HPS3 gene


Gene (OMIM No.)
Function of gene/protein
  • Protein: Subunit 1 of the biogenesis of lysosomal-related organelles complex 2 (BLOC-2)
  • Forms the BLOC-2 complex with HPS5 and HPS6
  • 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 3 (#614072)
  • 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.  Anikster Y, Huizing M, White J, et al. Mutation of a new gene causes a unique form of Hermansky-Pudlak syndrome in a genetic isolate of central Puerto Rico. Nat Genet. 2001;28(4):376-380
  2.  Huizing M, Anikster Y, Fitzpatrick DL, et al. Hermansky-Pudlak syndrome type 3 in Ashkenazi Jews and other non-Puerto Rican patients with hypopigmentation and platelet storage-pool deficiency. Am J Hum Genet. 2001;69(5):1022-1032

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Updated on November 30, 2020
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