Hemolytic uremic syndrome (HUS)

Overview

Hemolytic uremic syndrome (HUS) is a serious condition characterized by the inflammation and damage of small blood vessels, leading to blood clots that can harm the kidneys and other organs, potentially causing life-threatening kidney failure. While anyone can develop HUS, it primarily affects young children and is most commonly triggered by infections with certain strains of Escherichia coli (E. coli) bacteria. Other potential causes include different infections, certain medications, and conditions like pregnancy, cancer, or autoimmune diseases, as well as specific genetic mutations. Despite its severity, timely treatment often results in complete recovery, especially in young children.

Symptoms

Hemolytic uremic syndrome (HUS) is a complex condition that can vary in symptoms depending on its cause. When HUS is triggered by E. coli infection, initial symptoms often include:

• Gastrointestinal issues:
  • Diarrhea (potentially bloody)
  • Stomach pain, cramping, or bloating
  • Vomiting
  • Fever

As HUS progresses, it causes significant damage to blood vessels, leading to various severe symptoms due to anemia, blood clots, and kidney damage:

• Anemia and blood clots:
  • Pale skin
  • Fatigue
  • Easy bruising
  • Unusual bleeding (e.g., from the nose or mouth)
• Kidney damage:
  • Reduced urine output or blood in the urine
  • Swelling (edema) in legs, feet, ankles, and less commonly in the face, hands, or entire body
  • High blood pressure
  • Neurological symptoms: confusion, seizures, or stroke

Classic triad of HUS

The classic medical triad indicating HUS consists of:

• Microangiopathic hemolytic anemia: Damage to red blood cells.
• Thrombocytopenia: A steady decrease in platelet count.
• Acute kidney injury: Sudden impairment of kidney function.

Immediate medical consultation is advised if you or your child experiences:

• Bloody diarrhea
• Persistent diarrhea leading to symptoms such as:
• Reduced urination
• Swelling
• Bruising or unusual bleeding
• Extreme tiredness

Seek immediate medical attention if there is an absence of urination for 12 hours or more.

Causes

Hemolytic uremic syndrome (HUS) is a serious condition, most commonly triggered by infection with specific strains of E. coli bacteria, particularly in children under the age of 5. These strains produce a dangerous toxin known as Shiga toxin, making them referred to as Shiga toxin-producing E. coli (STEC).

While many of the hundreds of E. coli types are harmless, certain strains can lead to HUS. Beyond E. coli, other factors can cause this syndrome:

• Other infections: These can include infections from pneumococcal bacteria, the human immunodeficiency virus (HIV), or influenza viruses.
• Complications from other conditions: In rare cases, conditions such as pregnancy, autoimmune diseases, or cancer may lead to HUS.
• Certain medications: This category includes some cancer treatments and medications designed to prevent organ rejection in transplant recipients.

Additionally, an atypical form of HUS exists, which is inherited. Individuals with the gene for this form do not always develop the condition; however, factors such as infections, specific medications, or ongoing health issues can trigger HUS in those genetically predisposed.

Risk factors

Hemolytic uremic syndrome (HUS), caused by E. coli, can occur through various exposure routes including consuming contaminated meat, fruits, or vegetables, swimming in feces-contaminated pools or lakes, or having close contact with someone infected. The risk of developing HUS is particularly high among children under five, individuals with weakened immune systems, and those with specific genetic predispositions. E. coli infections often stem from eating undercooked meat, especially ground beef, or consuming unpasteurized milk, fruit juices, or contaminated raw produce. Additionally, E. coli can spread via the oral-fecal route, highlighting the importance of thorough hand washing after using the bathroom, changing diapers, or touching animals, as failing to do so can lead to the bacteria entering the system through consumed food or mouth contact.