Novel mutation in Hermansky-Pudlak syndrome type 2 with mild immunological phenotype.

[oculocutaneous albinism]

Patients with Hermansky-Pudlak syndrome type 2 (HPS 2 ) present with oculocutaneous albinism , nystagmus , prolonged bleeding time , and increased susceptibility to infections . Twelve HPS 2 patients with mutations in the β 3 A-subunit of the cytosolic adaptor-related protein complex 3 (AP 3 B 1 , also called HPS 2 ) have been described so far . Here , we report on a patient with oculocutaneous albinism who developed a life-threatening bleeding after tonsillectomy . She presented with moderate neutropenia and reduced granulopoiesis . Analyzing patient 's impaired platelet function using electron microscopy and flow cytometry led to the diagnosis of HPS 2 . Flow cytometric analysis of the patient 's platelets showed already elevated CD 63 expression on resting platelets with no further increase after thrombin stimulation . Natural killer (NK ) cell degranulation was partially impaired but target cell lysis of NK cells and cytotoxic T -lymphocytes (CTLs ) were normal and the patient did not develop signs of hemophagocytic syndrome . Molecular genetic analyses revealed a novel 2 bp-deletion (c .3222 _3223 delTG ) in the last exon of AP 3 B 1 causing a frameshift and a prolonged altered protein . The location of the deletion at the very C-terminal end may prevent a complete loss of the HPS 2 protein leading to a less pronounced severity of immunodeficiency than in other HPS 2 patients .