A syndrome associating partial albinism and immunodeficiency

Griscelli syndrome-type 2 in twin siblings: case report and update on RAB27A human mutations and gene structure

Griscelli syndrome (GS) is a rare autosomal recessive disorder caused by mutation in the MYO5A (GS1, Elejalde), RAB27A (GS2) or MLPH (GS3) genes. Typical features of all three subtypes of this disease include pigmentary dilution of the hair and skin and silvery-gray hair. Whereas the GS3 phenotype is restricted to the pigmentation dysfunction, GS1 patients also show primary neurological impairment and GS2 patients have severe immunological deficiencies that lead to recurrent infections and hemophagocytic syndrome. We report here the diagnosis of GS2 in 3-year-old twin siblings, with silvery-gray hair, immunodeficiency, hepatosplenomegaly and secondary severe neurological symptoms that culminated in multiple organ failure and death. Light microscopy examination of the hair showed large, irregular clumps of pigments characteristic of GS. A homozygous nonsense mutation, C-T transition (c.550C>T), in the coding region of the RAB27A gene, which leads to a premature stop codon and prediction of a truncated protein (R184X), was found. In patient mononuclear cells, RAB27A mRNA levels were the same as in cells from the parents, but no protein was detected. In addition to the case report, we also present an updated summary on the exon/intron organization of the human RAB27A gene, a literature review of GS2 cases, and a complete list of the human mutations currently reported in this gene. Finally, we propose a flow chart to guide the early diagnosis of the GS subtypes and Chédiak-Higashi syndrome.

Hematopoietic stem cell transplantation in Griscelli syndrome type 2: a single-center report on 10 patients

Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative treatment for Griscelli syndrome type 2, an inherited immune disorder causing fatal hemophagocytic lymphohistiocytosis (HLH). Optimal therapeutic modalities are not yet well known. We retrospectively analyzed the outcome for 10 patients who underwent HSCT in a single center between 1996 and 2008. Seven patients (70%) were cured of the primary immune defect (mean follow-up, 5.2 years; range, 0.8-12.0 years), 4 of them without neurologic sequelae. In the 3 deceased patients, death occurred within 110 days of HSCT and was probably due to adverse reaction to HSCT in 2 patients and to HLH relapse in one patient. One patient received 2 transplants because of graft failure. Clinical events included veno-occlusive disease (n = 5), acute (n = 7) or chronic (n = 1) graft-versus-host disease II-III, and Epstein-Barr virus–induced lymphoproliferative disease (n = 2). Of the 7 patients with neurologic involvement before HSCT, 4 survived and 2 presented sequelae. Furthermore, 1 patient lacking neurologic involvement before HSCT developed long-term sequelae. These results demonstrate the efficacy of HSCT in curing the immune disorder but also show that neurologic HLH before HSCT is a major factor, given the neurologic sequelae after otherwise successful HSCT. Additional studies are required to improve treatment.

Genetic syndromic immunodeficiencies with antibody defects

This article reviews the major syndromic immunodeficiencies with significant antibody defects, many of which may require intravenous immunogammaglobulin therapy. The authors define syndromic immunodeficiency as an illness associated with a characteristic group of phenotypic abnormalities or laboratory features that comprise a recognizable syndrome. Many are familial with a defined inheritance pattern. Immunodeficiency may not be a major part of the illness and may not be present in all patients; thus, these conditions differ from primary immunodeficiency syndromes, in which immune abnormalities are a consistent and prominent feature of their disease.

Congenital cytopenias and bone marrow failure syndromes

Congenital bone marrow failure syndromes (CBMFS) are extremely uncommon diseases that can present in the neonate. The objective of this article is to review the presentation, diagnosis, pathophysiology, and management of CBMFS in relation to neonatology. CBMFS should be considered when a single or multiple blood cell lineages are low secondary to failure of production. Diagnosis in the neonatal period requires a high index of suspicion. In this particular age group, CBMFS should be considered when the neonate has a family history of CBMFS, is small for gestational age, or has other physical abnormalities. History and physical examination can lead to the diagnosis. CBMFS are often associated with a predisposition to cancer later in life.

