December 2021

There are some arguments on whether neutrophilic urticaria (NU) is distinct from chronic spontaneous urticaria (CSU), although with no consensus. This study aimed to compare clinical, biological, and histological characteristics and therapeutic responses between NU and CSU.

This was an observational, retrospective study that included adults with chronic urticarial rash who had undergone a skin biopsy. One dermatologist and one cytopathologist blindly and independently reviewed the biopsies [cytology counting technique for a precise proportion of neutrophilic/eosinophilic polynuclear cells (PNN/PNEo)]. NU was defined by an inflammatory dermal infiltrate composed of at least 60% PNN, without leukocytoclasia/vasculitis.

Forty-four patients were included, and their biopsies were classified into two groups: NU (n=28) and CSU (n=16). From the bibliography, there are no characteristics related to PNN at histology, but an increase in erythrocyte sedimentation rate in the NU group (p=0.03). Colchicine also showed to be more effective in cases of significant neutrophilic infiltrate: 42.85% effectiveness in NU group versus 6.25% in CSU group.

Two other findings were a statistically associated relation with neutrophilic venulitis (p=0.04) (corresponding to an intraparietal aggregation of PNN without vasculitis) and a basophilic interstitial flame figure corresponding to degranulation of the PNN cytoplasm and exclusively associated with NU (p=0.04).

A diagnostic score was established using strict quantitative histological criteria (intensity of neutrophilic infiltrate, the existence of neutrophilic venulitis, basophilic flame figures, and intense leukocytoclasia), which allows the classification of urticarial eruptions into NU or UCS.

This score will allow diagnosis and homogenization of NU patients (it correctly classified 40 of the 44 patients from the study).

In conclusion, NU is an independent entity as some histological images were significantly (neutrophilic venulitis) or exclusively (basophilic flame figure) associated with an intense neutrophilic infiltrate. A prospective study is needed to validate this new score.

Chronic spontaneous urticaria (CSU) is a common condition in adults and children, impacting the quality of life. Recent studies characterized chronic spontaneous urticaria as an autoantibody-driven condition, with mast cells and basophils being activated through two distinct pathways: type I autoimmune CSU, where IgE autoantibodies are cross-linked by self-antigens; and type IIb autoimmune CSU, where IgG and IgM autoantibodies are directed against IgE receptors on the surface of mast cells and basophils. Basophil testing is the most effective way to diagnose type IIb autoimmune CSU: a positive basophil test correlates to long disease duration, higher disease activity, poor response to antihistamines and omalizumab, and a better response to cyclosporine and fenebrutinib.

The objective of this study was to identify features of basophil test-positive patients.

This was a cross-sectional study that included 85 participants with CSU. They were tested for basophils with the basophil-activation test (BAT), the basophil histamine release assay (BHRA), and data were statistically analyzed.

Of all the participants, 44% tested positive with the BAST, and 28% tested positive with BHRA. These participants had higher activity and impact of disease, less disease control, and lower total serum IgE. In contrast, they had a higher rate of positive autologous serum skin test (ASST), angioedema, nocturnal symptoms, symptoms more than five days/week, and thyroid autoantibodies. The ASST was a good predictor of a positive basophil test when combined with angioedema, thyroid autoantibodies, and low IgE.

This study showed that a positive basophil test is related to known characteristics of type II autoimmune CSU, allowing a better approach to these patients’ condition management.