Omar Adwan: Rare Genetic Disorders of Red Blood Cell Membrane Abnormalities
Omar Adwan, Medical Laboratory Technologist at Modawah lab center, shared a post on LinkedIn:
“Hereditary Stomatocytosis , Hereditary Xerocytosis and Hereditary Cryohydrocytosis
Hereditary Stomatocytosis , Hereditary Xerocytosis are rare genetic disorders inherited in an Autosomal dominant pattern, characterized by abnormalities in red blood cell sodium (Na⁺) and potassium (K⁺) permeability.
Hereditary Cryohydrocytosis is considered a subtype of hereditary stomatocytosis.
All 3 conditions cause hemolysis and anemia, with severity ranging from mild to severe.
The main clinical manifestations are the same as in other forms of hemolytic anemia.
1.Hereditary Stomatocytosis The hallmark feature water-laden erythrocytes.
Excessive influx of Na⁺ and water from the plasma, exceeding the loss of K⁺, leads to swollen red cells. Laboratory findings include:
- Increased mean corpuscular volume (high MCV)
- Low mean corpuscular hemoglobin concentration (low MCHC)
- Increased osmotic fragility
Blood smears show stomatocytes, sometimes mixed with spherocytes.
2.Hereditary Cryohydrocytosis
A milder variant of Hereditary Stomatocytosis.
The abnormality is a marked increase in Na⁺ permeability at temperatures below 20 °C, exceeding the ability of the cell to pump Na⁺ back out.
As a result:
- Red cells swell
- Partial hemolysis occurs when blood is stored in the refrigerator overnight
3.Hereditary Xerocytosis (also called dehydrated Hereditary Stomatocytosis)
This is the most common inherited red cell cation permeability disorder.
Key features
- A mild increase in K⁺ permeability causes progressive loss of K⁺ and water leading to red cell dehydration, stiffness, and hemolysis
- Red cells are macrocytic despite dehydration, with high MCHC and resistance to osmotic fragility
- Laboratory findings
- Hemoglobin (Hb) and hematocrit (Hct) are often within the normal range (compensated hemolysis)
- Blood smears appear mostly normal, with only a few target cells present
- HSt: overhydrated, low MCHC
- HX: dehydrated, high MCHC
- HC: cold-sensitive Na⁺ leak.”
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