Factor H is a protein in the complement system that regulates C3 activation. Deficiency of Factor H can result recurrent episodes of hemolytic uremic syndrome (HUS) or membranoproliferative glomerulonephritis.
Clinical features:
(1) The patient has recurrent episodes of hemolytic uremic syndrome or membranoproliferative glomerulonephritis.
(2) The patient develops a secondary deficiency in C3.
(3) Levels of Factor H are low in a homozygous patient. Heterozygous deficiencies may be missed.
(4) Most cases that have been detected have been homozygous, although heterozygous cases have been reported. A homozygous patients may have affected siblings or relatives.
Differential diagnosis: SLE or other autoimmune disorders with consumption of complement
Factor H deficiency should be considered in any patient with recurrent or familial HUS or membranoproliferative glomerulonephritis.
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