisely the breakdown and transformation of this molecule that give rise to all other pigments in this group.

Classification of hemoglobinogenic pigments

In pathological anatomy, hemoglobin derivatives are strictly classified according to one key biochemical feature: the presence or absence of iron molecules in their structure.

Iron-containing pigments (Fe+):

• Hemoglobin (basic chromoprotein);
• Ferritin;
• Hemosiderin (pigment whose excess causes haemosiderosis);
• Hematins.

Non-iron-containing pigments (Fe-):

• Bilirubin;
• Hematoidin;
• Porphyrins.

It is extremely important to understand the difference between the physiological and pathological presence of these substances in tissues. Normally, in a healthy body, hemoglobin, ferritin, hemosiderin, and bilirubin can always be detected. However, the appearance of pigments such as hematoidin, hematins, and porphyrins is an absolute marker of pathology—they are not found in healthy tissues.

Hemochromatosis as an extreme degree of disorder

Hemochromatosis (haemochromatosis) represents an extremely severe form of chromoprotein metabolism disorder. According to strict pathomorphological criteria, this pathology is diagnosed and occurs when the total iron content in the human body exceeds the critical threshold of 15 grams.

Such massive iron overload leads to massive quantitative and qualitative structural changes. The excess of iron-containing pigments impregnates the parenchyma, stroma, and vessels, fully fitting into the classical morphological picture of severe mixed dystrophy.

Class and exam questions

What else to study on this topic

• Morphological differences of quantitative and qualitative structural changes in dystrophies.
• Mechanisms of accumulation of complex protein metabolic products in the intercellular substance.
• Differential diagnosis of exogenous and endogenous pigment metabolism disorders.
• Pathogenesis of hematoidin, hematins, and porphyrins formation in various diseases.
• The role of nucleoproteins and lipoproteins in the development of other types of mixed dystrophies.

Other topics in the section "Morphology of Metabolic Disorders — Dystrophies"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.