Hermansky-Pudlak syndrome in a Swiss population

A novel likely pathogenic variant in a patient with Hermansky-Pudlak syndrome

Hermansky-Pudlak syndrome (HPS) is a genetic disorder characterized by oculocutaneous albinism and variable pulmonary fibrosis, granulomatous colitis, or immunodeficiency. The diagnosis relies on clinical findings, platelet transmission electron microscopy studies showing absent dense granules, or the identification of a pathogenic genotype in one of 11 associated genes, including HPS1 We report a 2-wk-old male with significant iris transillumination defects, a pale fundus, and mild corectopia found by clinical exome sequencing to have a previously reported pathogenic variant, c.972dupC p.(Met325HisfsTer128), and a variant of uncertain significance, c.1846G>A p.(Glu616Lys), in HPS1 To determine whether his phenotype was consistent with HPS, follow-up studies of whole blood lumiaggregometry and platelet transmission electron microscopy were performed that revealed absent or markedly reduced platelet ATP secretion and virtually absent platelet dense granules, thus confirming the diagnosis. To the best of our knowledge, our case is the first in which the c.1846G>A p.(Glu616Lys) variant is identified in a patient with HPS. In addition, the case also highlights the importance of leveraging appropriate confirmatory clinical testing and reverse phenotyping, which allowed the care team to establish the clinical diagnosis of HPS and reclassify the previously reported variant of uncertain significance in HPS1 to likely pathogenic.

Hermansky-Pudlak syndrome pulmonary fibrosis: a rare inherited interstitial lung disease

Pulmonary fibrosis is a progressive interstitial lung disease of unknown aetiology with a poor prognosis. Studying genetic diseases associated with pulmonary fibrosis provides insights into the pathogenesis of the disease. Hermansky-Pudlak syndrome (HPS), a rare autosomal recessive disorder characterised by abnormal biogenesis of lysosome-related organelles, manifests with oculocutaneous albinism and excessive bleeding of variable severity. Pulmonary fibrosis is highly prevalent in three out of 10 genetic types of HPS (HPS-1, HPS-2 and HPS-4). Thus, genotyping of individuals with HPS is clinically relevant. HPS-1 tends to affect Puerto Rican individuals due to a genetic founder effect. HPS pulmonary fibrosis shares some clinical features with idiopathic pulmonary fibrosis (IPF), including dyspnoea, cough, restrictive lung physiology and computed tomography (CT) findings of fibrosis. In contrast to IPF, HPS pulmonary fibrosis generally affects children (HPS-2) or middle-aged adults (HPS-1 or HPS-4) and may be associated with ground-glass opacification in CT scans. Histopathology of HPS pulmonary fibrosis, and not IPF, shows vacuolated hyperplastic type II cells with enlarged lamellar bodies and alveolar macrophages with lipofuscin-like deposits. Antifibrotic drugs approved as treatment for IPF are not approved for HPS pulmonary fibrosis. However, lung transplantation has been performed in patients with severe HPS pulmonary fibrosis. HPS pulmonary fibrosis serves as a model for studying fibrotic lung disease and fibrosis in general.

Hermansky-Pudlak syndrome: Mutation update

Hermansky-Pudlak syndrome (HPS) is a group of 10 autosomal recessive multisystem disorders, each defined by the deficiency of a specific gene. HPS-associated genes encode components of four ubiquitously expressed protein complexes: Adaptor protein-3 (AP-3) and biogenesis of lysosome-related organelles complex-1 (BLOC-1) through -3. All individuals with HPS exhibit albinism and a bleeding diathesis; additional features occur depending on the defective protein complex. Pulmonary fibrosis is associated with AP-3 and BLOC-3 deficiency, immunodeficiency with AP-3 defects, and gastrointestinal symptoms are more prevalent and severe in BLOC-3 deficiency. Therefore, identification of the HPS subtype is valuable for prognosis, clinical management, and treatment options. The prevalence of HPS is estimated at 1-9 per 1,000,000. Here we summarize 264 reported and novel variants in 10 HPS genes and estimate that ~333 Puerto Rican HPS subjects and ~385 with other ethnicities are reported to date. We provide pathogenicity predictions for missense and splice site variants and list variants with high minor allele frequencies. Current cellular and clinical aspects of HPS are also summarized. This review can serve as a manifest for molecular diagnostics and genetic counseling aspects of HPS.

