Cholinergic urticaria in patients with systemic lupus erythematosus: Coincidence or immunological connection?

Abstract

BACKGROUND
Cholinergic urticaria (CU) is a disease that affects 1.5% of the population in Latin America. Patients with CU have been shown to have a fivefold increased risk of systemic lupus erythematosus (SLE).

CASE REPORT
A 22-year-old female patient with a history of cholinergic urticaria treated with immunotherapy without improvement and with partial improvement with antihistamines presented six months prior with headache, malaise, dry skin, persistent wheals, and arthralgia in the distal phalanges and knees. The following paraclinical tests were requested: Anti-CCP, anti-DNA, negative beta-2 glycoproteins, positive antinuclear antibodies (1:90, homogeneous nuclear pattern), anticardiolipin IgG (34), and low complement C3-C4. The patient was diagnosed with SLE as they met 16 points of the EULAR criteria. They are currently being treated with chloroquine and prednisone with improvement in symptoms. Figure 1

DISCUSSION
There are two theories that can explain the association between both diseases. The first is shared immunopathogenesis. It has been demonstrated that patients with cholinergic urticaria have elevated levels of anti-dsDNA and anti-C1q, both specific markers for SLE. Furthermore, the increase in IgG against the α subunit of IgE plays an important role in mast cell activation in cholinergic urticaria, thus triggering systemic autoimmunity and progressing to SLE later in life. There is a shared risk associated with HLA-DRB1*04 that is linked to both systemic lupus erythematosus (SLE) and cholinergic urticaria.

CONCLUSIONS: There is limited information regarding the association between these diseases, and no incidence rate has been established. However, it has been shown that patients with cholinergic urticaria have a significantly higher risk of developing SLE.