Autosomal-recessive deficiency of lymphocyte-specific protein tyrosine kinase (LCK) has been reported in a girl with early-onset recurrent respiratory tract infections, including pneumonia complicated by pneumatocele.123 This patient additionally displayed neutrophilic panniculitis, polyserositis, and recession after the introduction of a TNF inhibitor and ITP, suggesting immune dysregulation. Here, LCK is linked to pneumonia.