Pulmonary function and structure abnormalities in children and young adults with osteogenesis imperfecta point to intrinsic and extrinsic lung abnormalities.

PURPOSE: Pulmonary disease is the major cause of morbidity and mortality in osteogenesis imperfecta (OI). We investigated the contribution of intrinsic lung factors to impaired pulmonary function in children and young adults with OI types III, IV, VI. METHODS: Patients with type III (n=8), IV (n=21), VI (n=5), VII (n=2) or XIV (n=1) OI (mean age 23.6 years) prospectively underwent pulmonary function tests (PFTs) and thoracic CT and radiographs. RESULTS: PFT results were similar using arm span or ulnar length as height surrogates. PFTs were significantly lower in type III than type IV or VI OI. All patients with type III and half of type IV OI had lung restriction; 90% of patients with OI had reduced gas exchange. Patients with COL1A1 variants had significantly lower forced expiratory flow (FEF)25%-75% compared with those with COL1A2 variants. PFTs correlated negatively with Cobb angle or age. CT scans revealed small airways bronchial thickening (100%, 86%, 100%), atelectasis (88%, 43%, 40%), reticulations (50%, 29%, 20%), ground glass opacities (75%, 5%, 0%), pleural thickening (63%, 48%, 20%) or emphysema (13%, 19%, 20%) in type III, IV or VI OI, respectively. CONCLUSION: Both lung intrinsic and extrinsic skeletal abnormalities contribute to OI pulmonary dysfunction. Most young adult patients have restrictive disease and abnormal gas exchange; impairment is greater in type III than type IV OI. Decreased FEF25%-75% and thickening of small bronchi walls indicate a critical role for small airways. Lung parenchymal abnormalities (atelectasis, reticulations) and pleural thickening were also detected. Clinical interventions to mitigate these impairments are warranted. TRIAL REGISTRATION NUMBER: NCT03575221.

Hermansky-Pudlak syndrome: Gene therapy for pulmonary fibrosis.

Pulmonary fibrosis is a progressive and often fatal lung disease that manifests in most patients with Hermansky-Pudlak syndrome (HPS) type 1. Although the pathobiology of HPS pulmonary fibrosis is unknown, several studies highlight the pathogenic roles of different cell types, including type 2 alveolar epithelial cells, alveolar macrophages, fibroblasts, myofibroblasts, and immune cells. Despite the identification of the HPS1 gene and progress in understanding the pathobiology of HPS pulmonary fibrosis, specific treatment for HPS pulmonary fibrosis is not available, emphasizing the need to identify cellular and molecular targets and to develop therapeutic strategies for this devastating disease. This commentary summarizes recent advances and aims to provide insights into gene therapy for HPS pulmonary fibrosis.

Progressive pulmonary fibrosis in a murine model of Hermansky-Pudlak syndrome.

BACKGROUND: HPS-1 is a genetic type of Hermansky-Pudlak syndrome (HPS) with highly penetrant pulmonary fibrosis (HPSPF), a restrictive lung disease that is similar to idiopathic pulmonary fibrosis (IPF). Hps1ep/ep (pale ear) is a naturally occurring HPS-1 mouse model that exhibits high sensitivity to bleomycin-induced pulmonary fibrosis (PF). Traditional methods of administering bleomycin as an intratracheal (IT) route to induce PF in this model often lead to severe acute lung injury and high mortality rates, complicating studies focusing on pathobiological mechanisms or exploration of therapeutic options for HPSPF. METHODS: To develop a murine model of HPSPF that closely mimics the progression of human pulmonary fibrosis, we investigated the pulmonary effects of systemic delivery of bleomycin in Hps1ep/ep mice using a subcutaneous minipump and compared results to oropharyngeal delivery of bleomycin. RESULTS: Our study revealed that systemic delivery of bleomycin induced limited, acute inflammation that resolved. The distinct inflammatory phase preceded a slow, gradually progressive fibrogenesis that was shown to be both time-dependent and dose-dependent. The fibrosis phase exhibited characteristics that better resembles human disease with focal regions of fibrosis that were predominantly found in peribronchovascular areas and in subpleural regions; central lung areas contained relatively less fibrosis. CONCLUSION: This model provides a preclinical tool that will allow researchers to study the mechanism of pulmonary fibrosis in HPS and provide a platform for the development of therapeutics to treat HPSPF. This method can be applied on studies of IPF or other monogenic disorders that lead to pulmonary fibrosis.

