Individuals with a BLOC-1 and BLOC-2 related mutations present with milder OCA symptoms, and little to no pulmonary fibrosis when compared to individuals with mutations in HPS1 and HPS4 (BLOC-3 related) (Iwata et al., 2000; Anikster et al., 2001). The gene discussed is HPS1; the disease is pulmonary fibrosis.