Spectrum of LYST mutations in Chediak-Higashi syndrome: a report of novel variants and a comprehensive review of the literature.

INTRODUCTION: Chediak-Higashi syndrome (CHS) is a rare autosomal recessive disorder characterised by partial oculocutaneous albinism, a bleeding diathesis, immunological dysfunction and neurological impairment. Bi-allelic loss-of-function variants in LYST cause CHS. LYST encodes the lysosomal trafficking regulator, a highly conserved 429 kDa cytoplasmic protein with an unknown function. METHODS: To further our understanding of the pathogenesis of CHS, we conducted clinical evaluations on individuals with CHS enrolled in our natural history study. Using genomic DNA Sanger sequencing, we identified novel pathogenic LYST variants. Additionally, we performed an extensive literature review to curate reported LYST variants and classified these novel and reported variants according to the American College of Medical Genetics/Association for Molecular Pathology variant interpretation guidelines. RESULTS: Our investigation unveiled 11 novel pathogenic LYST variants in eight patients with a clinical diagnosis of CHS, substantiated by the presence of pathognomonic giant intracellular granules. From these novel variants, together with a comprehensive review of the literature, we compiled a total of 147 variants in LYST, including 61 frameshift variants (41%), 44 nonsense variants (30%), 23 missense variants (16%), 13 splice site variants or small genomic deletions for which the coding effect is unknown (9%), 5 in-frame variants (3%) and 1 start-loss variant (1%). Notably, a genotype-phenotype correlation emerged, whereby individuals harbouring at least one missense or in-frame variant generally resulted in milder disease, while those with two nonsense or frameshift variants generally had more severe disease. CONCLUSION: The identification of novel pathogenic LYST variants and improvements in variant classification will provide earlier diagnoses and improved care to individuals with CHS.

Rare Pseudo-Chediak-Higashi Inclusions in Therapy-Related Acute Myeloid Leukemia with Myelodysplasia-Related Changes.

BACKGROUND: Defined as rare large azurophilic cytoplasmic inclusions, Pseudo-Chediak-Higashi granules mimic those in granulocytes cytoplasm of Chediak-Higashi syndrome. Rare cases of hematopoietic and lymphoid tissues tumors showed Pseudo-Chediak-Higashi inclusions in cytoplasm, some of which presented with unusual morphological characteristics. METHODS: Herein, we report the first case, in which rare pseudo-Chediak-Higashi inclusions were observed in therapy-related acute myeloid leukemia with myelodysplasia-related changes (t-AML-MRC). RESULTS: The rare pseudo-Chediak-Higashi inclusions may be positive for Sudan black, and some scholars think that these rare inclusions are a kind of dysgranulopoiesis. CONCLUSIONS: The case highlights the significance of an integrated diagnostic work-up, with an interesting effect for morphology.

Chediak-Higashi syndrome.

PURPOSE OF REVIEW: Chediak-Higashi syndrome is a rare autosomal recessive disorder characterized by congenital immunodeficiency, bleeding diathesis, pyogenic infection, partial oculocutaneous albinism, and progressive neurodegeneration. Treatment is hematopoietic stem cell transplantation or bone marrow transplantation; however, this does not treat the neurologic aspect of the disease. Mutations in the lysosomal trafficking regulator (LYST) gene were identified to be causative of Chediak-Higashi, but despite many analyses, there is little functional information about the LYST protein. This review serves to provide an update on the clinical manifestations and cellular defects of Chediak-Higashi syndrome. RECENT FINDINGS: More recent papers expand the neurological spectrum of disease in CHS, to include hereditary spastic paraplegia and parkinsonism. Granule size and distribution in NK cells have been investigated in relation to the location of mutations in LYST. Patients with mutations in the ARM/HEAT domain had markedly enlarged granules, but fewer in number. By contrast, patients with mutations in the BEACH domain had more numerous granules that were normal in size to slightly enlarged, but demonstrated markedly impaired polarization. The role of LYST in autophagosome formation has been highlighted in recent studies; LYST was defined to have a prominent role in autophagosome lysosome reformation for the maintenance of lysosomal homeostasis in neurons, while in retinal pigment epithelium cells, LYST deficiency was shown to lead to phagosome accumulation. SUMMARY: Despite CHS being a rare disease, investigation into LYST provides an understanding of basic vesicular fusion and fission. Understanding of these mechanisms may provide further insight into the function of LYST.