Genetic variants associated with Hermansky-Pudlak syndrome

Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive disorder characterized by defective biogenesis of lysosome-related organelles. Clinical manifestations include a bleeding diathesis due to a platelet delta storage pool deficiency, oculocutaneous albinism, inflammatory bowel disease, neutropenia, and pulmonary fibrosis. Ten genes associated with HPS are identified to date, and each gene encodes a protein subunit of either Biogenesis of Lysosome-related Organelles Complex (BLOC)-1, BLOC-2, BLOC-3, or the Adaptor Protein-3 complex. Several genetic variants and phenotypic heterogeneities are reported in individuals with HPS, who generally exhibit easy bruisability and increased bleeding. Desmopressin, pro-coagulants, or platelet transfusion may be used as prophylaxis or treatment for excessive bleeding in patients with HPS. However, response to desmopressin can be variable. Platelets are effective in preventing or treating bleeding in individuals with HPS, but platelets should be transfused judiciously to limit alloimmunization in patients with HPS who are at risk of developing pulmonary fibrosis and may be potential candidates for lung transplantation. The discovery of new genes associated with HPS in people with excessive bleeding and hypopigmentation of unknown etiology may be facilitated by the use of next-generation sequencing or panel-based genetic testing.

Angeborene Thrombozytenfunktionsstörungen

Angeborene Thrombozytopathien können zu Blutungssymptomen unterschiedlichen Schweregrades führen, da die Thrombozyten nicht mehr ihre Funktion nach einer Gefäß-verletzung erfüllen können. In manchen Fällen sind Thrombozytopathien schwierig zu diagnostizieren und können Probleme in der Therapie und im Management verursachen. Dieser Review beschreibt den klinischen und molekulargenetischen Phänotyp der verschiedenen angeborenen Thrombozytopathien. Die angeborenen Thrombozytopathien werden entsprechend des Thrombozytendefekts eingeteilt: Rezeptordefekte (Adhäsion oder Aggregation), Sekretionsdefekte und Zytoskelettdefekte.

Die am besten charakterisierten thrombozytären Rezeptordefekte sind die Glanzmann Thrombasthenie (Defekt des Integrins [uni03B1]IIb[uni03B2]3) und das Bernard-Soulier Syndrom (Defekt des GPIb/IX/V Rezeptors). Umfassende Fall-berichte über die Blutungsdiathese sowie die Untersuchung der Thrombozytenaggregation bzw. -agglutination und Rezeptorexpression von Patienten, die an der Glanzmann Thrombasthenie (GT) oder am Bernard-Soulier Syndrom (BSS) leiden, sollen diesen Review ergänzen. Darüber hinaus wird das HermanskyPudlak Syndrom (HPS) als eine bedeutende Störung der [uni03B4]-Granula Sekretion zusammen mit einer Fallbeschreibung eines Patienten, der an HPS Typ 1 leidet, beschrieben.

Hypertension, chronic kidney disease, and renal pathology in a child with hermansky-pudlak syndrome

We report a child with Hermansky-Pudlak Syndrome (HPS) and chronic kidney disease (stage II) with histological diagnosis of focal segmental glomerulosclerosis (FSGS). A 15-year-old male of Puerto Rico ancestry with history of HPS, hypertension (HTN), asthma, obesity, and chronic kidney disease (CKD) stage II presented with new-onset proteinuria without edema. His blood pressure had been controlled, serum creatinine had been 0.9-1.4 mg/dL, and first morning urine protein/creatinine ratio (UPC) ranged from 0.2 to 0.38. Due to persistent nonorthostatic proteinuria with CKD, renal biopsy was performed and FSGS (not otherwise specified) with chronic diffuse tubulopathy (tubular cytoplasmic droplets) and acute tubular injury was reported. Ceroid-like material is known to infiltrate tissues (i.e., lungs, colon, and kidney) in HPS, but the reason for the renal insufficiency is unknown. Nonspecific kidney disease and in one adult case IgA nephropathy with ANCA-positive glomerulonephritis have previously been reported in patients with Hermansky-Pudlak syndrome. To our knowledge, we report the first pediatric renal pathology case of HPS associated with CKD. This paper discusses presentation and management of renal disease in HPS.

Current Strategies in Diagnosis of Inherited Storage Pool Defects

Inherited platelet defects lead to bleeding symptoms of varying severity. Typically, easy bruising, petechiae, epistaxis, and mucocutaneous bleeding are observed in affected patients. The platelet defects are classified into disorders affecting either platelet surface receptors or intracellular organelles of platelets. The latter are represented by platelet storage pool diseases (SPD) which share a defect of platelet granules. Platelet α-granules, δ-granules, or both may be affected resulting in the clinical picture of α-SPD (e.g. Gray platelet syndrome, Quebec platelet disorder, arthrogryposis, renal dysfunction, and cholestasis syndrome), δ-SPD (e.g. Hermansky-Pudlak syndrome, Chediak-Higashi syndrome, Griscelli syndrome), or αδ-SPD (e.g. X-linked thrombocytopenia, Wiskott-Aldrich syndrome). Diagnosis of SPD is very extensive and requires platelet aggregation and flow cytometry analyses with interpretation from a specialist. Many of these disorders share common treatments, however, efficacy can vary between different patients. Therapy regiments with tranexamic acid, DDAVP, activated FVIIa, and platelet transfusions have been published. Stem cell or bone marrow transplantations are preserved for severe defects. Here, we describe the pathophysiology, clinical manifestations, and diagnosis of the major human SPDs.

