Pulmonary function tests and diffusing capacity for carbon monoxide in patients with psoriasis and their association with severety of disease

Objective: In this study, we aimed to assess pulmonary function tests(PFT) including diffusing capacity for carbon monoxide in the non-smokers patients with psoriasis with no lung disease and symptoms. Furthermore, to investigate the influence of psoriasis severity, PASI score, duration of psoriasis, MTX therapy, age at disease onset, PsA and DM on PFT parameters. Materials and Methods: In our study, 91 patients with psoriasis who were treated and followed up Bezmialem Vakıf University Faculty of Medicine, Department of Dermatology between 2015 and 2016 years and who were never-smokers and had no pulmonary disease and symptoms were recruited. These patients were further classified into mild psoriasis(mPsO) for those who had only received topical medication and moderate to severe psoriasis(sPsO) for those who had received phototherapy and/or systemic therapy. Additionally moderate to severe psoriatic patients were divided into two groups based on methotreaxate(mtx) treatment. MTX(+) sPsO for those who had received mtx therapy at least 3 months and MTX(-) sPsO for those who had no mtx therapy. Demographic, clinical features and spirometry, DLCO results of all patients following; age, sex, body mass index(BMI), ages at disease onset, early or late onset of the disease(type 1 or 2 psorisis), PASI score, severity or duration of psoriasis and comorbidities such as PsA, DM and FVC, FEV1, FEV1/FVC, FEF25-75, DLCO, DLCO/VA values were recorded. Results: 91 patients with psoriasis, 22(24,2%) of patients were male and 69(75,8%) of them were female, with a mean age of 41,2±14 years, with a mean age at disease onset of 28±14,2 years, mean BMI of 30±6,3kg/m2 and with a median disease duration of 10(1-38) years, a PASI score of 2,2(0-12,5). 69(75,8%) of whom were type 1 psoriasis. Of the 91 patients with psoriasis, 21(23,1%) had PsA, 10(11%) had DM and 34 were mPsO and 57 were sPsO(30 MTX(+), 27 MTX(-)). There was no significant difference age, sex, BMI, ages at disease onset, psoriasis in patients with early onset between the groups. A statistically significant difference was found between the groups regarding PASI score, duration of psoriasis, PsA and DM (p<0,001, p=0,014, p<0,001, p=0,002; respectively). Simple spirometry and/or DLCO disturbances were detected in 53(58,2%) of the patients. Spirometry results of 5 psoriatic patients were excluded due to failing orientation. Of the remaining 86 patients, 21(24,4%) had small airway obstruction (SAO), 1(%1,2) had restrictive dysfunction. None of them had large airway obstruction. In terms of SAO, of the 21 patients with psoriasis, 10(35,7%), 9(36%) and 2 (6,1%) respectively were in the MTX(+)sPsO, MTX(-)sPsO and mPsO group. There was significant difference in the patients with SAD between the groups (p=0,006). According to DLCO findings, of the 91 patients, 35 (38,5%) DLCO and 12 (13,2%) DLCO/VA impairment(<80% of predicted value) were found. There was no significant difference in the DLCO and DLCO/VA impairment between the groups(p > 0.05). When the PFT values (FVC, FEV1, FEV1/FVC, FEF25-75, DLCO, DLCO/VA) of the groups were compared, sPsO psoriatic patients showed a statistically significant reduction in the FEV1, FVC, FEV1/FVC, FEF25-75 values (p<0,001, p=0,033, p=0,041, p=0,012; respectively). Also we found significantly negative correlations between the PASI score and FEV1, FEV1/FVC, FEF25-75 values (r=-0,234, p=0,030; r= -0,225 p=0,037; r=-0,215,p=0,047; respectively) but no significant correlation between the disease duration and PFT values. There was no significant effect of mtx therapy, age at disease onset, PsA and DM on PFTs Conclusion: PFT values of psoriasis patients may deteriorate despite the absence of any respiratory disease, symptoms and smoking status. While spirometric abnormalities increase with severity of psoriasis, DLCO abnormalities can be seen in both mild and moderate-severe psoriasis. Therefore, we suggest that PFTs may be useful in early diagnosis of latent respiratory system diseases in psoriasis patients.