El niño plateado: Síndrome de Chediak-Higashi / The Silver Child: Chediak-Higashi Syndrome

El Síndrome de Chediak-Higashi (SCH) es una patología de herencia autosómica recesiva debido principalmente a mutaciones del gen regulador del tráfico lisosómico (LYST), causando grados dermatológicamente diferentes de albinismo óculocutáneo, infecciones recurrentes, disfunción fagocítica primaria, en el desarrollo y proliferación de todas las líneas celulares. Se presenta caso de preescolar masculino de 2 años de edad, ingresado por aumento de volumen bilateral en región cervical y fiebre, en malas condiciones generales, con áreas de hiperpigmentación en piel, cabello y cejas de coloración grisácea, adenopatías generalizadas y visceromegalias; leucocitosis con linfocitosis y neutropenia, anemia, trombocitopenia, hipoalbuminemia, hipertrigliceridemia e hiperferritinemia; en vista de la infrecuente coexistencia de dichas características con albinismo óculocutáneo; es evaluado por hematología y dermatología evidenciándose inclusiones citoplasmáticas y melanosomas gigantes, respectivamente, compatibles con SCH, confirmándose diagnóstico. El conocimiento del SCH es importante para la oportuna sospecha clínica-diagnóstica e inicio de protocolos terapéuticos en consenso, que garanticen un manejo eficaz para su sobrevida(AU)

Chediak-Higashi syndrome (SCH) is an auto somal recessive in herited pathology mainly due to mutations ofthe LYST gene, causing dermatologically different degrees of oculocutaneous albinism, recurrent infections, primary phagocytic dysfunction, in the development and proliferation of all cell lines. We present a case of a 2-year-old male preschool, admitted due to bilateral volume increase in thecervical region and fever, in poor general conditions, with areas of hyperpigmentation in skin, hair and eyebrows of grayish coloration, generalized lymphadenopathy and visceromegaly; leukocytosis with lymphocytosis and neutropenia, anemia, thrombocytopenia, hypoalbuminemia, hypertriglyceridemia,and hyperferritinemia; in view of the infrequent coexistence of these characteristics with oculocutaneous albinism; it isevaluated by hematology and dermatology, showing cytoplasmicinclusions and giant melanosomes, respectively, compatiblewith SCH, confirming the diagnosis. Knowledge of SCH is important for timely clinical-diagnostic suspicion and initiation of consensus therapeutic protocols that guarantee effective management for survival(AU)

Successful use of emapalumab in refractory hemophagocytic lymphohistiocytosis in a child with Chédiak-Higashi syndrome: a case report.

BACKGROUND: Hemophagocytic lymphohistiocytosis is a life-threatening disease heralded by fever, cytopenia, hepatosplenomegaly, and multisystem organ failure. Its association with genetic mutations, infections, autoimmune disorders, and malignancies is widely reported. CASE PRESENTATION: A 3-year-old male Arab Saudi patient with insignificant past medical history and parental consanguinity presented with abdominal distension of moderate severity and persistent fever despite receiving antibiotics. This was accompanied by hepatosplenomegaly and silvery hair. The clinical and biochemical profiles were suggestive of Chédiak-Higashi syndrome with hemophagocytic lymphohistiocytosis. The patient received the hemophagocytic lymphohistiocytosis-2004 chemotherapy protocol and had multiple hospital admissions mainly due to infections and febrile neutropenia. After achieving the initial remission, the patient's disease reactivated and did not respond to reinduction with the hemophagocytic lymphohistiocytosis-2004 protocol. Due to the disease reactivation and intolerance of conventional therapy, the patient commenced emapalumab. The patient was successfully salvaged and underwent an uneventful hematopoietic stem cell transplantation. CONCLUSIONS: Novel agents such as emapalumab can be helpful for the management of refractory, recurrent, or progressive disease, while avoiding the toxicities of conventional therapy. Due to a paucity of available data on emapalumab, additional data are needed to establish its role in hemophagocytic lymphohistiocytosis treatment.