Hermansky-Pudlak syndrome in two African-American brothers

Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder characterized by oculocutaneous albinism, a bleeding disorder, and, in some patients, granulomatous colitis and/or a fatal pulmonary fibrosis. There are eight different subtypes of HPS, each due to mutations in one of eight different genes, whose functions are thought to involve intracellular vesicle formation and trafficking. HPS has been identified in patients of nearly all ethnic groups, though it has primarily been associated with patients of Puerto Rican, Northern European, Japanese and Israeli descent. We report on the diagnosis of HPS type 1 in two African-American patients. Both brothers carried compound heterozygous mutations in HPS1: previously reported p.M325WfsX6 (c.972delC) and a novel silent mutation p.E169E (c.507G > A), which resulted in a splice defect. HPS may be under-diagnosed in African-American patients and other ethnic groups. A history of easy bruising or evidence of a bleeding disorder, combined with some degree of hypopigmentation, should prompt investigation into the diagnosis of HPS.

Focus on mammalian thioredoxin reductases--important selenoproteins with versatile functions

Thioredoxin systems, involving redox active thioredoxins and thioredoxin reductases, sustain a number of important thioredoxin-dependent pathways. These redox active proteins support several processes crucial for cell function, cell proliferation, antioxidant defense and redox-regulated signaling cascades. Mammalian thioredoxin reductases are selenium-containing flavoprotein oxidoreductases, dependent upon a selenocysteine residue for reduction of the active site disulfide in thioredoxins. Their activity is required for normal thioredoxin function. The mammalian thioredoxin reductases also display surprisingly multifaceted properties and functions beyond thioredoxin reduction. Expressed from three separate genes (in human named TXNRD1, TXNRD2 and TXNRD3), the thioredoxin reductases can each reduce a number of different types of substrates in different cellular compartments. Their expression patterns involve intriguingly complex transcriptional mechanisms resulting in several splice variants, encoding a number of protein variants likely to have specialized functions in a cell- and tissue-type restricted manner. The thioredoxin reductases are also targeted by a number of drugs and compounds having an impact on cell function and promoting oxidative stress, some of which are used in treatment of rheumatoid arthritis, cancer or other diseases. However, potential specific or essential roles for different forms of human or mouse thioredoxin reductases in health or disease are still rather unclear, although it is known that at least the murine Txnrd1 and Txnrd2 genes are essential for normal development during embryogenesis. This review is a survey of current knowledge of mammalian thioredoxin reductase function and expression, with a focus on human and mouse and a discussion of the striking complexity of these proteins. Several yet open questions regarding their regulation and roles in different cells or tissues are emphasized. It is concluded that the intriguingly complex regulation and function of mammalian thioredoxin reductases within the cellular context and in intact mammals strongly suggests that their functions are highly fi ne-tuned with the many pathways involving thioredoxins and thioredoxin-related proteins. These selenoproteins furthermore propagate many functions beyond a reduction of thioredoxins. Aberrant regulation of thioredoxin reductases, or a particular dependence upon these enzymes in diseased cells, may underlie their presumed therapeutic importance as enzymatic targets using electrophilic drugs. These reductases are also likely to mediate several of the effects on health and disease that are linked to different levels of nutritional selenium intake. The thioredoxin reductases and their splice variants may be pivotal components of diverse cellular signaling pathways, having importance in several redox-related aspects of health and disease. Clearly, a detailed understanding of mammalian thioredoxin reductases is necessary for a full comprehension of the thioredoxin system and of selenium dependent processes in mammals.

Hermansky-Pudlak syndrome: a disease of protein trafficking and organelle function

The Hermansky-Pudlak syndrome (HPS) is a collection of related autosomal recessive disorders which are genetically heterogeneous. There are eight human HPS subtypes, characterized by oculocutaneous albinism and platelet storage disease; prolonged bleeding, congenital neutropenia, pulmonary fibrosis, and granulomatous colitis can also occur. HPS is caused primarily by defects in intracellular protein trafficking that result in the dysfunction of intracellular organelles known as lysosome-related organelles. HPS gene products are all ubiquitously expressed and all associate in various multi-protein complexes, yet HPS has cell type-specific disease expression. Impairment of specialized secretory cells such as melanocytes, platelets, lung alveolar type II epithelial cells and cytotoxic T cells are observed in HPS. This review summarizes recent molecular, biochemical and cell biological analyses together with clinical studies that have led to the correlation of molecular pathology with clinical manifestations and led to insights into such diverse disease processes such as albinism, fibrosis, hemorrhage, and congenital neutropenia.