Dysregulated myosin in Hermansky-Pudlak syndrome lung fibroblasts is associated with increased cell motility.

Hermansky-Pudlak syndrome (HPS) is an autosomal recessive disorder characterized by improper biogenesis of lysosome-related organelles (LROs). Lung fibrosis is the leading cause of death among adults with HPS-1 and HPS-4 genetic types, which are associated with defects in the biogenesis of lysosome-related organelles complex-3 (BLOC-3), a guanine exchange factor (GEF) for a small GTPase, Rab32. LROs are not ubiquitously present in all cell types, and specific cells utilize LROs to accomplish dedicated functions. Fibroblasts are not known to contain LROs, and the function of BLOC-3 in fibroblasts is unclear. Here, we report that lung fibroblasts isolated from patients with HPS-1 have increased migration capacity. Silencing HPS-1 in normal lung fibroblasts similarly leads to increased migration. We also show that the increased migration is driven by elevated levels of Myosin IIB. Silencing HPS1 or RAB32 in normal lung fibroblasts leads to increased MYOSIN IIB levels. MYOSIN IIB is downstream of p38-MAPK, which is a known target of angiotensin receptor signaling. Treatment with losartan, an angiotensin receptor inhibitor, decreases MYOSIN IIB levels and impedes HPS lung fibroblast migration in vitro. Furthermore, pharmacologic inhibition of angiotensin receptor with losartan seemed to decrease migration of HPS lung fibroblasts in vivo in a zebrafish xenotransplantation model. Taken together, we demonstrate that BLOC-3 plays an important role in MYOSIN IIB regulation within lung fibroblasts and contributes to fibroblast migration.

Hermansky-Pudlak syndrome-2 alters mitochondrial homeostasis in the alveolar epithelium of the lung.

BACKGROUND: Mitochondrial dysfunction has emerged as an important player in the pathogenesis of idiopathic pulmonary fibrosis (IPF), a common cause of idiopathic interstitial lung disease in adults. Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive disorder that causes a similar type of pulmonary fibrosis in younger adults, although the role of mitochondrial dysfunction in this condition is not understood. METHODS: We performed a detailed characterization of mitochondrial structure and function in lung tissues and alveolar epithelial cells deficient in the adaptor protein complex 3 beta 1 (Ap3b1) subunit, the gene responsible for causing subtype 2 of HPS (HPS-2). RESULTS: We observed widespread changes in mitochondrial homeostasis in HPS-2 cells, including the acquisition of abnormally shaped mitochondria, with reduced number of cristae, and markedly reduced activity of the electron transport chain and the tricarboxylic acid cycle. We also found that mitochondrial redox imbalance and activity of the mitochondrial unfolded protein response were dysregulated in HPS-2 cells and this associated with various other changes that appeared to be compensatory to mitochondrial dysfunction. This included an increase in glycolytic activity, an upregulation in the expression of mitochondrial biogenesis factors and enhanced activation of the energy-conserving enzyme AMP-activated protein kinase. CONCLUSION: In summary, our findings indicate that mitochondrial function is dramatically altered in HPS-2 lung tissues, suggesting dysfunction of this organelle might be a driver of HPS lung disease.

Survivorship Issues in Adult Patients With Histiocytic Neoplasms.

Adult-onset histiocytoses (AOH), primarily Rosai-Dorfman disease (RDD), Erdheim-Chester Disease (ECD), and adult Langerhans cell histiocytosis (ALCH), are a group of related histiocytic neoplastic disorders featuring multisystemic manifestations. The disorders are largely incurable, and are essentially chronic neoplastic diseases with a variable prognosis. Prompt diagnosis and treatment is important to prevent debilitating and even life-threatening complications. Survivorship issues abound in AOH, due to their multisystemic manifestations and the sometimes recalcitrant chronic inflammation, which can lead to other debilitating complications such as fatigue, weakness, and pain. Because these disorders are rare, few healthcare professionals are proficient in their management; therefore the aim of these guidelines is to offer guidance on how to manage patients, and how to create survivorship care plans through the efforts of an interdisciplinary team.

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.

Bleomycin Induces Drug Efflux in Lungs. A Pitfall for Pharmacological Studies of Pulmonary Fibrosis.

