Dermatologic Manifestations of Hermansky-Pudlak Syndrome Workup

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

Laboratory Studies

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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Imaging Studies

High-resolution CT is more sensitive than chest radiography in evaluating the extent of pulmonary disease in patients with Hermansky-Pudlak syndrome. [37] Mild findings on high-resolution CT scans are paralleled by normal findings on chest radiographs. Common chest radiographic findings include reticulonodular interstitial pattern, perihilar fibrosis, and pleural thickening. High-resolution CT scans can show septal thickening, ground-glass opacities, and peribronchovascular thickening. One study noted that 82% of patients with Hermansky-Pudlak syndrome had abnormalities on high-resolution CT scans. [38]

Owing to the increase risk of bleeding complications, patients with Hermansky-Pudlak syndrome who experience physical trauma should undergo CT scanning to rule out intra-articular, intracranial, and/or internal bleeding.

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Other Tests

Vision should be tested and evaluated in a comprehensive fashion. Inspecting the iris for transillumination and the retina for findings compatible with albinism is useful, as is visual-acuity testing. In children with Hermansky-Pudlak syndrome, it is important to consider that impaired vision may affect their ability to learn. Therefore, educational and intellectual testing should be performed.

Patients with Hermansky-Pudlak syndrome should be evaluated by 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 decrease as interstitial lung disease progresses.

Some studies have reported that patients with albinism have a decreased bone density when compared with age-corrected control subjects, but the role of testing for bone density is unclear in Hermansky-Pudlak syndrome.

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Procedures

Skin biopsy should be performed immediately on new skin lesions to evaluate for skin cancer.

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Histologic Findings

Histologic and ultrastructural findings of non–sun-exposed skin showed melanocytes, with short dendritic processes and decreased numbers of melanosomes. Ultrastructural examination of platelets revealed greatly reduced numbers of delta granules. In adults, solar elastosis is usually present on sun-exposed skin.

Izquierdo et al [39] found that patients with HPS-1 have thicker foveae than normal controls, perhaps because of the absence of a foveal pit as part of the foveal hypoplasia associated with Hermansky-Pudlak syndrome. Conversely, persons with Hermansky-Pudlak syndrome have lower macular volumes compared with the general population, perhaps because of a loss of retinal nuclear layers in these patients.

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