hereditary stomatocytosis (cryohydrocytosis)

Pathology

• erythrocyte anomaly associated with hemolytic anemia
• increased Na+/K+-permeability, thus disorder of cell volume control
• associated with stomatin deficiency

Genetics

• autosomal dominant
• hereditary stomatocytosis associated with
  • mutations in the band 3 chloride-bicarbonate exchanger AE1/SLC4A1
  • mutations in the erythroid ammonia channel Rh-associated glycoprotein (RHAG)
  • mutations in erythroid glucose transporter SLC2A1/GLUT1

Clinical manifestations

• many patients present with neonatal hemolytic anemia
• others are asymptomatic throughout life

Laboratory

• complete blood count
  • anemia
  • MCV as high as 110-150 fL hydrocytes
  • Coulter counter overestimates size of xerocytes
  • WBC count & platelet count generally normal
• reticulocyte count is elevated with hemolysis
• peripheral blood smear
  • 5-50% stomatocytes; < 3% is normal
• osmotic fragility test
  • overhydrated stomatocytosis are osmotically fragile
  • dehydrated stomatocytosis are resistant to osmotic lysis

Complications

• aplastic crises associated with parvovirus infection
• iron overload is common
  • adults may be diagnosed with hemochromatosis
• complications of hemolysis
  • cholilithiasis

Management

• folic acid for significant hemolysis
• chelation with deferoxamine for iron overload

More general terms

• stomatocytosis; hydrocytosis; xerocytosis
• genetic disease of the blood/bone marrow