ATP-binding cassette (ABC) transporters are evolutionarily conserved membrane proteins that pump a variety of endogenous substrates across cell membranes. Certain subfamilies are known to interact with pharmaceutical compounds, potentially influencing drug delivery and treatment efficacy. However, the role of drug resistance-associated ABC transporters has not been examined in idiopathic pulmonary fibrosis (IPF) or its animal model: the bleomycin (BLM)-induced murine model. Here, we investigate the expression of two ABC transporters, P-gp (permeability glycoprotein) and BCRP (breast cancer resistance protein), in human IPF lung tissue and two different BLM-induced mouse models of pulmonary fibrosis. We obtained human IPF specimens from patients during lung transplantation and administered BLM to male C57BL/6J mice either by oropharyngeal aspiration (1 U/kg) or subcutaneous osmotic infusion (100 U/kg over 7 d). We report that P-gp and BCRP expression in lungs of patients with IPF was comparable to controls. However, murine lungs expressed increased levels of P-gp and BCRP after oropharyngeal and subcutaneous BLM administration. We localized this upregulation to multiple pulmonary cell types, including alveolar fibroblasts, endothelial cells, and type 2 epithelial cells. Functionally, this effect reduced murine lung exposure to nintedanib, a U.S. Food and Drug Administration-approved IPF therapy known to be a P-gp substrate. The study reveals a discrepancy between IPF pathophysiology and the common animal model of lung fibrosis. BLM-induced drug efflux in the murine lungs may present an uncontrolled confounding variable in the preclinical study of IPF drug candidates, and these findings will facilitate disease model validation and enhance new drug discoveries that will ultimately improve patient outcomes.

Diagnosis of Chediak Higashi disease in a 67-year old woman.

Chediak-Higashi disease is a rare disease caused by bi-allelic mutations in the lysosomal trafficking regulator gene, LYST. Individuals typically present in early childhood with partial oculocutaneous albinism, a bleeding diathesis, recurrent infections secondary to immune dysfunction, and risk of developing hemophagocytic lymphohistiocytosis (HLH). Without intervention, mortality is high in the first decade of life. However, some individuals with milder phenotypes have attenuated hematologic and immunologic presentations, and lower risk of HLH. Both classic and milder phenotypes develop progressive neurodegeneration in early adulthood. Here we present a remarkable patient diagnosed with Chediak-Higashi disease at age 67, many decades after the diagnosis is usually established. Diagnosis was suspected by observing the pathognomonic granules within leukocytes, and confirmed by identification of bi-allelic mutations in LYST, reduced LYST mRNA expression, enlarged lysosomes within fibroblasts, and decreased NK cell lytic activity. This case further expands the phenotype of Chediak-Higashi disease and highlights the need for increased awareness. Individuals with milder phenotypes may escape early diagnosis, but identification is important for close monitoring of potential complications, and to further our understanding of the function of LYST.

Galectin-3 Interacts with the CHI3L1 Axis and Contributes to Hermansky-Pudlak Syndrome Lung Disease.

Hermansky-Pudlak syndrome (HPS) comprises a group of inherited disorders caused by mutations that alter the function of lysosome-related organelles. Pulmonary fibrosis is the major cause of morbidity and mortality in HPS-1 and HPS-4 patients. However, the mechanisms that underlie the exaggerated injury and fibroproliferative repair responses in HPS have not been adequately defined. In particular, although Galectin-3 (Gal-3) is dysregulated in HPS, its roles in the pathogenesis of HPS have not been adequately defined. In addition, although chitinase 3-like 1 (CHI3L1) and its receptors play major roles in the injury and repair responses in HPS, the ability of Gal-3 to interact with or alter the function of these moieties has not been evaluated. In this article, we demonstrate that Gal-3 accumulates in exaggerated quantities in bronchoalveolar lavage fluids, and traffics abnormally and accumulates intracellularly in lung fibroblasts and macrophages from bleomycin-treated pale ear, HPS-1-deficient mice. We also demonstrate that Gal-3 drives epithelial apoptosis when in the extracellular space, and stimulates cell proliferation and myofibroblast differentiation when accumulated in fibroblasts and M2-like differentiation when accumulated in macrophages. Biophysical and signaling evaluations also demonstrated that Gal-3 physically interacts with IL-13Rα2 and CHI3L1, and competes with TMEM219 for IL-13Rα2 binding. By doing so, Gal-3 diminishes the antiapoptotic effects of and the antiapoptotic signaling induced by CHI3L1 in epithelial cells while augmenting macrophage Wnt/ß-catenin signaling. Thus, Gal-3 contributes to the exaggerated injury and fibroproliferative repair responses in HPS by altering the antiapoptotic and fibroproliferative effects of CHI3L1 and its receptor complex in a tissue compartment-specific manner.