Pulmonary fibrosis in hermansky-pudlak syndrome. a case report and review

Hermansky-Pudlak syndrome (HPS) is a rare heterogeneously inherited autosomal recessive group of disorders presenting with oculocutaneous albinism, bleeding diathesis and pulmonary disease. HPS is thought to occur as a consequence of disturbed formation or trafficking of intracellular vesicles, most importantly, melanosomes, platelet dense granules and lysosomes. The latter finding, in particular, contributes much to the morbidity associated with the disease, as ceroid lipofuscin deposits in lysosomes affect many organ systems. This is especially problematic in the lungs where it is often associated with pulmonary fibrosis and premature death. Currently, there are 7 known HPS genes in humans. In the mouse, at least 16 known HPS genes produce HPS-mutant phenotypes. The HPS gene mutation is considered to be one of the most prevalent single-gene disorders in northwest Puerto Rico, home to the largest cohort of known patients. In HPS, interventions addressing the bleeding diathesis and pulmonary fibrosis are often disappointingly ineffectual. Pirfenidone, a novel compound with documented anti-inflammatory, antioxidant and antifibrotic effects, appears to hold promise in delaying or preventing fibrosis. To date, there has been one successful lung transplant performed on a patient with HPS. We present a patient with HPS and review the current literature on our understanding of this rare disorder.

Hermansky-Pudlak syndrome with a novel mutation

We report a case of Hermansky-Pudlak syndrome (HPS) with a novel mutation in the HPS1 gene. This case showed oculocutaneous albinism and lysosomal ceroid accumulation, however platelet dysfunction was not observed. Histopathological findings of the biopsied lung tissue were compatible with HPS. Sequencing analysis showed the insertion of C in the codon 178 (739 bp) of the HPS1 gene forming a stop codon at codon 181. To the best of our knowledge, this is a novel HPS1 gene mutation.

Ultrastructural Features of Trafficking Defects Are Pronounced in Melanocytic Nevus in Hermansky–Pudlak Syndrome Type 1

Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder characterized by oculocutaneous albinism, a bleeding disorder, and ceroid lipofuscinosis in the lungs and gut. HPS is genetically heterogeneous and the most common variant, HPS type 1, is caused by mutations in HPS1 gene. The protein encoded by HPS1 is considered to facilitate the trafficking of melanocyte-specific gene products into the premelanosome. We report the ultrastructural findings in a melanocytic nevus seen in a 17-y-old Japanese female patient with HPS1 who is a compound heterozygote of HPS1 mutations, including a novel mutation. Electron microscopy of a pinkish papule corresponding to the melanocytic nevus revealed markedly aberrant, immature melanosomes, large membranous structures, and giant melanosomes in the vicinity of trans-Golgi network, the characteristic abnormalities because of protein trafficking defects in HPS1. These ultrastructural features were far more clearly demonstrated in the nevus cells than in the epidermal melanocytes. Thus, ultrastructural analysis of nevus cells may be an additional diagnostic tool for HPS1 and could give us important clues to further understanding of the pathomechanisms of HPS.

Hermansky-Pudlak syndrome with interstitial pneumonia without mutation of HSP1 gene

A 57-year-old man with occulocutaneous albinism was admitted to our hospital because of exertional dyspnea and an abnormal shadow on chest roentgenogram. Chest CT revealed diffuse interstitial shadows with reticulonodular opacities in the bilateral whole lung fields and his pulmonary function test was consistent with a restrictive finding. Histologically, intraluminal diffuse fibrosis and interstitial fibrosis existed and ceroid-like materials within alveolar macrophages were demonstrated in a transbronchial lung biopsy specimen. In addition, because platelet dysfunction and ceroid-like materials within the reticuloendothelial cells of urine and bone marrow aspiration were recognized, we made a diagnosis of Hermansky-Pudlak syndrome (HPS). Gene analysis of the patient's peripheral blood cells did not reveal that he was a compound homogeneity for HPS1 gene mutations. Concerning treatment, although corticosteroid therapy was administered, his clinical symptoms and abnormal chest shadow have not changed.

