PIK3C2A and interstitial lung disease: Similarly, no significant differences in the serological biomarkers analyzed were found between ILD patients reporting or not reporting post-COVID-19 fatigue, except for differences in CPK levels (p = 0.015, Table 3) and lymphocyte count: CPK levels (mean difference: 69.7, 95%CI 12.7 to 126.7, p = 0.015) and lymphocyte count (mean difference: 0.4, 95%CI 0.1 to 0.7, p = 0.037) were significantly higher in ILD patients with post-COVID-19 fatigue than in those without post-COVID-19 fatigue (Table 3).