Clinical features of HPHF:
(1) usually asymptomatic
(2) normal RBC count
(3) normal hemoglobin concentration
(4) normal MCV
Many affected patients are African or are of African descent.
Types of HPHF:
(1) deletional: deletion involving the delta and beta globin genes in chromosome 11, making it a form of thalassemia
(2) nondeletional: variable, including a single nucleotide substitution in the promoter region of a gamma globin gene
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Form of HPHF
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Percent Hemoglobin F
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heterozygous deletional
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20-40%
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homozygous deletional
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100%
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heterozygous nondeletional
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3 to 30%
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The distribution of increased hemoglobin F in red cells of a patient with heterozygous deletional HPHF is pancellular (homocellular, affects all cells). The nondeletional form may show a variable distribution (heterocellular) or a homocellular distribution.
Problems for a patient with HPHF
(1) Iron deficiency can result in findings that overlap with with delta/beta thalassemia.
(2) Detection of fetal red blood cells in an affected woman following delivery is difficult.