Hermansky-Pudlak syndrome type 4 in a patient from Sri Lanka with pulmonary fibrosis

Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive disorder characterized by oculocutaneous albinism and a platelet storage pool deficiency. Some patients also develop fatal pulmonary fibrosis and some have granulomatous colitis. Six human genes HPS1, ADB3A, HPS3, HPS4, HPS5, and HPS6 have been identified as cause of the six known subtypes of HPS. While there exist nearly 500 Puerto Rican and non-Puerto Rican HPS-1 patients, very few HPS-4 patients have been reported, and most of these have not been described in detail. We now delineate the clinical characteristics of an HPS-4 patient homozygous for a novel HPS-4 mutation, P685delC. The patient, the first individual with HPS reported from Sri Lanka, had severe pulmonary fibrosis, typical of HPS-1 disease, without granulomatous colitis. We conclude that pulmonary fibrosis occurs as part of HPS-4 and that HPS should be considered in all ethnic groups.

Pigmentary disorders in ethnic skin

Pigmentary disorders are commonly seen in ethnic skin. They are psychologically problematic in darker skin. Treatment of many of these disorders remains difficult.

Pulmonary pathologies in pallid mice result from nonhematopoietic defects

Several single gene pigment mutants of inbred C57BL/6J mice display a triad of subcellular granule-associated defects: oculocutaneous pigment dilution, prolonged bleeding due to defects in platelet dense granules, and abnormal lysosomes. These features also characterize Hermansky-Pudlak Syndrome (HPS), making these mice relevant animal models for HPS. Mice of one mutant strain, pallid, in addition to the hallmark triad of signs, also exhibit age-dependent lung pathology. Respiratory system mechanics showed that the age-dependent histopathology of pallid mice was accompanied by a decrease in lung reactance. Furthermore, the possibility that pallid pulmonary pathology may result from persistent inflammation due to microhemorrhage owing to the platelet defect was examined. Hematopoietic reconstitution of pallid mice with marrow from normal C57BL/6J donors did not prevent the development of the pulmonary histopathology or respiratory system mechanics characteristic of the pallid genotype. Similarly, wild-type mice 12 months after engraftment with pallid marrow did not develop pallid-like pulmonary histopathology or respiratory system mechanics. Thus, pallid-associated pulmonary functional and structural pathologies are not linked to the marrow (bleeding) genotype, but instead are the result of an age-dependent process resulting from a defect(s) in one or more nonhematopoietic cell types.

Hermansky-Pudlak syndrome: infrequent bleeding and first report of Turkish and Pakistani kindreds

Hermansky-Pudlak syndrome (HPS) is a rare disorder characterised by oculocutaneous albinism, a bleeding tendency, and lipofuscinosis. This retrospective study reviews the clinical history and haematological features of 23 cases of HPS. Information was gathered from patient notes and by direct interview. Thirteen of the 23 children were of Turkish origin, 12 being members of four kindreds from the Turkish/Kurdish border. Four children originated from Pakistan. Haemorrhage was uncommon; two experienced significant bleeding (intracranial and retinal haemorrhage in one and menorrhagia in another), and twelve minor symptoms. Results of laboratory evaluation of platelet function were not predictive of bleeding; in particular the PFA-100 analyser was not sensitive to the HPS defect. The most sensitive test of platelet fuction was quantitation of platelet nucleotides. The occurrence of Turkish and Pakistani kindreds with HPS is novel and follow up for long term complications described in Puerto Rican patients as well as genetic analysis is ongoing.

Heterozygous HPS1 mutations in a case of Hermansky-Pudlak syndrome with giant melanosomes

We report a Japanese man with Hermansky-Pudlak syndrome, having oculocutaneous albinism with a bleeding diathesis. Gene analysis of the patient's peripheral blood cells revealed that he was a compound heterozygote for HPS1 gene mutations. One of the mutations was a novel frameshift mutation at codon 321 (a G insertion) in exon 11 ( approximately 962-963insG), and the other was a 5' splice-junction mutation of IVS5 (IVS5 + 5G-->A). The content of eumelanin in the patient's hairs was significantly reduced. Histological analysis using light and electron microscopy revealed that melanocytes in the patient's epidermis contained an appreciable number of giant melanosomes. Cultured melanocytes from the patient's skin also contained giant melanosomes. Our finding of mutations in the HPS1 gene in relation to abnormalities in melanosome morphology and melanin production shed light on the role and function of the HPS1 gene product in the synthesis of melanosomes and melanin pigment.

Coagulation and Bleeding Disorders: Review and Update

Hemostasis is initiated by injury to the vascular wall, leading to the deposition of platelets adhering to components of the subendothelium. Platelet adhesion requires the presence of von Willebrand factor and platelet receptors (IIb/IIIa and Ib/IX). Additional platelets are recruited to the site of injury by release of platelet granular contents, including ADP. The “platelet plug” is stabilized by interaction with fibrinogen. In this review, I consider laboratory tests used to evaluate coagulation, including prothrombin time, activated partial thromboplastin time, thrombin time, and platelet count. I discuss hereditary disorders of platelets and/or coagulation proteins that lead to clinical bleeding as well as acquired disorders, including disseminated intravascular coagulation and acquired circulating anticoagulants.