A Griscelli syndrome type 2 murine model of hemophagocytic lymphohistiocytosis (HLH)

Griscelli syndrome type 2 is caused by mutations in the RAB27A gene and is a rare and potentially fatal immune disorder associated with hemophagocytic lymphohistiocytosis (HLH). Animal models could provide assistance for better understanding the mechanisms and finding new treatments. Rab27a-deficient (ashen) mice do not spontaneously develop HLH. When injected with lymphocytic choriomeningitis virus (LCMV) strain WE, Rab27a-deficient C57BL/6 mice developed wasting disease, hypothermia, splenomegaly, cytopenia (anemia, neutropenia and thrombocytopenia), hypertriglyceridemia and increased levels of IFN-gamma, TNF-alpha, GM-CSF, IL-12, CCL5 and IL-10. Activated macrophages with hemophagocytosis were found in liver sections of these mice. Compared with perforin-deficient mice, LCMV-infected Rab27a-deficient mice showed a substantially better survival rate and slightly higher viral doses were needed to trigger HLH in Rab27a-deficient mice. This study demonstrates that LCMV-infected Rab27a-deficient C57BL/6 mice develop features consistent with HLH and, therefore, represent a murine model of HLH in human Griscelli syndrome type 2.

Role of Myosin Va in the plasticity of the vertebrate neuromuscular junction in vivo

Background

Myosin Va is a motor protein involved in vesicular transport and its absence leads to movement disorders in humans (Griscelli and Elejalde syndromes) and rodents (e.g. dilute lethal phenotype in mice). We examined the role of myosin Va in the postsynaptic plasticity of the vertebrate neuromuscular junction (NMJ).

Methodology/Principal Findings

Dilute lethal mice showed a good correlation between the propensity for seizures, and fragmentation and size reduction of NMJs. In an aneural C2C12 myoblast cell culture, expression of a dominant-negative fragment of myosin Va led to the accumulation of punctate structures containing the NMJ marker protein, rapsyn-GFP, in perinuclear clusters. In mouse hindlimb muscle, endogenous myosin Va co-precipitated with surface-exposed or internalised acetylcholine receptors and was markedly enriched in close proximity to the NMJ upon immunofluorescence. In vivo microscopy of exogenous full length myosin Va as well as a cargo-binding fragment of myosin Va showed localisation to the NMJ in wildtype mouse muscles. Furthermore, local interference with myosin Va function in live wildtype mouse muscles led to fragmentation and size reduction of NMJs, exclusion of rapsyn-GFP from NMJs, reduced persistence of acetylcholine receptors in NMJs and an increased amount of punctate structures bearing internalised NMJ proteins.

Conclusions/Significance

In summary, our data show a crucial role of myosin Va for the plasticity of live vertebrate neuromuscular junctions and suggest its involvement in the recycling of internalised acetylcholine receptors back to the postsynaptic membrane.

Rab27a regulates exocytosis of tertiary and specific granules in human neutrophils

The correct mobilization of cytoplasmic granules is essential for the proper functioning of human neutrophils in host defense and inflammation. In this study, we have found that human peripheral blood neutrophils expressed high levels of Rab27a, whereas Rab27b expression was much lower. This indicates that Rab27a is the predominant Rab27 isoform present in human neutrophils. Rab27a was up-regulated during neutrophil differentiation of HL-60 cells. Subcellular fractionation and immunoelectron microscopy studies of resting human neutrophils showed that Rab27a was mainly located in the membranes of specific and gelatinase-enriched tertiary granules, with a minor localization in azurophil granules. Rab27a was largely absent from CD35-enriched secretory vesicles. Tertiary and specific granule-located Rab27a population was translocated to the cell surface upon neutrophil activation with PMA that induced exocytosis of both tertiary and specific granules. Specific Abs against Rab27a inhibited Ca(2+) and GTP-gamma-S activation and PMA-induced exocytosis of CD66b-enriched tertiary and specific granules in electropermeabilized neutrophils, whereas secretion of CD63-enriched azurophil granules was scarcely affected. Human neutrophils lacked or expressed low levels of most Slp/Slac2 proteins, putative Rab27 effectors, suggesting that additional proteins should act as Rab27a effectors in human neutrophils. Our data indicate that Rab27a is a major component of the exocytic machinery of human neutrophils, modulating the secretion of tertiary and specific granules that are readily mobilized upon neutrophil activation.

Griscelli syndrome type 2: a rare and lethal disorder

Griscelli syndrome is a rare autosomal recessive disorder. It is characterized by pigment dilution and variable immune deficiency leading to increased susceptibility to certain infections and a tendency to develop a life-threatening hemophagocytic syndrome known as the accelerated phase. Griscelli syndrome is now classified into 3 types based on the genetic and molecular features. Primary neurological presentation without the accelerated phase is rare in type 2. In this article, the authors report a boy who was presented with seizures and diffuse white matter involvement unaccompanied by the other features of the accelerated phase. Mutation analysis in family members revealed the presence of a missense mutation in Rab27a gene. In addition to the rare presentation, this is the first case of Griscelli syndrome to be reported from Jordan.