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.

Expanding the phenotype of COPA syndrome: a kindred with typical and atypical features.

BACKGROUND: Copa syndrome is a rare autosomal dominant disorder with abnormal intracellular vesicle trafficking. The objective of this work is to expand the knowledge about this disorder by delineating phenotypic features of an unreported COPA family. METHODS AND RESULTS: A heterozygous missense variant (c.698 G>A, p.Arg233His) in COPA was identified in four members of a three-generation kindred with lung, autoimmune and malignant disease of unknown aetiology. Ages of onset were 56, 26, 16 and 1 year, with earlier age of onset in successive generations. Presenting symptoms were cough and dyspnoea. Findings included small lung cysts, follicular bronchiolitis, interstitial lung disease, neuroendocrine cell hyperplasia, rheumatoid arthritis, avascular necrosis and select abnormal autoimmune serologies. Neither alveolar haemorrhage nor glomerular disease were present. Features not previously associated with Copa syndrome included neuromyelitis optica, pulmonary carcinoid tumour, clear cell renal carcinoma, renal cysts, hepatic cysts, nephrolithiasis, pyelonephritis and meningitis. Longitudinal evaluations demonstrated slow progression of lung disease and extrapulmonary cysts. CONCLUSIONS: Worsening severity with successive generations may be observed in Copa syndrome. Extrapulmonary cysts, malignancies, autoimmune neurological disorders and infections are clinical features that may be associated with Copa syndrome. Further studies are indicated to fully define the phenotypic spectrum of this disorder.

Danazol Treatment for Telomere Diseases.

BACKGROUND: Genetic defects in telomere maintenance and repair cause bone marrow failure, liver cirrhosis, and pulmonary fibrosis, and they increase susceptibility to cancer. Historically, androgens have been useful as treatment for marrow failure syndromes. In tissue culture and animal models, sex hormones regulate expression of the telomerase gene. METHODS: In a phase 1-2 prospective study involving patients with telomere diseases, we administered the synthetic sex hormone danazol orally at a dose of 800 mg per day for a total of 24 months. The goal of treatment was the attenuation of accelerated telomere attrition, and the primary efficacy end point was a 20% reduction in the annual rate of telomere attrition measured at 24 months. The occurrence of toxic effects of treatment was the primary safety end point. Hematologic response to treatment at various time points was the secondary efficacy end point. RESULTS: After 27 patients were enrolled, the study was halted early, because telomere attrition was reduced in all 12 patients who could be evaluated for the primary end point; in the intention-to-treat analysis, 12 of 27 patients (44%; 95% confidence interval [CI], 26 to 64) met the primary efficacy end point. Unexpectedly, almost all the patients (11 of 12, 92%) had a gain in telomere length at 24 months as compared with baseline (mean increase, 386 bp [95% CI, 178 to 593]); in exploratory analyses, similar increases were observed at 6 months (16 of 21 patients; mean increase, 175 bp [95% CI, 79 to 271]) and 12 months (16 of 18 patients; mean increase, 360 bp [95% CI, 209 to 512]). Hematologic responses occurred in 19 of 24 patients (79%) who could be evaluated at 3 months and in 10 of 12 patients (83%) who could be evaluated at 24 months. Known adverse effects of danazol--elevated liver-enzyme levels and muscle cramps--of grade 2 or less occurred in 41% and 33% of the patients, respectively. CONCLUSIONS: In our study, treatment with danazol led to telomere elongation in patients with telomere diseases. (Funded by the National Institutes of Health; ClinicalTrials.gov number, NCT01441037.).

Prolonged treatment with open-label pirfenidone in Hermansky-Pudlak syndrome pulmonary fibrosis.