Correlation of visual acuity and ocular pigmentation with the 16-bp duplication in the HPS-1 gene of Hermansky-Pudlak syndrome, a form of albinism

OBJECTIVE

Patients with the Hermansky-Pudlak syndrome (HPS), a form of albinism, were studied. The first purpose of this investigation was to determine if visual acuity was related to the presence or absence of the 16-bp duplication in the HPS-1 gene. The second was to study the correlation between the degree of ocular pigmentation and visual acuity within the two genetic groups described above.

DESIGN

Cross-sectional study of a series of consecutive patients.

PARTICIPANTS

Forty-nine patients with HPS with or without the 16-bp duplication in HPS-1.

METHODS

Best corrected visual acuity (VA) using Early Treatment Diabetic Retinopathy Study (ETDRS) charts, photographic gradings of iris transillumination and of visibility of choroidal vessels in the macula (macular transparency).

MAIN OUTCOME MEASURES

Association between VA and the presence or absence of the 16-bp duplication in HPS-1 and correlation between VA and the degree of iris transillumination (iris score) and macular transparency (fundus score), as determined by masked reading of photographs, with respect to the presence or absence of the 16-bp duplication in HPS-1 were the main outcome measures.

RESULTS

The VA of the better eye did not differ between the two genetic groups (P = 0.322, two-sided t test). Spearman's rank correlation between VA and iris scores in 39 eyes of 20 patients with the duplication was not statistically significant (P = 0.698) but was statistically significant in 36 eyes of 19 patients without the duplication (P < 0.001). Among all patients, the correlation was statistically significant (r = -0.36 in RE and r = -0.51 in LE). Spearman's rank correlation between VA and fundus scores in 36 eyes of 19 patients with and 34 eyes in 18 patients with and without the duplication was statistically significant (P = 0.035 and P = 0.008, respectively). Among all patients, it was also statistically significant (r = -0.39 in RE and r = -0.45 in LE).

CONCLUSIONS

The mean VA of the better eye did not differ in patients with the 16-bp duplication compared with those without the duplication. There were statistically significant associations between VA and the iris score and the fundus score except for the VA and iris scores in patients with the 16-bp duplication. However, because of the variability of VA, these associations were not large enough for useful prediction of VA based on the degree of ocular pigmentation.

Platelet von Willebrand factor in Hermansky-Pudlak syndrome

The Hermansky-Pudlak Syndrome (HPS) is an autosomal recessive inherited disorder characterized by oculocutaneous albinism, tissue accumulation of ceroid pigment, and a mild to moderate bleeding diathesis attributed to storage-pool deficient (SPD) platlets. Patients have platelet aggregation and release abnormalities. In addition, low levels of plasma von Willebrand factor (vWF) antigen in some HPS patients have been associated with a greater bleeding tendency than would be predicted from either condition alone. Other HPS patients have severe bleeding despite normal levels of plasma vWF, suggesting that at least one additional factor is responsible for their bleeding diathesis. Because platelet vWF levels have been well correlated with clinical bleeding times in patients with von Willebrand's disease, we have measured the platelet vWF activity and antigen levels in 30 HPS patients and have attempted to correlate their clinical bleeding with these values. The platelet vWF activity levels in patients was significantly lower than that of normal subjects (P < 0.0001). The patients as a group also had slightly lower values of plasma vWF activity when compared with normals (P-0.03). In 11 of the HPS patients, the multimeric structure of plasma vWF showed a decrease in the high molecular weight multimers and an increase in the low molecular weight multimers. In correlating the platelet and plasma vWF values with the bleeding histories, we were not able to show a predictable relationship in the majority of the patients.

