Right medication can save patients with atypical hemolytic uremic syndrome from dialysis

Atypical hemolytic uremic syndrome (aHUS) is a rare disease that is difficult to diagnose, caused by abnormal activity of the “complement system,” one of the body's immune systems, leading to the destruction of red blood cells and kidney dysfunction, resulting in uremia.

“Atypical hemolytic uremic syndrome is a disease caused by the overactivation of the complement system, which is a congenital defense system that protects the body from bacteria and viruses,” said Professor Kim Chang-seong of the Department of Nephrology at Chonnam National University Hospital on the YouTube channel, “Angels' Spoon TV,” of the Korean Organization for Rare Diseases. “That leads to the destruction of red blood cells and kidney damage.”

Complement system activation can occur due to both genetic and environmental factors. Genetic factors involve genetic mutations that activate the complement system, while environmental factors include infections, medications, childbirth, and stress.

“In 40 percent of patients, genetic mutations are not identified. In such cases, the condition may arise due to various environmental factors that activate the complement system, including antibodies,” Professor Kim noted.

Both genetic and environmental factors can contribute to the development of atypical hemolytic uremic syndrome.

“In some cases, an underlying genetic condition is present, and later, environmental triggers can exacerbate genetic mutations, leading to complement activation and the onset of the disease,” Kim explained.

If there is a genetic mutation for atypical hemolytic uremic syndrome, it is inherited in an autosomal dominant pattern, meaning there is a 50 percent chance of inheritance. However, not everyone with the genetic mutation will develop the disease. “According to one study, the probability of developing symptoms is about 20 percent,” Kim emphasized, saying, “Not all patients with the genetic mutation will develop the disease.”

In aHUS, the condition does not end with kidney dysfunction. Professor Kim explained, “When the complement system is activated, very small microvessels are damaged, and along with this, various blood clots and platelets block the ends, leading to damage to multiple organs.”

Atypical hemolytic uremic syndrome affects microvessels, so all organs with microvessels can develop complications. “Typically, multiple organs, including the central nervous system, kidneys, digestive system, lungs, and muscles, can be affected. When complications occur in these organs, symptoms such as mental confusion, delirium, coma, pulmonary hemorrhage, digestive symptoms, and muscle damage may appear,” Kim noted.

If kidney function deteriorates, various symptoms may appear. Initially, hematuria and proteinuria may occur, and urine output may decrease. As kidney function worsens, symptoms such as edema, electrolyte imbalances, shortness of breath, and fatigue may be experienced, he added.

Atypical hemolytic uremic syndrome is a serious and difficult-to-treat condition with a poor prognosis, and the diagnosis itself is not straightforward.

Kim said, “It requires differentiation from other conditions, including thrombotic thrombocytopenic purpura, hemolytic uremic syndrome (hamburger disease), lupus, malignant infections, malignant hypertension, and vasculitis, making diagnosis challenging.”

The condition is suspected through blood tests and confirmed through differential diagnosis. “If a patient exhibits hemolytic anemia, reduced platelet counts, and elevated kidney function test results, atypical hemolytic uremic syndrome should be considered. Differential diagnosis may involve immunological tests, imaging studies, kidney biopsy, and genetic testing,” Kim explained.

After being diagnosed with aHUS, patients often become anxious due to its reputation as a rare disease with a poor prognosis. "The prognosis for aHUS is very poor. According to studies, about 50 percent of patients require dialysis within one month to one year,” Kim noted. “It is also a disease in which 50 percent of patients experience death within five years.”

However, the treatment environment for aHUS has undergone significant changes in recent years. “Without treatment, aHUS carries a risk of dialysis or death within one year, but recently, various treatments have become available,” he noted.

Professor Kim emphasized the importance of active treatment.

“When treatment is administered, patients show significantly better outcomes compared to the past, and many positive outcomes have been reported. Proper use of treatment can provide patients with the opportunity to live a normal life without dialysis,” Kim said.