In LAD-I patients, the paucity of neutrophils in tissues (e.g., oral mucosa, skin and gastrointestinal tract) results in excessive interleukin-23 (IL-23) expression by macrophages leading to increased interleukin-17 (IL-17) and granulocyte-colony stimulating factor (G-CSF) levels. This evidence concerns the gene IL17A and Leukocyte adhesion deficiency type I.