Pregnancy ID’d as trigger event for aHUS in woman, 25: Case study

Symptoms of kidney damage resolved after Soliris, plasma exchange

Patricia Inácio, PhD avatar

by Patricia Inácio, PhD |

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A pregnant woman cradles her belly with one hand while holding a teddy bear in the other.

Pregnancy was identified as the trigger event for atypical hemolytic uremic syndrome (aHUS) that resulted in kidney damage for a genetically predisposed woman in her mid-20s, a U.S. case study reported.

The patient had a clinical history of poorly managed high blood pressure and often failed to comply with treatment, according to the study’s author.

Nonetheless, clinicians were able to resolve her symptoms with Soliris (eculizumab), an approved aHUS medicine, and plasma exchange therapy.

“This case shows the potential of severe [kidney] manifestation of aHUS, and the need for a kidney biopsy in cases of severe uncontrolled hypertension presenting with kidney injury. If evidence of aHUS is found, prompt treatment with plasma exchange and [Soliris] should be initiated,” the physician wrote.

The woman’s case was detailed in a report, “Atypical Hemolytic Uremic Syndrome in a Pregnant Patient with a Thrombomodulin Gene Variant Treated with Plasma Exchange and Eculizumab,” published in the American Journal of Case Reports.

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For woman genetically predisposed to aHUS, pregnancy serves as trigger event

aHUS belongs to a larger group of disorders called thrombotic microangiopathies, or TMAs. These disorders are characterized by the formation of tiny blood clots in small blood vessels that block blood flow to important organs, especially the kidneys. Typically, patients also show signs of red blood cell destruction and have low platelet counts.

In most cases, aHUS is associated with mutations in the genes that regulate the complement cascade, resulting in its abnormal activation. The complement system is a set of more than 30 proteins that is part of the body’s immune defenses.

However, while genetic mutations can predispose individuals to develop aHUS, in almost all cases an additional trigger event, such as an infection or pregnancy, is needed for the disease to develop.

Here, a physician at the Pikeville Medical Center, in Kentucky, described the case of a pregnant 25-year-old woman who developed aHUS. The patient had a clinical history of hypertension but despite being medicated, she did not closely follow her treatment regimen.

She was treated at the hospital for nausea, severe headaches, and vomiting. Her blood pressure was high, a sign of hypertension, and she showed signs of acute kidney injury.

In subsequent visits due to uncontrolled hypertension, her medications were switched. While kidney function remained stable, the amount of proteins in her urine was elevated, suggestive of kidney dysfunction.

After failing to attend follow-up visits for one year, the patient was treated again at the hospital for the same symptoms. She also was nine weeks pregnant.

Lab tests revealed she had anemia, or a low number of red blood cells, low platelet counts, and a low estimated glomerular filtration rate — a sign of poor kidney function.

She was admitted to the intensive care unit (ICU) and given several medications to control her blood pressure.

A peripheral blood smear showed the presence of red blood cell fragments, called schistocytes, which are characteristic of TMAs. A kidney biopsy confirmed the presence of tissue damage consistent with TMA.

She was treated for three days with fresh frozen plasma (FFP), used to replace the non-cellular portion of blood. FFP was given due to suspicion of a potential inherited form of thrombotic thrombocytopenic purpura, a type of TMA.

The patient was discharged again, with instructions to take several medications to control her blood pressure, but returned to the hospital at 20 weeks of pregnancy with similar symptoms.

Her blood pressure normalized following treatment, but physicians opted to induce labor to avoid further complications. She continued to be medicated for her blood pressure.

This case shows the potential of severe [kidney] manifestation of aHUS, and the need for a kidney biopsy in cases of severe uncontrolled hypertension presenting with kidney injury.

On the day of admission, she received two FFP units and other two units the second day. However, she started experiencing shortness of breath, chest pain, and increased oxygen requirements due to transfusion-associated circulatory colapse (TACO) — a life-threatening complication that can occur during or after a blood transfusion due to excessive fluid buildup in the body.

She was transferred to the ICU due to her worsening respiratory condition and was ultimately intubated for respiratory distress. TACO was resolved with the initiation of hemodialysis — a treatment that filters waste from the blood when the kidneys can no longer perform their normal function adequately — and after switching to plasma exchanges.

In suspicion of a complement-mediated TMA, doctors ordered a genetic test that confirmed the patient carried a mutation in the THBD gene, which is found in a small proportion of aHUS cases.

At discharge, she was started on Soliris. In an outpatient follow-up visit, after four doses of Soliris, her hemoglobin and platelets levels were stable, indicative of a treatment response. Hemoglobin is the oxygen-carrying protein in red blood cells.

Overall, this case highlights the need to “screen for TMA in patients who present with severe uncontrolled hypertension, [acute kidney injury], and other features of TMA,” the author wrote.

“Prompt treatment with plasma exchange and terminal complement factor inhibitor is necessary to prevent progression of kidney disease,” the author wrote.