Background
Systemic sclerosis is a rare connective tissue disorder, characterized by microvascular damage, dysregulation of innate and adaptive immunity, and multi-organ fibrosis. Despite the availability of different treatment modalities, systemic sclerosis has a greater mortality rate than other rheumatic diseases. Our study aimed to describe current treatment modalities, determination of the drug survival rates and evaluation of the discontinuation factors of the commonly used treatment modalities in Egyptian systemic sclerosis patients which highlights their practical effectiveness and safety.

Methods
This retrospective study included 63 systemic sclerosis patients. Demographic, clinical and therapeutic data, including the exact date of each drug’s initiation and discontinuation, as well as the reason for discontinuation were analyzed. Survival probabilities were estimated by the Kaplan-Meier method.

Results
Methotrexate was the most frequently administered immunosuppressant (87.3%) among the study patients, followed by azathioprine (50.7%). The estimated continuation probabilities of azathioprine, methotrexate, mycophenolate mofetil, and prednisolone differed significantly (p < 0.001). Azathioprine demonstrated the highest continuation rate among the studied immunosuppressive drugs, remaining at 96.6% at 12, 24, 36, and 48 months. In comparison, survival rates of methotrexate, mycophenolate mofetil and prednisolone were 80.3/68.8/59.3/56.5%, 61.1/30.6/ 30.6/- % and 40.1/-/-/-% at 12/ 24/ 36/ 48 months, respectively. The occurrence of adverse effects was the most frequent discontinuation cause (46.77%). Patients with shorter disease duration at the time of methotrexate initiation had a higher risk of discontinuing it (p = 0.012).

Conclusion
Azathioprine showed the highest survival rate among the studied immunosuppressive drugs, reflecting its safety and tolerability. The continuation rates of other immunosuppressive drugs are relatively low. Therapy should be tailored for each patient to improve the long-term management of systemic sclerosis patients.