PURPOSE: Limited information is available regarding chronic treatment with pirfenidone, an anti-fibrotic drug. Effects of long-term open-label pirfenidone were evaluated in a small cohort with Hermansky-Pudlak syndrome (HPS), a rare autosomal recessive disorder with highly penetrant pulmonary fibrosis. RESULTS: Three patients with HPS pulmonary fibrosis treated with open-label pirfenidone and twenty-one historical controls randomized to placebo were studied at a single center. Mean duration of treatment with pirfenidone for 3 patients with HPS pulmonary fibrosis was 13.1 years. Annual changes in FVC and DLCO with pirfenidone treatment were 0.46 and - 0.93% predicted, respectively. In comparison, historical controls randomized to receive placebo experienced mean annual changes in FVC and DLCO of -4.4 and - 2.3% predicted, respectively. High-resolution computed tomography (HRCT) scans revealed improved ground glass opacities with development of minimal interstitial reticulations in 1 patient after 12.8 years of treatment with pirfenidone. Slowly progressive increase in bilateral interstitial fibrosis developed in a different patient, who received pirfenidone for 18.1 years and died at 73 years of age due to HPS pulmonary fibrosis. Another patient treated with pirfenidone for 8.4 years had attenuated ground glass opacification on HRCT scan and improved oxygenation; this patient died due to chronic complications from colitis, and not pulmonary fibrosis. Adverse effects were generally limited to mild gastrointestinal discomfort and transient elevations of alanine aminotransferase in one patient. CONCLUSIONS: Chronic treatment with pirfenidone may provide clinical benefit with few adverse effects for some patients with HPS pulmonary fibrosis. These results suggest that compassionate use of pirfenidone could be considered on a case-by-case basis for patients with HPS pulmonary fibrosis.

Severe bleeding with subclinical oculocutaneous albinism in a patient with a novel HPS6 missense variant.

Hermanský-Pudlák syndrome (HPS), a rare autosomal recessive disorder, manifests with oculocutaneous albinism and a bleeding diathesis. However, severity of disease can be variable and is typically related to the genetic subtype of HPS; HPS type 6 (HPS-6) is an uncommon subtype generally associated with mild disease. A Caucasian adult female presented with a history of severe bleeding; ophthalmologic examination indicated occult oculocutaneous albinism. The patient was diagnosed with a platelet storage pool disorder, and platelet whole mount electron microscopy demonstrated absent delta granules. Genome-wide SNP analysis showed regions of homozygosity that included the HPS1 and HPS6 genes. Full length HPS1 transcript was amplified by PCR of genomic DNA. Targeted next-generation sequencing identified a novel homozygous missense variant in HPS6 (c.383 T > C; p.V128A); this was associated with significantly reduced HPS6 mRNA and protein expression in the patient's fibroblasts compared to control cells. These findings highlight the variable severity of disease manifestations in patients with HPS, and illustrate that HPS can be diagnosed in patients with excessive bleeding and occult oculocutaneous albinism. Genetic analysis and platelet electron microscopy are useful diagnostic tests in evaluating patients with suspected HPS. Clinical Trial registration: Registrar: ClinicalTrials.gov Website: www.clinicaltrials.gov Registration Numbers: NCT00001456 and NCT00084305.

Extensive Citrullination Promotes Immunogenicity of HSP90 through Protein Unfolding and Exposure of Cryptic Epitopes.

Post-translational protein modifications such as citrullination have been linked to the breach of immune tolerance and clinical autoimmunity. Previous studies from our laboratory support this concept, demonstrating that autoantibodies targeting citrullinated isoforms of heat shock protein 90 (HSP90) are associated with rheumatoid arthritis complicated by interstitial lung disease. To further explore the relationship between citrullination and structural determinants of HSP90 immunogenicity, we employed a combination of ELISA-based epitope profiling, computational modeling, and mass-spectrometric sequencing of peptidylarginine deiminase (PAD)-modified protein. Remarkably, ELISAs involving selected citrullinated HSP90ß/α peptides identified a key epitope corresponding to an internal Arg residue (R502 [HSP90ß]/R510 [HSP90α]) that is normally buried within the crystal structure of native/unmodified HSP90. In vitro time/dose-response experiments reveal an ordered pattern of PAD-mediated deimination events culminating in citrullination of R502/R510. Conventional as well as scaled molecular dynamics simulations further demonstrate that citrullination of selected Arg residues leads to progressive disruption of HSP90 tertiary structure, promoting exposure of R502/R510 to PAD modification and subsequent autoantibody binding. Consistent with this process, ELISAs incorporating variably deiminated HSP90 as substrate Ag indicate a direct relationship between the degree of citrullination and the level of ex vivo Ab recognition. Overall, these data support a novel structural paradigm whereby citrullination-induced shifts in protein structure generate cryptic epitopes capable of bypassing B cell tolerance in the appropriate genetic context.

