Similarities and differences in autoinflammatory diseases with urticarial rash, cryopyrin-associated periodic syndrome and Schnitzler syndrome

Neutrophilic Urticarial Dermatosis: A Window into Systemic Inflammation and Autoimmune Disorders

Neutrophilic urticarial dermatosis (NUD) is a distinctive dermatological manifestation that is commonly associated with systemic autoinflammatory and autoimmune diseases. This review comprehensively explores NUD in the context of five major conditions: Schnitzler syndrome, Still's disease, cryopyrin-associated periodic syndrome, systemic lupus erythematosus, and VEXAS syndrome. For each condition, a detailed discussion of the underlying mechanisms, clinical presentations, diagnostic criteria, and treatment strategies is provided. In addition, cases exhibiting features similar to NUD are emphasized, with a comprehensive examination of the pathological characteristics, particularly focusing on neutrophilic epitheliotropism. This review underscores the significance of identifying NUD as a potential indicator of systemic autoimmune disorders and discusses the role of skin biopsy and laboratory tests in diagnosing the underlying etiology. Finally, a diagnostic framework for NUD is proposed, highlighting the importance of a multidisciplinary assessment to ascertain the underlying systemic condition responsible for the dermatological manifestations. The objective of this review is to enhance the comprehension of NUD, thereby facilitating early diagnosis and the implementation of targeted strategies for affected patients.

Investigator-initiated, multi-center, single-arm, open-label study of the effectiveness of canakinumab in Japanese patients with Schnitzler syndrome

BACKGROUND

Schnitzler syndrome is an adult-onset autoinflammatory disease characterized by an urticaria-like rash and monoclonal gammopathy with fever and fatigue. Although some treatments have shown efficacy in clinical trials, no approved treatment exists. We aimed to assess canakinumab, an anti-IL-1β monoclonal antibody, in Japanese patients.

METHODS

This phase II, multicenter, single-arm, open-label study enrolled five patients with active disease from four hospitals. Patients received a single subcutaneous dose of canakinumab 150 mg. The primary endpoint was the proportion of patients achieving a complete clinical response (CR), based on physician global assessment on Day 7. If a CR was not achieved on Day 7 or by 8 weeks post-treatment, the dose was increased to 300 mg. Dosing continued every 8 weeks until 24 weeks. The study also evaluated patient-reported disease activity and changes in acute inflammatory markers, including white blood cell count, neutrophil count, C-reactive protein concentration, and serum amyloid A level. Quality of life was assessed using the Dermatology Life Quality Index and the 36-item Short Form health survey. Safety was also evaluated.

RESULTS

Sixty percent (3/5) of patients had a CR on Day 7. One of the remaining two patients had a CR 7 days after the dose was increased to 300 mg. All five patients, including those who did not achieve a CR, showed improvement in inflammatory markers and quality of life scores, and no new adverse events were detected.

CONCLUSIONS

In this trial, canakinumab showed a potential for usefulness in Japanese patients with Schnitzler syndrome.

A 58-Year-Old Woman With Urticaria, Fever, and Joint Pain

A 58-year-old woman with no allergies or rheumatic disease had a 2-year history of spontaneous wheals that occurred daily, accompanied by pruritus, arthralgia, and intermittent fevers; the wheals resolved after several hours without residual hyperpigmentation or bruising. C-reactive protein level was elevated, and skin biopsy showed dermal neutrophilic infiltration. What is the diagnosis and what would you do next?

Background and Clinical Features of a Unique and Mysterious Autoinflammatory Disease, Schnitzler Syndrome

Schnitzler syndrome is a unique autoinflammatory disease, of which 747 cases have been described worldwide to date. The main features of the syndrome are a triad of recurrent urticaria, monoclonal IgM gammopathy, systemic inflammation associated with recurrent fever, joint and bone pain, and atypical bone remodeling (osteosclerosis). The abnormal activation of the NLRP3 inflammasome produces IL-1, which drives the disease pathology, but it also involves IL-6 and IL-18. Unlike other autoinflammatory diseases, Schnitzler syndrome lacks evidence of the gene divergence causing the abnormal activation of NLRP3. However, mutations in the MEFV and MYD88 genes can be associated with the development of the disease. Due to its rarity, diagnosing the disease can be a challenging task. IL-1 inhibitors (i.e., anakinra, canakinumab, and rilonacept) are prominent in the treatment of the disease, but the IL-6 receptor inhibitor tocilizumab and the Bruton's tyrosine kinase inhibitor ibrutinib are also promising alternatives. In this summary article, we aim to provide a comprehensive overview of the clinical and molecular background of the disease and potential therapeutic targets, based on the cases reported so far. We diagnosed a patient who, to the best of our knowledge, represents the 748th documented case of this specific pathology. In the context of this patient, we would also like to draw attention to the potential pathogenic role of two novel gene mutations (variants of the MEFV gene "c.2084A>G" and the F2 gene "3'UTR c.*97G>A").

Neutrophilic epitheliotropism, proposed as an auto-inflammatory condition of neutrophilic urticarial dermatosis including Schnitzler syndrome, is also observed in Japanese cases

Schnitzler syndrome (SchS) is a rare autoinflammatory disease characterized by bone pain, recurrent fever, leukocytosis, and elevated C-reactive protein, along with an urticaria-like rash and monoclonal immunoglobulin (Ig)M or IgG gammopathy. Notably, the condition is distinguished by a relatively persistent recurrent urticarial-like rash. Histopathological features observed in the skin comprise diffuse neutrophil infiltration into the dermis, absence of dermal edema, and vascular wall degeneration, all of which classify SchS as a neutrophilic urticarial dermatosis (NUD). Accumulated histological data from skin biopsies of patients with NUD have revealed a sensitive histopathological marker for NUD, acknowledged as neutrophilic epitheliotropism, which has been proposed as reflecting an autoinflammatory condition. In this report, we present three SchS patients: two men (ages 55 and 68) and a woman (age 75), all displaying neutrophilic epitheliotropism in their skin biopsy specimens. Additionally, a review of eight previously reported SchS cases in Japan identified neutrophilic epithliotropism in five cases. These findings suggest that the inclination of neutrophils toward the epithelial tissue could aid in confirming diagnoses of NUD in most cases that need to be differentiated from conventional urticaria. Consequently, we emphasize that acknowledging neutrophilic epithelial predilection as a hallmark of NUD is critical for expediting early diagnosis and appropriate treatment for SchS.