Evaluation of Circulating Neutrophils in Antisynthetase Syndrome

Antisynthetase syndrome (ASyS) is a rare and heteregeneous overlapping connective tissue disease, characterized by myositis, interstitial lung disease (ILD), joint involvement, Raynaud's phenomenon and cutaneous manifestations ("mechanic's hands"). Over 50% of patients develop ILD, which is the leading cause of death.

The role of neutrophils - innate immune cells involved in inflammatory processes and induced in particular by cytokines of the Th17 pathway - during AS is unknown. Direct pathogenic role of neutrophils has been described during idiopathic inflammatory myopathies, with an increase of netosis correlated with disease activity and muscle damage. During ASyS, a higher number of alveolar neutrophils has been observed in patients with rapidly progressive ILD.

There are few data on the specific evaluation of circulating neutrophils in ASyS. Investigators suppose that circulating neutrophils level could represent a simple and accessible severity biomarker in patients with ASyS.

The main objective is to evaluate the diagnostic performance of the circulating neutrophils level (> 7000/mm3) at diagnosis on ASyS severity.

The secondary objectives are:

• to define a threshold for circulating neutrophils levels at diagnosis allowing to predict ASyS severity and to assess the diagnostic performance of this threshold.

• to study the correlation between the level of circulating neutrophils and ASyS severity at diagnosis of the disease.

• to compare the circulating neutrophils level at ASyS diagnosis and after 1 year of treatment.

• to compare patients characteristics according to ASyS severity at diagnosis.

• to compare BAL fluid neutrophils level according to ILD severity at ASyS diagnosis in patients with ILD.