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Diagnosis: Hemolytic Uremic Syndrome

Hemolytic-uremic syndrome (HUS) is a clinical syndrome characterized by renal failure, nonimmune coombs-negative thrombotic microangiopathy, hemolytic anemia and thrombocytopenia.

HUS is classified into 2 main categories, depending on whether it is associated with Shiga-like toxin or not. Typical HUS is largely a disease of children younger than 2-3 years, it is associated to Shiga-like toxin and often results in diarrhea (denoted D+HUS). Acute renal failure occurs in 55-70% of patients, but they have a favorable prognosis, and as many as 70-85% of patients recover renal function. Atypical HUS is not asociated to Shiga-like toxina or diarrhea (denoted D-HUS) and is less common than D+HUS and accounts for 5-10% of all cases. Overall, patients with D-HUS have a poor outcome, and as many as 50% may progress to end-stage renal disease or irreversible brain damage. The familial form is associated with genetic abnormalities of the complement regulatory proteins.

In sporadic D-HUS various triggers have been identified: nonenteric infections, viruses, drugs, malignancies, transplantation, pregnancy, and other underlying medical conditions (eg, antiphospholipid syndrome, systemic lupus erythematosus, among others). Familial D-HUS accounts for <3% of all cases of HUS. Both autosomal dominant and autosomal recessive forms of inheritance are observed. There are genetic abnormalities in the complement regulatory proteins: C3, factor H, factor B, factor I, and CD46 (membrane cofactor protein, MCP) (Parmar MS. Hemolytic uremic syndrome. In eMedicine.Medscape.com [Link]).

In the present case, the biopsy showed thrombotic microangiopathy. The diagnosis of HUS was made correlating biopsy findings with clinical and laboratory. Fortunately, the child recovered completely within 2 weeks.

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