Dear Editor, Severe acute respiratory syndrome coronavirus 2 has spread across the globe, causing respiratory manifestations of coronavirus disease (COVID)‐19 and satisfying the epidemiological criteria for a pandemic. 1 As of 1 April 2020, more than one million cases testing positive for COVID‐19 have been identified and more than 54 000 deaths have occurred worldwide (https://systems.jhu.edu). In Italy, 110 574 positive cases, 49 285 hospitalized patients and 13 155 deaths from a population of 60 359 546 inhabitants were reported. 2 The highest number of deaths occurred in the northern Italian regions, i.e. Lombardy, Emilia‐Romagna, Veneto and Piedmont. 3

Intermittent circadian fasting, namely Ramadan, is a common worldwide practice. Such fasting has a positive impact on psoriasis, but no data exist on its role in psoriatic arthritis (PsA)—a disease that is clearly linked to body mass index. We enrolled 37 patients (23 females and 14 males) with a mean age 43.32 ± 7.81 and they fasted for 17 h for one month in 2016. The baseline PsA characteristics were collected and 12 (32.4%) patients had peripheral arthritis, 13 (35.1%) had axial involvement, 24 (64.9%) had enthesitis, and 13 (35.1%) had dactylitis. Three patients (8.1%) were treated with methotrexate, 28 (75.7%) with TNF-α blockers, and 6 (16.2%) with IL-17 blockers. After a month of intermittent fasting, C-reactive protein (CRP) levels decreased from 14.08 ± 4.65 to 12.16 ± 4.46 (p < 0.0001), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) decreased from 2.83 ± 1.03 to 2.08 ± 0.67 (p = 0.0078), Psoriasis Area Severity Index (PASI) decreased from 7.46 ± 2.43 to 5.86 ± 2.37 (p < 0.0001), and Disease Activity index for PSoriatic Arthritis (DAPSA) decreased from 28.11 ± 4.51 to 25.76 ± 4.48 (p < 0.0001). Similarly, enthesitis improved after fasting, with Leeds Enthesitis Index (LEI) decreasing from 2.25 ± 1.11 to 1.71 ± 0.86 (p < 0.0001) and dactylitis severity score (DSS) decreasing from 9.92 ± 2.93 to 8.54 ± 2.79 (p = 0.0001). Fasting was found to be a predictor of a decrease in PsA disease activity scores (DAPSA, BASDAI, LEI, DSS) even after adjustment for weight loss. IL-17 therapy was found to be an independent predictor of decreases in LEI after fasting. These preliminary data may support the use of chronomedicine in the context of rheumatic diseases, namely PsA. Further studies are needed to support our findings.

Fasting during the month of Ramadan consists of alternate abstinence and re-feeding periods (circadian or intermittent fasting). Nothing is currently known on the impact of this kind of fasting on psoriasis. A sample of 108 moderate-to-severe plaque psoriasis patients (aged 42.84 ± 13.61 years, 62 males, 46 females) volunteered to take part in the study. A significant decrease in the “Psoriasis Area and Severity Index” (PASI) score after the Ramadan fasting (mean difference = −0.89 ± 1.21, p < 0.0001) was found. At the multivariate regression, the use of cyclosporine (p = 0.0003), interleukin-17 or IL-17 blockers (p < 0.0001), and tumor necrosis factor or TNF blockers (p = 0.0107) was independently associated with a low PASI score, while the use of apremilast (p = 0.0009), and phototherapy (p = 0.0015) was associated with a high PASI score before the Ramadan fasting. Similarly, the consumption of cyclosporine (p < 0.0001), IL-17 blockers (p < 0.0001), mammalian target of rapamycin or mTOR inhibitors (p = 0.0081), and TNF blockers (p = 0.0017) predicted a low PASI score after the Ramadan fasting. By contrast, narrow band ultraviolet light B or NB-UVB (p = 0.0015) was associated with a high PASI score after Ramadan fasting. Disease duration (p = 0.0078), use of apremilast (p = 0.0005), and of mTOR inhibitors (p = 0.0034) were independent predictors of the reduction in the PASI score after the Ramadan fasting. These findings reflect the influence of dieting strategy, the biological clock, and circadian rhythm on the treatment of plaque psoriasis.

Hidradenitis suppurativa (HS) is a chronic-relapsing and debilitating disease, which affects the components of the folliculopilosebaceous unit and severely impacts on the perceived health-related quality of life. Among the possible treatments, dietary interventions, such as fasting, have been described to positively impact on HS. However, nothing is known about the effects of circadian, intermittent fasting, such as the Ramadan fasting. A sample of 55 HS patients (24 males (43.6%) and 31 females (56.4%), mean age 39.65 ± 8.39 years, average disease duration 14.31 ± 7.03 years) was recruited in the present study. The “Severity of International Hidradenitis Suppurativa Severity Score System” (IHS4) decreased significantly from 11.00 ± 5.88 (before Ramadan) to 10.15 ± 6.45 (after Ramadan), with a mean difference of −0.85 ± 0.83 (p < 0.0001). At the univariate analyses, the improvement was associated with HS phenotype (with a prominent improvement among those with ectopic type), treatment (with the improvement being higher in patients receiving topical and systemic antibiotics compared to those treated with biologics), the “Autoinflammatory Disease Damage Index” (ADDI), and Hurley scores. At the multivariate regression analysis, only the Hurley score (regression coefficient = 0.70, p = 0.0003) was found to be an independent predictor of change in the IHS4 score after fasting. The improvement in the IHS4 score was not, however, associated with weight loss. In conclusion, the Ramadan fasting proved to be safe and effective in HS patients. Considering the small sample size and the exploratory nature of the present investigation, further studies in the field are warranted, especially longitudinal, prospective and randomized ones.