What is the role of lab tests in the workup of Hermansky-Pudlak syndrome (HPS)?

Updated: Dec 13, 2019
  • Author: Jaclyn Scholtz, MD; Chief Editor: Dirk M Elston, MD  more...
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Answer

Genetic testing for the HPS1 gene, which most commonly occurs in Puerto Ricans, exists. A company called GeneDx can perform DNA screening for the 16–base pair duplication found in this variation of Hermansky-Pudlak syndrome (HPS).

Examination of blood platelets under an electron microscope can be performed. The absence of dense granules in the platelets is characteristic of this syndrome. The ultrastructure of ceroid-lipofuscin inclusions in macrophages in bone marrow, gut, and other tissues can be helpful, but the absence of dense granules in the platelets in association with albinism is diagnostic for Hermansky-Pudlak syndrome.

Standard blood tests (eg, prothrombin time [PT], activated partial thromboplastin time [aPTT], platelet count, bleeding time) do not identify the platelet defect in Hermansky-Pudlak syndrome. Bleeding time of patients with Hermansky-Pudlak syndrome varies from 6-20 minutes. As many as 25% of patients with Hermansky-Pudlak syndrome have bleeding times within the normal reference range. Many patients with Hermansky-Pudlak syndrome have reduced von Willebrand factor activity in their platelets. There are some reports that these patients lack the CD63 marker on platelets.

Hair bulb incubation test can be used to classify patients with albinism into tyrosinase negative or tyrosinase positive. All patients with Hermansky-Pudlak syndrome have tyrosine-positive albinism. Clinical correlation is necessary because some patients with Hermansky-Pudlak syndrome may have false-negative results.


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