Normal and pathological hemolysis

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Definition :

Physiological hemolysis is the destruction of the GR after a lifetime of 120 j, it is offset immediately by the MO, no clinical impact or biological.

– It must be differentiated from pathological hyper hemolysis or hemolysis associated with changing 3 vital factors for GR :

  • Erythrocyte membrane.
  • Energy metabolism : enzymes.
  • The hemoglobin content.

The HAEMOLYSIS PHYSIOLOGICAL :

1/ Demonstration of the physiological hemolysis :

By radioactive labeling the GR or by chromium 51 or marked glycine and follows the GR :

  • average life duration of a GR is 120J.
  • each GR destroyed is replaced immediately (every day, there is a renewal 1/120 mass erythrocyte).

2/ Causes and mechanisms of hemolysis :

A- Features GR :

The absence of core means 3 notions :

  • Inability of the protein system (there is no DNA or RNA)
  • So a limited and predetermined enzyme and energy stock.
  • The progressive wear and loss of non-renewable components.

The GR energy metabolism has the role of :

  • Maintain a powerful activity NADH NADPH-reducing system.

Indeed this system is necessary for the Hb is protected against oxidation of its constituents (do you globine).

In this system NADH is provided by the main route of glycolysis and NADPH is provided exclusively by the accessory pathway.

  • Produce ATP : This is necessary for the proper functioning of the Na + / K + and therefore the osmotic balance of the G R (fight against overhydration).

It is provided by glycolysis largely through the primary route.

B- GR Characteristics aged :

GR constituents know more alterations :

  • Trouble ion exchanges : tdu flow of Na + into the cell and J,the concentration of intracellular K +.
  • membrane alterations
  • J,ATP levels, from 2-3 DPG which lowers the affinity for PHb 02.

The pre-condition haemolytic : impaired blood cell plasticity, with |the rigidity, sphérocytose, microcytose.

So the GR will be trapped in capillaries and phagocytosed by macrophages of the liver and MO (reticuloendothelial system).

Become GR constituents :

– the stroma : decomposed in the cytoplasm of macrophages.
– L’ Hb : each constituent lane following :

  • La depth : degraded AA joining the global pool of AA.
  • The iron : attached to the ferritin and reused for the biosynthesis of Hb.
CATABOLISM OF RED BLOOD CELLS

The hyperhemolysis = HAEMOLYSIS DISEASE :

It is early and exaggerated destruction of circulating GR under the effect of a hemolytic process that can be intrinsic (hemolysis corpuscular) or extrinsic (Hemolysis extra-corpuscular).

This process can be congenital or acquired, it always assigns one of the vital components of the GR : membrane, enzyme, Hb.

mechanisms :

A- Hemolysis corpuscular origin :

1- malformation globular :

  • Sickle Cell (sickle) characterized by the presence of Hb.
  • Thalassémies (microcytes) : a or p thalassemia

2- membrane abnormalities :

  • Micro-spherocytosis (|permeability to Na + and water)
  • hereditary elliptocytosis.
  • Stomatocytose.
  • Ancanthocytose (disturbance of the membrane lipids trade)

3- Erythro-enzymopathies birth :

  • G6PD deficit
  • Pyruvate kinase deficiency : ATP regeneration default.

4- Maladie de Micheli Marchiafava :

B- Hemolysis extra-corpuscular :

1- immunological causes :

Where fixing of a AC on the GR resulting in complement activation with hemolysis

Intra-Vx is destroyed by phagocytes GR various organs (foie, rate).

  • iso-immune hemolysis : after recent transfusion (exp : AC anti-Rh) or during the perinatal hemolytic disease.
  • hemolysis autoimmune.
  • hemolysis immuno-allergic : due to attachment of an Ag-Ab complex of the GR.

2- toxic causes : Lead, venoms of snakes and copper.

3- infectious causes :

  • bacterial : septicemia Clostridium perfringens or Staphylococcus.
  • Parasitic : plasmodium.
  • viral : viral hepatitis.

4- mechanical causes : micro-angiopathies, les valves intracardiaques, CHECK.

Exploration of hyper-hemolysis :

A- Asserting hyper-hemolysis :

1- indirect criteria :

  • amnesic : family ATCD, personal (heart valves), infectious context, transfusion, drug, toxic.
  • clinics : Triad : pallor, icterus, SPM (inconstant)
  • biological :

* Normochromic normocytic anemia + ↑ reticulocyte rates.
* hyper-catabolism Signs of Hb : ↑ BNC,↑ serum iron,↑ Stercobilinogène,↑ urobilin, ↓ haptoglobine.

2- direct criteria : study of the lifetime of the labeled GR chromium 51.

B- Determining the seat of hyper-hemolysis :

1- intravascular hemolysis :

  • ↑ hemoglobin, and hemoglobinuria and decrease in haptoglobin rate α.

2- hemolysis extra- vascular (tissue) :

  • Highlighted by the marked GR cytochrome 51.

C- Search aetiology :

1- Search corpuscular abnormalities :

  • Study constant corpuscular : blood count, hematocrit, Hb.
  • Blood smear : Research spherocytes, ovalocytes, acanthocytes, sickle cell, Heinz bodies (G6PD deficit, Hb instable).
  • Study of globular resistance to hypotonic solutions
  • Determination of globular enzymes : pyruvate kinase, G6PD.
  • Analysis of T Hb : Hb electrophoresis.

2- Search plasma factors :

  • globular tests : direct Coombs test to look for Ac attached to the GR.
  • serum tests : exp : test de Coombs indirect
  • Other : Blood cultures, tick drop…

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