en Infectious Diseases Infectious Diseases Original Article Original Article <span style="font-size:14px;"><span style="font-family:Times New Roman;"><span style="color:#0000ff;"><em><strong>Background: </strong></em></span>The northern coastal regions of Iran are endemic for leptospirosis which may range from a subclinical illness to a progressively fatal disease. There has been growing evidence that inflammatory markers play a significant role in the severity and prognosis of leptospirosis. This study aimed to investigate inflammatory cytokines in patients with leptospirosis.<br> <em><span style="color:#0000ff;"><strong>Methods: </strong></span></em>This descriptive-analytical prospective study was performed in 75 patients over 18 years old who had a positive microscopic agglutination test (MAT) titer from January to June 2019. SPSS software Version 20 was used for statistical analysis and the significance level was considered as p<0.05<span dir="RTL">.</span><br> <strong><em><span style="color:#0000ff;">Results:</span></em> </strong>The patients&rsquo; age enrolled in this study are from 21 to 75 years with a mean and standard deviation of 48.6 &plusmn; 14.0. The male to female ratio in our participants was 54/21. Fever was the most common symptoms in 66 (88.0%) patients, followed by myalgia in 62 (82.7%) cases. The level of interleukin 10 was significantly higher in severe illness (P=0.003) and fatal cases (p<0.028) compared with recovered patients. The level of TNF-&alpha; level was also higher in the severe illness and Weil&#39;s syndrome compared with the mild kind (P=0.022).<br> <span style="color:#0000ff;"><em><strong>Conclusion: </strong></em></span>Our results showed that the levels of TNF-&alpha; and IL-10 significantly increased in severe leptospirosis. Also, IL-10 was significantly higher in fatal cases. The inhibition of IL-10 production might play an important role in decreasing the risk of fatal outcomes in leptospirosis.</span></span> Leptospirosis, Inflammatory cytokine, treatment, outcome, IL10 343 348 http://caspjim.com/browse.php?a_code=A-10-2136-2&slc_lang=en&sid=1 Ahmad Alikhani ahalikhani@yahoo.com 100319475328460036499 100319475328460036499 No Department of Infectious Diseases, Antimicrobial resistance research center and communicable disease institute, Mazandaran University of Medical Sciences, Sari, Iran Kimia Mahmoodi edu.kimiamahmoodi93@yahoo.com 100319475328460036500 100319475328460036500 No Leila Delavaryan Leiladelavaryan@yahoo.com 100319475328460036501 100319475328460036501 No Ebrahim Salehifar esalehifar52@gmail.com 100319475328460036502 100319475328460036502 No Department of clinical Pharmacy, School of Pharmacy, Mazandaran University of Medical Sciences, Sari, Iran. Ali Reza Rafiei rafiei1710@gmail.com 100319475328460036503 100319475328460036503 No Department of Immunology, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran. Mahmoud Sadeghi Zavare drm_sadeghihz@yahoo.com 100319475328460036504 100319475328460036504 Yes Infectious Diseases and Tropical Medicine Research Center, Babol University of Medical Sciences, Babol