aHUS disease in adolescence linked to permanent kidney function loss in study

More severe kidney dysfunction seen compared with infantile-onset aHUS

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by Andrea Lobo |

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Atypical hemolytic uremic syndrome (aHUS) starting during adolescence is associated with more permanent and severe kidney dysfunction when compared with infantile-onset disease, a study from Turkey reported.

“In the long term, adolescents may have significant permanent loss of [kidney] functions and higher [end-stage kidney disease] rates,” the researchers wrote.

“Most prominently,” according to the researchers, the rate of remission for adolescence-onset aHUS patients was found to be significantly lower than that seen in individuals with infantile-onset disease.

Thus, the team wrote, “adolescence-onset aHUS should be timely and meticulously managed during the acute phase and should be closely followed up in the long term.”

Their study, “Adolescence-onset atypical hemolytic uremic syndrome: is it different from infant-onset?” was published in the journal Clinical and Experimental Nephrology.

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Comparing adolescence-onset aHUS with infantile-onset disease

aHUS is a type of thrombotic microangiopathy, a group of diseases characterized by red blood cell destruction known as hemolytic anemia, low levels of platelets, and the formation of blood clots inside small blood vessels, which can damage several organs, most commonly the kidneys.

The disease can affect both children and adults of any age. But the researchers noted their “clinical observations as well as the available limited data in the literature suggest that the characteristics of aHUS triggered during adolescence … may differ from both infantile and adult-onset aHUS.”

Particularly, when the disease starts during adolescence, patients may not show the three hallmark symptoms of aHUS: hemolytic anemia, low platelet levels, and acute kidney injury. This may lead to delays in diagnosis and treatment.

To better understand the specific characteristics of adolescence-onset disease, the researchers analyzed data from patients who were diagnosed with aHUS between the ages of 10 and 18. Patient data were obtained from the Turkish Pediatric aHUS registry.

A total of 28 patients, 21 girls and seven boys, with a mean age at the time of aHUS diagnosis of 12.8 years, were included in the study. Data from 53 infantile-onset patients also were analyzed for comparison.

“In the present study, we showed, by analyzing Turkish Pediatric aHUS registry data, that adolescence-onset aHUS patients account for 18.5% of the pediatric aHUS cases,” the researchers wrote. They noted that the prevalence had been “estimated to comprise 10% of pediatric aHUS patients,” which was lower than what their study found.

In almost half of adolescence-onset patients, the disease affected organs other than the kidneys — mainly the central nervous system, comprising the brain and spinal cord.

As a first line of treatment, 20 patients (71.4%) received plasma-based therapy. Of these, 15 also were treated with Soliris (eculizumab) due to insufficient response to plasma therapies. Eight patients (28.5%) were only treated with Soliris, while five (17.8%) only received plasma-based therapies.

Also, 21 patients (75%) required kidney replacement therapy during the acute stage of the disease.

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Researchers call for more studies focusing on adolescence-onset patients

Overall, remission of the disease’s effects on blood parameters was achieved by 25 patients (89.3%), whereas remission from its effects on the kidneys was attained by 17 patients (60.7%). However, only 10 patients achieved complete disease remission, a significantly lower rate compared with infantile-onset patients (35.7% vs. 73.6%).

Genetic analysis was conducted for all patients, and in 11 (39.3%) a genetic variant associated with aHUS was detected.

After a mean follow-up of about five years, almost half (48.1%) of the patients with adolescence-onset aHUS had an estimated glomerular filtration rate, a measure of kidney function, within the normal range. This proportion was significantly lower compared with infantile-onset patients (82.6%).

Adolescence-onset aHUS is a rare disease but tends to cause more permanent [kidney] dysfunction than infantile-onset aHUS. … These results may modify the management approaches in these patients.

Moreover, adolescence-onset patients had significantly higher rates of end-stage kidney disease than did those with infantile-onset disease (14.8% vs. 2.2%). At the last visit, three patients were on chronic dialysis, and one had received a kidney transplant.

“Adolescence-onset aHUS is a rare disease but tends to cause more permanent [kidney] dysfunction than infantile-onset aHUS,” the researchers wrote, adding that “these results may modify the management approaches in these patients.”

The team also called for more research into aHUS beginning in adolescence, noting that they found no studies in the literature specifically focused on these preteen and teenaged patients.

“Further studies focusing on this age group will provide more insight regarding the age-specific clinical and genetic features as well as therapeutic strategies,” the researchers concluded.