Perturbed epidermal pterin metabolism in Hermansky-Pudlak syndrome

In Hermansky-Pudlak Syndrome (HPS) a mutation in a 79.3 kDa transmembrane protein has been shown. The function of this protein has escaped definition so far. This study unveils a defective (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin (6BH4) de novo synthesis/recycling for this cofactor in HPS, where activities of the key enzyme GTP-cyclohydrolase I are in the normal range, but total biopterin levels are significantly decreased in homozygotes (n = 5) compared with unaffected controls (n = 4) (p = 0.00001). Phenylalanine hydroxylase and 4a-hydroxy-6BH4-dehydratase activities are significantly lower. mRNA of all enzymes involved in 6BH4 biosynthesis/recycling and GTP-cyclohydrolase I feedback regulatory protein were expressed in keratinocytes from homozygotes, heterozygotes, and healthy controls. Thioredoxin/thioredoxin reductase can directly control the redox status of 6BH4. These activities are allosterically controlled by calcium. Therefore calcium would directly affect this redox status. In HPS these enzyme activities are low concomitant with a defective calcium uptake, suggesting an extracellular accumulation of this second messenger. In this context phenylalanine hydroxylase is subject to phosphorylation/activation by calcium/calmodulin activated kinases. Therefore it was anticipated that calcium could directly affect the cellular L-phenylalanine turnover to L-tyrosine. A significantly more rapid L-phenylalanine uptake and its turnover to L-tyrosine was identified in normal human melanocytes (n = 5) and keratinocytes (n = 2), and was more enhanced in melanocytes in the presence of 2 x 10(-3) M calcium. The turnover to L-tyrosine was significantly slower. Based on all evidence to date, we speculate that the mutated protein in HPS could be primarily involved in maintaining calcium homeostasis in this patient group.

Three new mutations in a gene causing Hermansky-Pudlak syndrome: clinical correlations

Hermansky-Pudlak syndrome (HPS) consists of oculocutaneous albinism, a platelet storage pool deficiency, and ceroid lipofuscinosis. HPS is common in northwest Puerto Rico, where affected individuals are homozygous for a 16-bp duplication in the gene HPS. Two other homozygous frameshift mutations in HPS were previously identified among non-Puerto Rican patients. Eighteen non-Puerto Rican HPS families were studied and HPS mutations in three of them identified. One mutation, T322insC, has been previously described. However, three additional mutations, E133X, T322delC, and S396delC, have not been reported. Two families exhibited compound heterozygosity for these mutations, although most previously reported HPS patients have been homozygous for a particular mutation. All the newly described mutations were associated with decreased or undetectable levels of HPS RNA by Northern blot analysis of fibroblasts, and all had significant pigment dilution. To date, all mutations in HPS result in a truncated protein, suggesting that the C-terminal portion of the HPS protein is functionally important.

Genetic defects and clinical characteristics of patients with a form of oculocutaneous albinism (Hermansky-Pudlak syndrome)

BACKGROUND

Hermansky-Pudlak syndrome is characterized by oculocutaneous albinism, a storage-pool deficiency, and lysosomal accumulation of ceroid lipofuscin, which causes pulmonary fibrosis and granulomatous colitis in some cases. All identified affected patients in northwest Puerto Rico are homozygous for a 16-bp duplication in exon 15 of a recently cloned gene, HPS. We compared the clinical and laboratory characteristics of these patients with those of patients without the 16-bp duplication.

METHODS

Forty-nine patients -- 27 Puerto Ricans and 22 patients from the mainland United States who were not of Puerto Rican descent -- were given a diagnosis on the basis of albinism and the absence of platelet dense bodies. We used the polymerase chain reaction to determine which patients carried the 16-bp duplication.

RESULTS

Twenty-five of the Puerto Rican patients were homozygous for the 16-bp duplication, whereas none of the non-Puerto Rican patients carried this mutation. Like the patients without the duplication, the patients with the 16-bp duplication had a broad variation in pigmentation. Nine of 16 adults with the duplication, but none of the 10 without it, had a diffusing capacity for carbon monoxide that was less than 80 percent of the predicted value. High-resolution computed tomography in 12 patients with the 16-bp duplication revealed minimal fibrosis in 8, moderate fibrosis in 1, severe fibrosis in 1, and no fibrosis in 2. Computed tomography in eight patients without the duplication revealed minimal fibrosis in three and no fibrosis in the rest. Inflammatory bowel disease developed in eight patients (four in each group) between 3 and 25 years of age.

CONCLUSIONS

The 16-bp duplication in exon 15 of HPS, which we found only in Puerto Rican patients, is associated with a broad range of pigmentation and an increased risk of restrictive lung disease in adults.

Mutation analysis of patients with Hermansky-Pudlak syndrome: a frameshift hot spot in the HPS gene and apparent locus heterogeneity

Hermansky-Pudlak syndrome (HPS) is a rare, autosomal recessive disorder in which oculocutaneous albinism, bleeding, and lysosomal ceroid storage result from defects of multiple cytoplasmic organelles-melanosomes, platelet-dense granules, and lysosomes. As reported elsewhere, we mapped the human HPS gene to chromosome segment 10q23, positionally cloned the gene, and identified three pathologic mutations of the gene, in patients from Puerto Rico, Japan, and Europe. Here, we describe mutation analysis of 44 unrelated Puerto Rican and 24 unrelated non-Puerto Rican HPS patients. A 16-bp frameshift duplication, the result of an apparent founder effect, is nearly ubiquitous among Puerto Rican patients. A frameshift at codon 322 may be the most frequent HPS mutation in Europeans. We also describe six novel HPS mutations: a 5' splice-junction mutation of IVS5, three frameshifts, a nonsense mutation, and a one-codon in-frame deletion. These mutations define an apparent frameshift hot spot at codons 321-322. Overall, however, we detected mutations in the HPS gene in only about half of non-Puerto Rican patients, and we present evidence that suggests locus heterogeneity for HPS.