Enhanced expression of Rab27A gene by breast cancer cells promoting invasiveness and the metastasis potential by secretion of insulin-like growth factor-II

In addition to the functions of transporting melanosome in melanocytes and releasing contents of lytic granules in CTLs, Rab27A was recently shown to be involved in exocytosis of insulin and chromaffin granules in endocrine cells; it was also reported to be expressed in an exceptionally broad range of specialized secretory cells. As autocrine and paracrine cytokines are essential for invasion and metastasis in some solid tumors, blocking them may be an effective strategy to prevent tumor dissemination. In the present study, we show that Rab27A is associated with invasive and metastatic potentials of human breast cancer cells. The overexpression of Rab27A protein redistributed the cell cycle and increased the invasive and metastatic abilities in breast cancer cells both in vitro and in vivo. We also certified that Rab27A conferred the invasive and metastatic phenotypes on breast cancer cells by promoting the secretion of insulin-like growth factor-II (IGF-II), which regulates the expression of p16, vascular endothelial growth factor, matrix metalloproteinase-9, cathepsin D, cyclin D1, and urokinase-type plasminogen activator. These data provide functional evidence that Rab27A acts as a novel mediator of invasion and metastasis promotion in human breast cancer cells, at least in part, through regulating the secretion of IGF-II, suggesting that synergistic suppression of Rab27A and IGF-II activities holds a promise for preventing breast cancer invasion and metastasis.

A novel missense mutation (G43S) in the switch I region of Rab27A causing Griscelli syndrome

The autosomal recessive Griscelli syndrome type II (GSII) is caused by mutations in the RAB27A gene. Typical clinical features include immunological impairment, silver-gray scalp hair, eyelashes and eyebrows and hypomelanosis of the skin. Rabs help determine the specificity of membrane trafficking steps within cells. In melanocytes, the GTP-bound form of Rab27A associates with the membranes of mature fully-pigmented melanosomes through its geranylgeranyl group. Once attached, Rab27A recruits the downstream effector Melanophilin (Mlph) and the actin-dependent motor protein Myosin Va (MyoVa). The molecular Rab27A/Mlph/MyoVA tripartite complex, which links melanosomes to the peripheral actin network, is required to achieve melanosome transfer to surrounding keratinocytes in the epidermis. Here we report a novel homozygous missense mutation c.127G>A, p.G43S in exon 2 of the RAB27A gene of an Afghani GSII patient. Laser scanning confocal microscopy showed that the G43S mutation, which is located in the highly conserved switch I region of Rab27A, induces perinuclear localization of melanosomes in normal melanocytes, and fails to restore melanosomes to the actin-rich periphery in GSII melanocytes. Co-immunoprecipitation studies showed that Rab27A(G43S) fails to interact with its effector Melanophilin, indicating that the switch I region functions in the recruitment of Rab effector proteins.

Analysis of RAB27A gene in griscelli syndrome type 2: novel mutations including a deletion hotspot

INTRODUCTION

Griscelli syndrome type 2 is an autosomal recessive disorder characterized by pigmentary dilution and occurrence of acute phases of hemophagocytosis. The disease is caused by mutations in RAB27A gene, coding a small GTPase involved in terminal phases of cytotoxic granule/melanosome exocytosis.

MATERIALS AND METHODS

We describe the result of mutation analysis among nine patients from seven non-related Persian families. We present four novel mutations including a deletion hot spot (514del 5).

CONCLUSION

This hot spot is flanked by "direct repeats" of nucleotides, which are previously shown to be associated with areas of recurrent small deletions.

Genetic heterogeneity in severe congenital neutropenia: how many aberrant pathways can kill a neutrophil?

PURPOSE OF REVIEW

Severe congenital neutropenia is a primary immunodeficiency in which lack of neutrophils causes inadequate innate immune host response to bacterial infections. Severe congenital neutropenia occurs with sporadic, autosomal dominant, autosomal recessive and X-linked recessive inheritance, as well as in a variety of multisystem syndromes. A principal stimulus for this review is the identification of novel genetic defects and pathophysiological insights into the role of neutrophil apoptosis.