LYST deficiency impairs autophagic lysosome reformation in neurons and alters lysosome number and size.

Chediak-Higashi syndrome (CHS) is a rare, autosomal recessive disorder caused by biallelic mutations in the lysosomal trafficking regulator (LYST) gene. Even though enlarged lysosomes and/or lysosome-related organelles (LROs) are the typical cellular hallmarks of CHS, they have not been investigated in human neuronal models. Moreover, how and why the loss of LYST function causes a lysosome phenotype in cells has not been elucidated. We report that the LYST-deficient human neuronal model exhibits lysosome depletion accompanied by hyperelongated tubules extruding from enlarged autolysosomes. These results have also been recapitulated in neurons differentiated from CHS patients' induced pluripotent stem cells (iPSCs), validating our model system. We propose that LYST ensures the correct fission/scission of the autolysosome tubules during autophagic lysosome reformation (ALR), a crucial process to restore the number of free lysosomes after autophagy. We further demonstrate that LYST is recruited to the lysosome membrane, likely to facilitate the fission of autolysosome tubules. Together, our results highlight the key role of LYST in maintaining lysosomal homeostasis following autophagy and suggest that ALR dysregulation is likely associated with the neurodegenerative CHS phenotype.

Oral manifestations of Chediak-Higashi syndrome: A systematic review.

Chediak-Higashi syndrome (CHS) is an autosomal recessive disorder characterized by leukocytes with giant secretory granules and a myriad of clinical features. However, it is unknown whether oral lesions are part of the syndrome or are refractory to systemic treatment. Herein, we integrated the available data published in the literature on the oral manifestations of individuals with CHS. Searches on PubMed, Web of Science, Embase, Scopus, and LILACS were conducted to identify studies published up to March/2022. The Joanna Briggs Institute tool was used for the critical appraisal of studies. Fourteen articles (21 cases) were detected. The mean age of individuals was 15.9±8.8 years. There was a slight predominance of males (52.4%). The major manifestation was periodontal disease (81%), although ulceration of the oral mucosa (14.3%), gingival/labial abscess (4.8%), and periodontal abscess (4.8%) were also reported. Oral rehabilitation including dental implants (9.5%) was performed after tooth losses due to the poor prognosis of periodontal therapy. CHS is usually diagnosed in an early stage due to its systemic manifestations such as classic oculocutaneous albinism, recurrent infections, and a propensity for bleeding. Oral health providers should be aware of the manifestations of individuals with CHS. Special care, including oral prophylaxis, is indispensable.

Chediak Higashi Syndrome with Hemophagocytic Lymphohistiocytosis.

INTRODUCTION: Chediak-Higashi syndrome (CHS) is caused by dysfunction of lysosomal trafficking and presents with hypopigmentation, bleeding tendencies, neurological symptoms, and NK cell dysfunction. Hemophagocytic lymphohistiocytosis (HLH) can complicate CHS due to the abnormal function of NK cells. CASE PRESENTATION: This 1.5-year-old light-skinned gray-haired girl microscopically had abnormal hair pigment clumps and lilac inclusions in the myeloid series, characteristic of CHS. She presented with HLH, requiring treatment with etoposide and dexamethasone followed by cyclosporine and dexamethasone. CONCLUSION: CHS is one of the underlying primary causes of HLH.

[Identification of novel variants in a Chinese patient with Chediak-Higashi syndrome].

OBJECTIVE: To explore the genetic basis for a child featuring Chediak-Higashi syndrome (CHS). METHODS: Clinical manifestations and results of auxiliary examination of the proband were analyzed. The proband was subjected to whole exome sequencing, and the results were verified by Sanger sequencing. Correlation between the genotype and clinical phenotype was analyzed. RESULTS: The proband showed partial skin albinism, recurrent respiratory infection and other immune deficiencies. Genetic testing showed that he has harbored c.2437C>T (p.Arg813*) and c.6077dupA (p.Tyr2026fs) (NM_000081) compound heterozygous variants of the LYST gene, for which his parents were both carriers. Neither variant was reported previously. HEAT repeats domain was frequently associated with more severe phenotype of CHS (81.6%), whilst no variant has been found in the PH_BEACH domain. CONCLUSION: This study has enriched the spectrum of LYST gene variants associated with CHS and enabled clinical diagnosis, prenatal diagnosis and prognostic evaluation for the child.

iPS cells from Chediak-Higashi syndrome patients recapitulate the giant granules in myeloid cells.

