Table 1.

Features of primary disorders of erythrocyte volume homeostasis

Overhydration syndromesIntermediate syndromesDehydration syndromes
ConditionOverhydrated hereditary stomatocytosis (hydrocytosis)Mild hereditary stomatocytosisCryohydrocytosisStomatocytic xerocytosisXerocytosis with high phosphatidyl-cholineXerocytosisFP
Hemolysis Severe Mild to moderate Mild to moderate Mild Mild to moderate Moderate None 
Anemia Severe Mild to moderate Mild to moderate to compensated None Moderate Mild to moderate None 
Blood smear Stomatocytes ± spherocytes Stomatocytes and/or spherocytes Stomatocytes ± spherocytes ± targets Stomatocytes Targets, echinocytes Targets, rare stomatocytes, or dessicytes Rare target or stomatocyte 
MCV (80-100 fL)* 110-150 95-130 90-105 91-98 100-110 90-110 82-104 
MCHC (32-36g/dL) 24-30 26-30 34-40 33-39 34-38 34-38 33-39 
Unincubated osmotic fragility Very increased Increased Variable Decreased Very decreased Decreased to very decreased Slightly decreased 
RBC Na+ (5-12 mEq/LRBC) 60-150 30-60 15-100 10-20 10-20 5-30 10-25 
RBC K+ (90-103 mEq/LRBC) 20-55 40-85 30-100 75-85 60-80 60-100 75-110 
RBC Na+ + K+ (95-110 mEq/LRBC) 110-170 115-145 70-130 87-103 75-90 70-110 85-110 
Phosphatidyl-choline content Normal ± Increased Normal Normal Increased Normal or increased Normal 
Cold autohemolysis No Unknown Yes No Unknown No No 
Pseudohyperkalemia Sometimes Unknown Yes Sometimes Sometimes Sometimes Yes 
Effect of splenectomy† Good Good Little or no effect Unknown Unknown Poor Not applicable 
Thromboembolism risk postsplenectomy Yes Unknown ? Yes Unknown Unknown Yes Unknown 
Inheritance Autosomal dominant Autosomal dominant Autosomal dominant Autosomal dominant Autosomal dominant Autosomal dominant, de novo Autosomal dominant 
Gene defects RHAG SLC4A1 SLC4A1, GLUT1 PIEZO1, unknown PIEZO1, unknown PIEZO1, KCNN4 ABCB6, PIEZO1 
Overhydration syndromesIntermediate syndromesDehydration syndromes
ConditionOverhydrated hereditary stomatocytosis (hydrocytosis)Mild hereditary stomatocytosisCryohydrocytosisStomatocytic xerocytosisXerocytosis with high phosphatidyl-cholineXerocytosisFP
Hemolysis Severe Mild to moderate Mild to moderate Mild Mild to moderate Moderate None 
Anemia Severe Mild to moderate Mild to moderate to compensated None Moderate Mild to moderate None 
Blood smear Stomatocytes ± spherocytes Stomatocytes and/or spherocytes Stomatocytes ± spherocytes ± targets Stomatocytes Targets, echinocytes Targets, rare stomatocytes, or dessicytes Rare target or stomatocyte 
MCV (80-100 fL)* 110-150 95-130 90-105 91-98 100-110 90-110 82-104 
MCHC (32-36g/dL) 24-30 26-30 34-40 33-39 34-38 34-38 33-39 
Unincubated osmotic fragility Very increased Increased Variable Decreased Very decreased Decreased to very decreased Slightly decreased 
RBC Na+ (5-12 mEq/LRBC) 60-150 30-60 15-100 10-20 10-20 5-30 10-25 
RBC K+ (90-103 mEq/LRBC) 20-55 40-85 30-100 75-85 60-80 60-100 75-110 
RBC Na+ + K+ (95-110 mEq/LRBC) 110-170 115-145 70-130 87-103 75-90 70-110 85-110 
Phosphatidyl-choline content Normal ± Increased Normal Normal Increased Normal or increased Normal 
Cold autohemolysis No Unknown Yes No Unknown No No 
Pseudohyperkalemia Sometimes Unknown Yes Sometimes Sometimes Sometimes Yes 
Effect of splenectomy† Good Good Little or no effect Unknown Unknown Poor Not applicable 
Thromboembolism risk postsplenectomy Yes Unknown ? Yes Unknown Unknown Yes Unknown 
Inheritance Autosomal dominant Autosomal dominant Autosomal dominant Autosomal dominant Autosomal dominant Autosomal dominant, de novo Autosomal dominant 
Gene defects RHAG SLC4A1 SLC4A1, GLUT1 PIEZO1, unknown PIEZO1, unknown PIEZO1, KCNN4 ABCB6, PIEZO1 

Modified in part from Lux122  with permission.

K+, potassium; LRBC, liter of red blood cells; MCV, mean corpuscular volume; Na+, sodium; PC, phosphatidylcholine; RBC, red blood cell.

*

Values in parentheses are the normal range.

†

Splenectomy is contraindicated in these disorders.

View Large