Hermansky-Pudlak Syndrome Workup

Updated: Jul 28, 2020
  • Author: Ahmed Farghaly Abdelhameed Omar, MD, PhD; Chief Editor: Hampton Roy, Sr, MD  more...
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Laboratory Studies

The most accurate test for the diagnosis of HPS is platelet electron microscopy. [21] Platelets of individuals with the syndrome show virtual absence of DB. The high calcium content of DB allows their visualization in unfixed, unstained whole mount preparations in the EM. DB are needed for the second phase of platelet aggregation. HPS platelets lack granulophysin/CD63, which is a DB component and lysosomal membrane marker.

Genetic linkage analysis: Patients with OCA and bleeding tendencies may be referred for genetic linkage analysis, which may identify the causative mutation. [22] Genetic testing is recommended to determine the specific subtype in patients with HPS, as this can alter follow-up needs and prognosis. [21]

Hair bulb incubation test classifies patients with OCA into tyrosinase negative or tyrosinase positive. All patients with Hermansky-Pudlak syndrome (HPS) have Ty-pos OCA. Test results should be correlated clinically because some patients may have false-negative results. This test was the standard in the 1990s. Bleeding time of patients with the syndrome varies from 6-20 minutes. Witkop and co-workers reported that 25% of patients with the syndrome have bleeding time within normal limits. [9]

Neither prothrombin time (PT) nor activated partial thromboplastin (aPTT) changes in patients with the syndrome. Routine blood smear findings are likely to be normal in these patients.

Platelet studies: Patients with the syndrome have normal platelets counts. However, platelets in patients with the syndrome show abnormal aggregation with collagen, thrombin, epinephrine, and ADP.

Desmopressin trial: Some patients with the syndrome have an improved platelet aggregation, upon intravenous or intramuscular desmopressin injection. Patient's response to desmopressin should be evaluated prior to elective surgical procedures.

Pulmonary function tests: Mutations in the HPS-1 gene are associated with fatal pulmonary fibrosis. [23] Patients with HPS should be evaluated using pulmonary function tests. Forced vital capacity (FVC), forced expiratory volume (FEV), mean total lung capacity, mean vital capacity, and mean diffusing capacity of the lung for carbon monoxide fall as interstitial lung disease progresses in patients with the syndrome.

Bone densitometry: Previous studies have reported that patients with albinism have a decreased bone density when compared to age-corrected control subjects. Bone densitometry is advisable in patients with OCA.


Imaging Studies

High-resolution CT (HRCT) chest scan may be requested by a pulmonologist in patients with the syndrome. Brantly and coworkers report that 82% of patients with the syndrome have abnormal HRCT chest scans. [24] Lung biopsy is not necessary for diagnosis of HPS and is contraindicated because of the potential for bleeding complications. [21]

Patients with the syndrome who undergo trauma should have a CT scan to rule out intra-articular or intracranial bleeding.


Other Tests

Low vision aids

Since patients with the syndrome have low vision, patients may benefit from a low vision aid evaluation. Instruments, such as closed circuit television (CCTV), "traveler's device," scanners, and telescopic lenses, facilitate patients' learning process.

Intelligence tests

Since patients with the syndrome have low vision, special (for the visually handicapped) intelligence quotient tests should be used to evaluate them.


Histologic Findings

Histologic examination of lung tissue from patients with HPS pulmonary fibrosis demonstrates findings similar to those of idiopathic pulmonary fibrosis. Furthermore, foamy swelling of epithelial cells and alveolar macrophages can be seen. [21, 25, 26]