AAE linked to SLE, lupus nephritis in woman, 22: Case report

Case was unique because lupus nephritis was only SLE symptom, C1-INH protein was normal

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by Andrea Lobo |

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A 22-year-old woman with systemic lupus erythematosus (SLE), the most common form of lupus, developed acquired angioedema (AAE), a recent case report notes.

“AAE may happen in adolescents and young adults. It could be an early manifestation of SLE,” the researchers wrote, adding that “practitioners must be aware of this uncommon disease linked with SLE in adolescents and young adults.”

The woman’s case was described in “Angioedema in the Absence of C1 Esterase Inhibitor Deficiency in a Young Patient With Anti-dsDNA Negative Lupus Nephritis,” which was published in Cureus.

Angioedema refers to the swelling of the skin or the mucosal lining of the respiratory and digestive tracts. AAE constitutes 6-10% of all angioedema cases and may or may not be associated with a deficiency in the levels or function of the C1-inhibitor (C1-INH) protein.

C1-INH blocks the activity of two proteins that promote the production of bradykinin, a signaling molecule that regulates blood pressure and inflammation by promoting blood vessel widening. When C1-INH levels are low, bradykinin levels get too high, letting fluid leak from the bloodstream into nearby tissues, causing swelling.

This type of angioedema may manifest with an underlying condition, such as an autoimmune disease like SLE.

Researchers described the unusual case of a 22-year-old woman with SLE who developed AAE. Swelling affected her upper airways and required her to be intubated.

The woman had a previous history of chronic hepatitis B infection and presented with lower extremity swelling, dark urine, and weight gain. She had no fever and her blood pressure, heart rate, and oxygen blood saturation levels were normal. A physical examination revealed pitting edema in the legs up to the knees.

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A unique case

Blood tests showed low hemoglobin levels, high C-reactive protein levels — indicative of inflammation — high creatinine levels, and low levels of albumin, suggesting kidney and/or liver damage. Hemoglobin is the protein in red blood cells responsible for oxygen transport. A kidney ultrasound showed signs of kidney damage.

Advanced laboratory tests revealed anti-nuclear antibodies (ANAs), which target molecules found in a cell’s nucleus, where its genetic information is contained. These antibodies are often found with SLE.

The woman tested negative for other antibodies commonly found with SLE, including anti-double-stranded DNA and anti-Smith antibodies. An analysis of the complement system, a part of the immune system, showed low levels of C3 and C4 complement proteins.

The woman had a kidney biopsy that found signs of kidney damage compatible with lupus nephritis, a common complication of lupus that’s marked by damage to the kidneys.

She was started on immunosuppressants (mycophenolate mofetil, tacrolimus), oral steroids, and diuretics. On the third day after being admitted, she said her throat was swelling, which a CT scan showed involved several structures, including the vocal cords. She was intubated to protect her airways.

The “early detection and treatment of such cases can lead to an outstanding prognosis by preventing airway compromise and anoxic brain injury [damage caused by the reduction of oxygen delivery to the brain],” the researchers said.

Further evaluation for angioedema revealed normal C1-INH levels and function, with low levels of another complement protein called C1q. She started on high-dose, into-the-vein steroids, while continuing immunosuppressants.

The woman was discharged and at follow-up said she had no more throat swelling. A repeat analysis three months after being discharged revealed normal C1q levels and stable kidney function.

The case was deemed unique because the woman’s only SLE symptom was lupus nephritis, she developed AAE at a relatively early age, and she had normal C1-INH levels with low C3.

“The level and function of C1-INH may be normal in SLE patients who develop [angioedema]. The potential mechanism behind this type of angioedema is a complex interplay of both bradykinin and mast cell pathways and is likely related to massive complement activation and a transient rise in bradykinin levels,” the researchers wrote.