When we compared disease onset in anti-MDA5 positive patients with RP-ILD and patients without, it was found that while both groups had a dip in summer season from July to September (with RP-ILD: observed number 5, expected number 11.5, p = 0.032; without RP-ILD: observed number 10, excepted number 16, p = 0.028), a peak was noted from October to December only in the RP-ILD group (observed number 19). This evidence concerns the gene IFIH1 and retinitis pigmentosa 1.