Undifferentiated autoinflammatory disease in adults: a prospective study in 61 patients.

Backgrounds: Undifferentiated or undefined systemic autoinflammatory disease (uSAID) encompasses a group of rare, heterogeneous diseases characterized by the features of well-defined systemic autoinflammatory diseases (SAIDs), but lacking diagnostic phenotypes or genetic confirmation. We aimed to describe the phenotypes, genotypes and treatment responses of Chinese adult patients with uSAID.

Methods: The final diagnosis of uSAID was reached in 61 patients, whose organ-specific inflammation was compared and three subgroups were identified based on phenotypic similarities to well-defined SAIDs. Phenotypes, genotypes and treatment responses were analyzed in these subgroups.

Results: Among the 61 uSAID patients, 17 had disease-onset during childhood, and 44 had adult-onset. Compared to those without pulmonary manifestations, patients with pulmonary involvement exhibited higher frequencies of myalgia, skin lesions, cardiac involvement, gastrointestinal involvement, urinary involvement, lymphadenopathy, headache, and intellectual impairments. Twenty-four patients exhibited monogenic SAID-like phenotypes, 12 had polygenic SAID-like phenotypes, and the remaining 25 were categorized as having atypical phenotypes. Among the 53 patients followed, 25% (13/53) improved spontaneously with complete or partial recovery independent of therapy. Patients with atypical phenotypes had the highest spontaneous remission rate (10/23, 43%).

Conclusion: This study is the first to describe the clinical and genetic features of a cohort of Chinese adult patients with uSAID. Patients with pulmonary manifestations may be more prone to developing complex phenotypes, while those with atypical phenotypes have a high rate of spontaneous remission, indicating a favorable prognosis.