Organization and nucleotide sequence of the human Hermansky-Pudlak syndrome (HPS) gene

Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder characterized by oculocutaneous albinism, bleeding tendency, and lysosomal ceroid storage disease, associated with defects of multiple cytoplasmic organelles-melanosomes, platelet-dense granules, and lysosomes. HPS is frequently fatal and is the most common single-gene disorder in Puerto Rico. We previously characterized the human HPS cDNA and identified pathologic mutations in the gene in patients with HPS. The HPS protein is a novel apparent transmembrane polypeptide that seems to be crucial for normal organellar development. Here we describe the structural organization, nucleotide sequence, and polymorphisms of the human HPS gene. The gene consists of 20 exons spanning about 30.5 kb in chromosome segment 10q23.1-q23.3. One of the intervening sequences is a member of the novel, very rare class of so-called "AT-AC" introns, defined by highly atypical 5' and 3' splice site and branch site consensus sequences that provide novel targets for possible pathologic gene mutations. This information provides the basis for molecular analyses of patients with HPS and will greatly facilitate diagnosis and carrier detection of this severe disorder.

Mouse pale ear (ep) is homologous to human Hermansky-Pudlak syndrome and contains a rare 'AT-AC' intron

Hermansky-Pudlak syndrome (HPS) is a rare, often fatal, autosomal recessive disorder in which albinism, bleeding and lysosomal storage are associated with defects of diverse cytoplasmic organelles, including melanosomes, platelet dense granules and lysosomes. Similar multi-organellar defects occur in the Chediak-Higashi syndrome (CHS), as well as in a large number of different mouse mutants. The HPS gene is located in 10q23, and two genetically distinct mouse loci, pale ear (ep) and ruby-eye (ru), both with mutant phenotypes similar to human HPS, map close together in the homologous region of murine chromosome 19, suggesting that one of these loci might be homologous to human HPS. We recently identified the human HPS gene, which encodes a novel ubiquitously-expressed transmembrane protein of unknown function. Here, we describe characterization of the mouse Hps cDNA and genomic locus, and identification of pathologic Hps gene mutations in ep but not in ru mice, establishing mouse pale ear as an animal model for human HPS. The phenotype of homozygous ep mutant mice encompasses those of both HPS and CHS, suggesting that these disorders may be closely related. In addition, the mouse and human HPS genes both contain a rare 'AT-AC' intron, and comparison of the sequences of this intron in the mouse and human genes identified conserved sequences that suggest a possible role for pre-mRNA secondary structure in excision of this rare class of introns.

Positional cloning of a gene for Hermansky-Pudlak syndrome, a disorder of cytoplasmic organelles

Hermansky-Pudlak syndrome (HPS) is an often-fatal autosomal recessive disease in which albinism, bleeding, and lysosomal storage result from defects of diverse cytoplasmic organelles: melanosomes, platelet dense bodies, and lysosomes. HPS is the most common single-gene disorder in Puerto Rico, with an incidence of 1 in 1,800. We have identified the HPS gene by positional cloning, and found homozygous frameshifts in this gene in Puerto Rican, Swiss, Irish and Japanese HPS patients. The HPS polypeptide is a novel transmembrane protein that is likely to be a component of multiple cytoplasmic organelles and that is apparently crucial for their normal development and function. The different clinical phenotypes associated with the different HPS frameshifts we observed suggests that differentially truncated HPS polypeptides may have somewhat different consequences for subcellular function.

Thioredoxin reductase induction coincides with melanin biosynthesis in brown and black guinea pigs and in murine melanoma cells

X-rays were used to induce melanin biosynthesis in brown and black guinea pigs in vivo. During the course of pigmentation, the expression of thioredoxin reductase was increased, whereas for the other antioxidant enzymes, superoxide dismutase (cytosol Cu/Zn-enzyme), catalase, and glutathione reductase, levels and activities decreased. Isobutylmethylxanthine induced eumelanin biosynthesis in murine melanoma cells (Cloudman S-91). In these cells, thioredoxin reductase levels coincided with melanogenesis. Our results suggest that both tyrosinase and thioredoxin reductase respond to oxidative stress in the epidermis as well as in melanoma cells and react with superoxide anion radicals to stimulate melanogenesis and to prevent peroxidative damage, respectively.