P133 Anti-synthetase syndrome: an experience from a tertiary referral center
Authors: Khatri Prabin , Durga J N , Yadavalli R , Dhuria Shahzeene , Negalur Natasha , Shivam Kumar , Gupta Rajiva 
Published: April 2024

Abstract

Background/Aims
Anti-synthetase syndrome (ASS) is a subset of Idiopathic inflammatory myositis (IIMs). It is a syndromic diagnosis classified by Connors et al. and Solomon et al. criteria. Raynaud’s phenomenon (RP), fever, arthritis, mechanics hands, ILD and myositis constitute this syndrome along with the classical Anti-aminoacyl tRNA synthetase antibodies (ARS). About 25% of IIMs patients are classified as ASS. This study was planned to evaluate the prevalence of ASS; their phenotype, antibody subtypes, treatment responsiveness and outcomes.

Methods
All consecutive ASS patients were enrolled in the study fulfilling Connors et al. criteria during January, 2016 to August2023. Their demographic details, clinical features, laboratory and imaging features, treatment were analyzed. ARS were considered positive on a Line Immunoassay with cutoff &gt;6U/ML using BlueDriverQuantrix-ANA25 Screen IgG kit (includes Jo1, Pl-7, Pl-12) from D-tek, Belgium including three ASS antibodies (Jo-1, PL-12, PL-7). Anti EJ, OJ antibodies were not present in the kit. Descriptive analysis were used to describe disease characteristics.

Results
Among 139 total IIM patients, 21(15%) patients were diagnosed with ASS. All patients fulfilled Connors et al. criteria while 66.6% patients fulfilled stricter criteria by Solomon et al. Mean(±SD) age group was 43(±16.4) years. 71.4% were Females. Anti Jo-1 was the predominant antibody seen in 66.6% while Anti PL-12 and Anti Pl-7 antibodies were present in 19% and 14.3% respectively. 66.6% had ANA positivity and MAA antibodies were seen in 52.3%. Rash was seen in 61.9%, mechanics hands in 38%, RP in 52.3% fever in 38% ,arthritis in 57%, myositis 62% and ILD in 80.9%. NSIP (66.6%) was the predominant type, followed by OP (9.5%) and UIP (4.7%). Median (IQR) CPK level was 736 (210-4556)U/L. Anti Jo-1 patients had higher prevalence of mechanics hands and rash whereas ILD was observed in all cases of Anti PL-7 and Anti PL-12 antibodies. Malignancy was seen in two patients (Malignant fibrous histiocytoma, Metastatic Pancreatic carcinoma). Mean (SD) MMT8 score was 62.8(±22.2) at presentation . Treatment is with steroids in all cases followed by maintenance with azathioprine in 57.1%, Methotrexate in 14.2%. Rituximab was used in 14.2%, cyclophosphamide in 9.5% and mycophenolate mofetil in 23.8%. Mortality was seen in one patient with respiratory failure. Lung involvement was severe in patients with both MSA and MAA positivity. 62% patients were in remission.

Conclusion
ILD and Arthritis were the main presenting complaints in our cohort. Myositis is relatively less prevalent in ASS. NSIP was the predominant ILD subtype. Non Jo-1 group had high MAA positivity. Jo-1 was associated with mechanic’s hands and rash. Malignancy was less prevalent in ASS. All patients with PL-7 and PL-12 antibodies had lung involvement. Biologics were required in few refractory cases.

Disclosure
P. Khatri: None. J.R. Yadavalli: None. S. Dhuria: None. N. Negalur: None. K. Shivam: None. R. Gupta: None.