Natural killer cell activity and dysfunction in Hermansky-Pudlak syndrome.

Hermansky-Pudlak syndrome (HPS) encompasses disorders with abnormal function of lysosomes and lysosome-related organelles, and some patients who develop immunodeficiency. The basic mechanisms contributing to immune dysfunction in HPS are ill-defined. We analysed natural killer (NK) cells from patients diagnosed with HPS-1, HPS-2, HPS-4, and an unreported HPS subtype. NK cells from an HPS-2 and an unreported HPS subtype share a similar cellular phenotype with defective granule release and cytotoxicity, but differ in cytokine exocytosis. Defining NK cell activity in several types of HPS provides insights into cellular defects of the disorder and understanding of mechanisms contributing to HPS pathogenesis.

Clinical and molecular phenotyping of a child with Hermansky-Pudlak syndrome-7, an uncommon genetic type of HPS.

PURPOSE: Hermansky-Pudlak syndrome (HPS) is a rare inherited disorder with ten reported genetic types; each type has defects in subunits of either Adaptor Protein-3 complex or Biogenesis of Lysosome-related Organelles Complex (BLOC)-1, -2, or -3. Very few patients with BLOC-1 deficiency (HPS-7, -8, and -9 types) have been diagnosed. We report results of comprehensive clinical testing and molecular analyses of primary fibroblasts from a new case of HPS-7. RESULTS: A 6-year old Paraguayan male presented with hypopigmentation, ocular albinism, nystagmus, reduced visual acuity, and easy bruising. He also experienced delayed motor and language development as a very young child; head and chest trauma resulted in intracranial hemorrhage with subsequent right hemiparesis and lung scarring. There was no clinical evidence of immunodeficiency or colitis. Whole mount transmission electron microscopy revealed absent platelet delta granules; platelet aggregation testing was abnormal. Exome sequencing revealed a homozygous nonsense mutation in the Dystrobrevin binding protein 1 (DTNBP1) gene [NM_032122.4: c.307C>T; p.Gln103*], previously reported in a Portuguese adult. The gene encodes the dysbindin subunit of BLOC-1. Dysbindin protein expression was negligible in our patient's dermal fibroblasts, while his DTNBP1 mRNA level was similar to that of a normal control. CONCLUSIONS: Comprehensive clinical evaluation of the first pediatric case reported with HPS-7 reveals oculocutaneous albinism and platelet storage pool deficiency; his phenotype is consistent with findings in other patients with BLOC-1 disorders. This patient's markedly reduced Dysbindin protein expression in HPS-7 resulted from a mechanism other than nonsense mediated decay.

MAP1LC3B overexpression protects against Hermansky-Pudlak syndrome type-1-induced defective autophagy in vitro.

Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive disorder, and some patients with HPS develop pulmonary fibrosis, known as HPS-associated interstitial pneumonia (HPSIP). We have previously reported that HPSIP is associated with severe surfactant accumulation, lysosomal stress, and alveolar epithelial cell type II (AECII) apoptosis. Here, we hypothesized that defective autophagy might result in excessive lysosomal stress in HPSIP. Key autophagy proteins, including LC3B lipidation and p62, were increased in HPS1/2 mice lungs. Electron microscopy demonstrated a preferable binding of LC3B to the interior of lamellar bodies in the AECII of HPS1/2 mice, whereas in wild-type mice it was present on the limiting membrane in addition to the interior of the lamellar bodies. Similar observations were noted in human HPS1 lung sections. In vitro knockdown of HPS1 revealed increased LC3B lipidation and p62 accumulation, associated with an increase in proapoptotic caspases. Overexpression of LC3B decreased the HPS1 knockdown-induced p62 accumulation, whereas rapamycin treatment did not show the same effect. We conclude that loss of HPS1 protein results in impaired autophagy that is restored by exogenous LC3B and that defective autophagy might therefore play a critical role in the development and progression of HPSIP.