Hermansky–Pudlak Syndrome Type 6 Accompanied with Bowel Vascular Malformation: Clinical Case

Abstract

Background. Hermansky–Pudlak syndrome type 6 is rare hereditary disease caused by pathogenic variants in base sequence, deletions, and insertions in the HPS6 gene encoding the transmembrane protein of the same name. This disease occurs with hemorrhagic syndrome, oculocutaneous albinism, and inflammatory bowel diseases (in some cases). The clinical picture of the disease, including the gastrointestinal tract pathology, has not been studied completely due to the syndrome rarity.Clinical case description. We would like to present the description of clinical case of the patient with Hermansky–Pudlak syndrome type 6 accompanied with bowel vascular malformation. The patient diagnosed with “oculocutaneous albinism” at the age of 4.5 has shown recurrent intestinal bleedings, blood hemoglobin concentration decrease to 45 g/l; platelet count, mean platelet volume and platelet distribution width remained within the reference values. Slight decrease of Quick’s value to 68% (normal range 70–120%) was revealed. The study of platelet morphology has revealed a decrease in the number of dense granules: < 3 in 25% platelets, < 6 — in 64%. Ultrasound investigation has revealed signs of vascular malformation in ascending colon: significant changes of diameter (widening) and shape of intestinal wall vessels. Molecular genetic analysis (NGS) has revealed the nucleotide variant c.1133T>G (p.Leu378Arg) in homozygous state in the HPS6 gene. The same variant in homozygous state was revealed in the younger proband sister who also had vascular changes in the ascending colon wall.Conclusion. Differential diagnosis of Germanic–Pudlak syndrome type 6 should be performed with other types of this syndrome as well as with syndrome and non-syndrome forms of oculocutaneous albinism. Molecular genetic confirmation of the diagnosis is suggested via massive parallel sequencing (NGS) methods (exome sequencing included) due to the rarity of Hermansky–Pudlak syndrome.

Keywords

• hermansky–pudlak syndrome type 6
• oculocutaneous albinism
• platelets
• dense granules
• hemorrhagic syndrome
• bowel vascular malformation