BACKGROUND: Chediak-Higashi syndrome (CHS) is a congenital disease characterized by immunodeficiency, hemophagocytic lymphohistiocytosis, oculocutaneous albinism, and neurological symptoms. The presence of giant granules in peripheral blood leukocytes is an important hallmark of CHS. Here we prepared induced pluripotent stem cells (iPSCs) from CHS patients (CHS-iPSCs) and differentiated them into hematopoietic cells to model the disease phenotypes. METHODS: Fibroblasts were obtained from two CHS patients and then reprogrammed into iPSCs. The iPSCs were differentiated into myeloid cells; the size of the cytosolic granules was quantified by May-Grunwald Giemsa staining and myeloperoxidase staining. RESULTS: Two clones of iPSCs were established from each patient. The differentiation efficiency to CD33+ CD45+ myeloid cells was not significantly different in CHS-iPSCs compared with control iPSCs, but significantly larger granules were observed. CONCLUSIONS: We succeeded in reproducing a characteristic cellular phenotype, giant granules in myeloid cells, using CHS-iPSCs, demonstrating that iPSCs can be used to model the pathogenesis of CHS patients.

Effect of vitamin C supplementation on some leukocyte parameters in American mink (Neovison vison) with abnormal granulogenesis.

Sapphire mink, a mutant colour variant of American mink, is an animal model of the Chediak-Higashi syndrome (CHS). As in CHS, there are enlarged cytoplasmic granules in various cell types including leukocytes in Sapphire mink due to abnormal granulogenesis. Such cellular abnormality leads to a weakening of the immune defence as a consequence to the development of infections. A study with Sapphire mink and Standard mink was conducted to evaluate the immunostimulant effect of vitamin C (VC) supplementation (100 mg/day) on some leukocyte parameters. In the end of the 20-day treatment period, blood samples were collected to determine hematological (total and differential leukocyte counts, red blood cells (RBC) counts, and haemoglobin level) and cytochemical (activity and staining area of myeloperoxidase, eosinophilc peroxidase, alkaline phosphatase, and alpha naphthyl acetate esterase) parameters. The study showed that total leukocyte counts, segmented neutrophil counts, and monocyte counts were significantly (p < 0.05) higher in Sapphire mink from the VC-supplemented group than in those receiving the control diet. These results indicate that VC supplementation may have a positive effect on immunity in Sapphire mink. Another interesting finding is an increase in the number of neutrophils with enlarged granules and lysosomal enzyme-positive area in VC-supplemented mink as compared with those fed the control diet. These observations suggest that VC supplementation can affect the lysosomal apparatus of leukocytes.

The yeast LYST homolog Bph1 is a Rab5 effector and prevents Atg8 lipidation at endosomes.

Lysosomes mediate degradation of macromolecules to their precursors for cellular recycling. Additionally, lysosome-related organelles mediate cell type-specific functions. Chédiak-Higashi syndrome is an autosomal, recessive disease, in which loss of the protein LYST causes defects in lysosomes and lysosome-related organelles. The molecular function of LYST, however, is largely unknown. Here, we dissected the function of the yeast LYST homolog, Bph1. We show that Bph1 is an endosomal protein and an effector of the minor Rab5 isoform Ypt52. Strikingly, bph1Δ mutant cells have lipidated Atg8 on their endosomes, which is sorted via late endosomes into the vacuole lumen under non-autophagy-inducing conditions. In agreement with this, proteomic analysis of bph1Δ vacuoles reveals an accumulation of Atg8, reduced flux via selective autophagy, and defective endocytosis. Additionally, bph1Δ cells have reduced autophagic flux under starvation conditions. Our observations suggest that Bph1 is a novel Rab5 effector that maintains endosomal functioning. When Bph1 is lost, Atg8 is lipidated at endosomes even during normal growth and ends up in the vacuole lumen. Thus, our results contribute to the understanding of the role of LYST-related proteins and associated diseases.