The clinical characteristics most strongly associated with the development of IP were boys, age >5 years, wheezing history, hydrothorax free, lymphocyte counts (>3.0 × 109/L), CD19+ (>0.9 × 109/L), CD3+ (>2.5 × 109/L), CD4+ (>1.5 × 109/L), CD8+ (>0.9 × 109/L), IL-6 (<30 pg/ml), IL-10 (<6 pg/ml), and IFN-γ (<15 pg/ml) compared with children with PC. Here, CD19 is linked to pachyonychia congenita.