HPS6 gene


Gene (OMIM No.)
Function of gene/protein
  • Protein: Subunit 3 of Biogenesis of lysosomal organelles complex 2 (BLOC-2)
  • Forms the BLOC-2 complex with HPS3 and HPS5
  • BLOC-2 complex plays a role in the biogenesis of lysosomes and lysosome-related organelles (LROs)
  • Lysosomes are cytoplasmic organelles that serve as a major degradative compartment in eukaryotes
  • LROs have similar features to lysosomes but have distinct morphology, composition and/or function
  • BLOC-2 controls the sorting and transport of proteins into LROs such as melanosomes and platelet dense granules during their formation
Clinical phenotype
(OMIM phenotype no.)
  • Hermansky-Pudlak syndrome 6 (#614075)
  • Autosomal recessive
Ocular features
  • Albinism
  • Intra- and interfamilial variability in disease severity
Systemic features
  • Skin and hair depigmentation
  • Bleeding diathesis due to platelet storage pool deficiency (easy/prolonged bleeding, easy bruising, prolonged/heavy menorrhagia, epistaxis)
Key investigations
  • Orthoptic assessment and refraction
  • OCT to detect foveal hypoplasia
  • Visual evoked potentials to detect evidence of chiasmal misrouting
  • Eye movement recordings
  • Systemic assessment with a pediatrician, haematologists and other relevant specialists
Molecular diagnosisNext generation sequencing
  • Targeted gene panels (albinism)
  • Whole exome sequencing
  • Whole genome sequencing
  • Multidisciplinary approach
Therapies under research
  • None in clinical trials at present
Further information

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  1.  Zhang Q, Zhao B, Li W, et al. Ru2 and Ru encode mouse orthologs of the genes mutated in human Hermansky-Pudlak syndrome types 5 and 6. Nat Genet. 2003;33(2):145-153
  2.  Schreyer-Shafir N, Huizing M, Anikster Y, et al. A new genetic isolate with a unique phenotype of syndromic oculocutaneous albinism: clinical, molecular, and cellular characteristics. Hum Mutat. 2006;27(11):1158
  3.  Huizing M, Pederson B, Hess RA, et al. Clinical and cellular characterisation of Hermansky-Pudlak syndrome type 6. J Med Genet. 2009;46(12):803-810
  4.  Miyamichi D, Asahina M, Nakajima J, et al. Novel HPS6 mutations identified by whole-exome sequencing in two Japanese sisters with suspected ocular albinism. J Hum Genet. 2016;61(9):839-842

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Updated on November 30, 2020
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