Rare type of kidney damage seen in woman with CAD
Cold agglutinins may have been responsible for kidney damage, researchers say
A woman with cold agglutinin disease (CAD) developed a rare type of kidney damage caused by the accumulation of faulty antibodies inside small blood vessels, a case study shows.
This accumulation is also known as intracapillary deposits of monoclonal immunoglobulin M (IgM) antibodies.
“To the best of our knowledge, this is the first case report of intracapillary [monoclonal] IgM deposits occurring in association with cold agglutinin disease,” researchers wrote, adding it’s possible that cold agglutinins, the self-reactive antibodies that drive CAD, may have been responsible for that type of kidney damage as well.
The woman’s condition partially improved after chemotherapy, so identifying this type of kidney damage in CAD patients and starting treatment as early as possible may improve outcomes, researchers noted.
The case report, “Intracapillary Monoclonal IgM Deposition Concomitant With Cold Agglutinin Disease,” was published in Kidney Medicine.
CAD occurs when cold agglutinins bind to red blood cells at cold temperatures
CAD occurs when cold agglutinins, which are most commonly of the IgM type, bind to red blood cells at cold temperatures, causing them to clump and to be marked for destruction, or hemolysis.
Symptoms of CAD include anemia, fatigue, and numbness or discoloration of the extremities in response to cold temperatures. Anemia refers to low levels of red blood cells or of the hemoglobin protein inside these cells that transports oxygen.
The two main types of CAD are primary CAD, which occurs without a known cause, and secondary CAD, which develops as a result of other diseases, such as blood cancers or infections.
Antibodies, including cold agglutinins, are produced by immune B-cells and classified as monoclonal when produced by a single B-cell — typically the case of CAD-associated blood cancers — and polyclonal when they are generated by multiple, different B-cells.
A group of kidney diseases called monoclonal gammopathy of renal significance (MGRS) is caused by an overgrowth of a single B-cell. Kidney damage associated with the accumulation of monoclonal IgM antibodies inside kidney’s blood vessels is a rare manifestation of MGRS.
Now, a team at the Mayo Clinic in Rochester, Minnesota, described what may be the first reported case of this type of kidney damage in a CAD patient.
The woman, who was in her 60s, was referred to a kidney specialist because her kidney function was getting worse.
Three years before, she had been diagnosed with a marginal zone lymphoma, a slow-growing blood cancer that begins in B-cells. She was also diagnosed with CAD based on a positive direct Coombs test, which looks for antibodies and other immune proteins bound to red blood cells.
Woman previously treated with rituximab
The woman had been treated with rituximab, a medication that depletes B-cells, and her symptoms eased. The last rituximab dose had been given about 1.5 years before her kidney specialist appointment. At that visit, the woman reported mild fatigue and “frequent episodes of her extremities turning bluish when exposed to cold,” the researchers wrote.
Lab work showed hematuria (blood in her urine) and proteinuria (protein in her urine), which are signs of kidney damage. The woman still tested positive in the direct Coombs test and showed excessive amounts of abnormal, monoclonal IgM antibodies.
A kidney biopsy, where a small piece of kidney tissue is examined under a microscope, showed kidney damage was caused by IgM antibodies, which had built up inside the small blood vessels of her kidneys. These findings indicated MGRS with an intracapillary monoclonal IgM deposition pattern.
The woman received rituximab plus bendamustine, a chemotherapy. After one year of treatment, her IgM levels normalized, kidney function improved, hematuria resolved, and proteinuria lessened.
Before seeing a kidney specialist, the woman “had persistent positive direct [Coombs] tests and intermittent drops in her hemoglobin followed by fast recovery, likely due to flares of … hemolysis,” the researchers wrote.
As such, while CAD and intracapillary deposits of monoclonal IgM in this case “may be purely coincidental,” it’s possible that binding of cold agglutinins to red blood cells and subsequent reactions may have mediated “the co-occurrence of these 2 processes,” the researchers added.
This case highlights the importance of recognizing MGRS in patients with blood diseases, as it can lead to kidney damage. Early detection and treatment can help prevent worsening kidney function and improve outcomes.
While “clinical manifestations [of MGRS] are variable,” the researchers wrote, “prompt recognition of these manifestations is fundamental for early diagnosis of kidney involvement …, which has implications in management and clinical outcome.”
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