What are the true statements about hemolytic-uremic syndrome (HUS)?

Hemolytic-Uremic Syndrome: Key Facts

Hemolytic-uremic syndrome (HUS) is characterized by non-immune hemolytic anemia, thrombocytopenia, and acute renal involvement, with infection by E. coli O157:H7 and exposure to Shiga toxin being established causes that can lead to progressive renal failure.

Accurate Statements About HUS

• HUS results from infection with E. coli O157:H7, which is one of the most common causes, particularly in children 1, 2
• HUS can develop from exposure to Shiga toxin, which is produced by certain strains of E. coli and is a key pathogenic mechanism 1, 3
• HUS may lead to progressive renal failure, with kidney damage being a hallmark feature of the condition 1, 4
• HUS is characterized by thrombocytopenia (low platelet count), not thrombocytosis (high platelet count) 1, 5
• HUS is not associated with hemophilia, as they are distinct conditions with different pathophysiological mechanisms 3, 4

Clinical Features and Diagnosis

• HUS is defined by the simultaneous occurrence of three key features:

  • Non-immune hemolytic anemia
  • Thrombocytopenia (low platelet count)
  • Acute renal failure 1, 3

• Laboratory findings typically include:

  • Schistocytes (fragmented red blood cells) on peripheral blood smear
  • Elevated lactate dehydrogenase (LDH)
  • Reduced haptoglobin
  • Negative direct and indirect Coombs tests 1, 6

• In pediatric patients, particularly newborns, HUS may be present even if one of the three main parameters (thrombocytopenia, anemia, or increased creatinine) is absent 1, 6

Types and Etiology

• Typical HUS (STEC-HUS) is associated with Shiga toxin-producing E. coli (STEC), particularly E. coli O157:H7 1, 7
• Atypical HUS (aHUS) is associated with complement dysregulation due to genetic mutations or autoantibodies 1, 4
• Secondary HUS can be triggered by medications, pregnancy, malignancies, infections, or organ transplantation 6, 1

Complications and Prognosis

• HUS can lead to progressive renal failure, with some patients requiring dialysis 1, 7
• Neurological complications may occur in approximately 33% of patients with STEC-HUS 7, 1
• Age under 3 years, leukocyte count over 20 × 10^9/L, and need for dialysis are predictive factors for poor renal outcome 7, 1

Treatment Approaches

• Treatment of typical HUS (STEC-HUS) is primarily supportive care 1, 3
• Complement inhibitors such as eculizumab are the standard of care for atypical HUS 1, 4
• Antibiotics should be avoided in cases of STEC O157 and other Shiga toxin 2-producing E. coli due to increased risk of HUS 2, 1

Important Clinical Considerations

• Early diagnosis and treatment are essential, as delays are associated with increased morbidity and mortality 6, 1
• A multidisciplinary team approach is recommended for managing HUS, especially aHUS 1, 6
• Patients receiving complement inhibitors must be vaccinated against meningococcal infection and receive antimicrobial prophylaxis 1, 6