Lupus may alter iTTP symptoms, outcomes: Study

People with immune-mediated thrombotic thrombocytopenic purpura (iTTP) who also have systemic lupus erythematosus (SLE) — have different symptoms and longer periods without disease relapse than those who have iTTP alone, a study found.

Neurological symptoms were less common, but cardiac symptoms more common, in people who had both diseases.

“Our study highlights … that patients with SLE-iTTP have distinct clinical features and outcome,” the researchers wrote. “Further studies focused on well-characterised SLE-iTTP populations and interdisciplinary collaborations might help to better characterise and manage patients with this rare entity.”

The study, “Immune-mediated thrombotic thrombocytopenic purpura with systemic lupus erythematosus: clinical features and outcome,” was published in Lupus Science & Medicine.

iTTP, also known as acquired TTP, is a rare and serious blood disorder in which small blood clots form in blood vessels, leading to organ damage and low blood cell counts. It arises when the immune system mistakenly produces self-reactive antibodies that prevent the proper function of ADAMTS13, an enzyme that normally prevents blood clots from forming when they aren’t needed.

Investigating the link between iTTP and SLE

Certain other autoimmune diseases, including SLE — often called lupus — are considered risk factors for iTTP. In lupus, the immune system generates self-reactive antibodies that can target virtually any of the body’s tissues.

iTTP has been reported to occur in up to 4% of people with SLE, according to the study’s authors. But accurately diagnosing iTTP-SLE can be difficult, because doctors don’t have a clear picture of how the combined conditions look.

The researchers set out to better characterize iTTP-SLE. They analyzed clinical data from 1,409 people diagnosed with iTTP who were included in an observational study (NCT00426686) conducted in France.

At the time iTTP was diagnosed, 6% of the participants had a prior or concurrent SLE diagnosis, while 31% had tested positive for antinuclear antibodies (ANAs) — a type of SLE-associated antibody — but didn’t have clinical features of SLE. The remaining 63% did not show any biological or clinical signs of SLE.

The study’s main analysis focused on 67 people diagnosed with iTTP-SLE, 13 of whom were also diagnosed with another autoimmune disease. Also included were 67 iTTP patients without SLE or with idiopathic iTTP, of whom 24 tested positive for SLE-associated antibodies.

Significantly more people with idiopathic iTTP exhibited neurological involvement than those with iTTP-SLE (46% vs. 27%), while heart problems were significantly more common in iTTP-SLE (16% vs. 4%). The rate of kidney issues was comparable between the two groups.

Those with iTTP alone more commonly received plasma exchange therapy, which helps filter out disease driving antibodies from the blood (99% vs. 85%).

While the use of treatments such as corticosteroids, rituximab, and Cablivi (caplacizumab-yhdp) was similar between the groups, people with iTTP-SLE more often received other therapeutic agents, particularly nonsteroidal immunosuppressants.

Responses to treatment were similar overall, but disease flares occurred more often in people who only had iTTP than in those who also had SLE (48% vs. 22%).

Over a median follow-up of close to six years, the time spent without clinical or biological signs of a disease relapse, called relapse-free survival, was significantly shorter in people with idiopathic iTTP than in those with SLE-iTTP.

When considering relapse-free survival in terms of clinical features of a flare-up, the two groups didn’t differ. But when defining it based on a drop in ADAMTS13 activity in the blood, it was significantly shorter in people with idiopathic iTTP.

The researchers noted that the higher use of immunosuppressive therapies among those with SLE could have led to improved disease control, “underscoring the need for tailored management strategies in this population.”

No person with idiopathic iTTP developed SLE during follow-up, but of the 437 people who tested positive for ANAs out of the larger group of 1,409 people, 8% were later diagnosed with SLE and 7% developed another systemic autoimmune condition.

Given this relationship, “ANAs should be systematically assessed on iTTP diagnosis, and a specific follow-up should be offered to these patients to assess early features suggestive of SLE before overt complications,” the researchers wrote.