For instance, HPS‐3, HPS‐5, and HPS‐6 have milder symptoms with respect to other HPS subtypes [120]; they do not develop the pulmonary fibrosis and granulomatous colitis that are seen in patients with defective BLOC‐3 (HPS1 and HPS4), or the neutropenia that is present in defective AP‐3 (HPS2 and HPS10). This evidence concerns the gene HPS4 and pulmonary fibrosis.