[Incomplete hemolytic uremic syndrome associated with partial factor H deficiency]

Area of Science:

• Nephrology
• Immunology
• Genetics

Background:

• Hemolytic uremic syndrome (HUS) is characterized by hemolytic anemia, thrombocytopenia, and renal failure.
• Typical HUS is often triggered by Shiga toxin-producing Escherichia coli, usually with a good renal prognosis.
• Atypical HUS (aHUS) has a less favorable prognosis and can result from genetic factors, including mutations affecting complement regulation.

Observation:

• This report details an unusual case of incomplete aHUS, lacking thrombocytopenia and uremia.
• The patient presented with hypocomplementemia, indicating a deficiency in complement regulatory proteins.
• Symptoms were precipitated by a preceding Campylobacter infection.

Findings:

• Partial deficiency of factor H was identified as the cause of hypocomplementemia.
• Genetic analysis revealed a heterozygous mutation (C846T) in the SCR4 domain of the factor H gene, resulting in a Pro240Leu amino acid substitution.
• This mutation is proposed to underlie the partial factor H deficiency and the observed aHUS phenotype.

Implications:

• This case expands the known spectrum of factor H mutations associated with aHUS.
• Understanding the genetic basis of aHUS is crucial for diagnosis and potential therapeutic strategies.
• The findings underscore the role of complement dysregulation in aHUS pathogenesis and the importance of identifying specific genetic defects.