RECENT FINDINGS

The recent findings include identification of mutations in HAX1 in autosomal recessive severe congenital neutropenia (Kostmann disease), a large epidemiological study estimating the risk of progression from severe congenital neutropenia to leukemia, a better understanding of how heterozygous mutations in neutrophil elastase (ELA2) cause severe congenital neutropenia, molecular characterization of a novel syndromic form of severe congenital neutropenia called p14 deficiency and new animal models for several syndromic forms of severe congenital neutropenia.

SUMMARY

We consider the numerous genes mutated in severe congenital neutropenia, the many attempts to make animal models of severe congenital neutropenia, and the results from both human and mouse studies investigating the molecular mechanisms of neutrophil apoptosis. Investigations of how severe congenital neutropenia genes and apoptosis pathways are connected should lead to a better understanding of the pathogenesis of neutropenia and apoptosis pathways relevant to many cell types.

Clinical and microscopic hair features of griscelli syndrome associated with asymmetric crying facies in an infant

Griscelli syndrome (GS) is a rare autosomal recessive disorder characterized by immunodeficiency and partial albinism. Asymmetric crying facies (ACF) is caused by congenital hypoplasia or agenesis of the depressor anguli oris muscle. Asymmetric crying facies may be isolated or it may be associated with various anomalies. We report a 3-month-old Turkish boy who had clinical and microscopic hair features of GS associated with ACF. To the best of our knowledge, this is the 1st case of this association to be reported in the literature.

The zebrafish mutant lbk/vam6 resembles human multisystemic disorders caused by aberrant trafficking of endosomal vesicles

The trafficking of intracellular vesicles is essential for a number of cellular processes and defects in this process have been implicated in a wide range of human diseases. We identify the zebrafish mutant lbk as a novel model for such disorders. lbk displays hypopigmentation of skin melanocytes and the retinal pigment epithelium (RPE), an absence of iridophore reflections, defects in internal organs (liver, intestine) as well as functional defects in vision and the innate immune system (macrophages). Positional cloning, an allele screen, rescue experiments and morpholino knock-down reveal a mutation in the zebrafish orthologue of the vam6/vps39 gene. Vam6p is part of the HOPS complex, which is essential for vesicle tethering and fusion. Affected cells in the lbk RPE, liver, intestine and macrophages display increased numbers and enlarged intracellular vesicles. Physiological and behavioural analyses reveal severe defects in visual ability in lbk mutants. The present study provides the first phenotypic description of a lack of vam6 gene function in a multicellular organism. lbk shares many of the characteristics of human diseases and suggests a novel disease gene for pathologies associated with defective vesicle transport, including the arthrogryposis-renal dysfunction-cholestasis (ARC) syndrome, the Hermansky-Pudlak syndrome, the Chediak-Higashi syndrome and the Griscelli syndrome.

Development of in situ melanoma after allogeneic bone marrow transplantation in Griscelli syndrome type II

GS is an uncommon autosomal recessive disorder characterized by pigmentary dilution of the skin and hair and in most patients by abnormal regulation of the immune system. Childhood melanoma is rare in the pediatric population. The best prognosis is achieved with early diagnosis and definitive surgical excision of melanoma. We report a case of a patient with GS type II and melanoma who was successfully treated by allogeneic bone marrow transplantation and surgical excision of the melanoma.

A molecular classification of congenital neutropenia syndromes

Current knowledge on the molecular pathogenesis of severe congenital neutropenia indicates that the clinical diagnosis includes a heterogeneous group of disorders following different patterns of inheritance. Similarly, multifaceted syndromes associated with neutropenia can be classified molecularly, which in turn allows for a better understanding of the basis of the neutropenia. Many of the neutropenia disorders can be treated with G-CSF (filgrastim) to increase the neutrophil count, thereby reducing infection morbidity and mortality. In some instances hematopoietic stem cell transplantation remains the only curative treatment currently available. This review describes and classifies, on a molecular basis, both primary congenital neutropenia and multifaceted syndromes associated with neutropenia.

Griscelli syndrome: a case report

A 10-year-old boy presented with partial albinism and typical clinical features of a macrophage activation syndrome (hepatosplenomegaly, fever, and pancytopenia), suggesting the diagnosis of Griscelli syndrome. The diagnosis was confirmed by light microscopic evaluation of hair that showed characteristic large aggregates of pigment granules irregularly distributed along the hair shaft. Immunosuppressive therapy controlled his macrophage activation syndrome successfully. Since early diagnosis is life saving and simple methods confirm the diagnosis, finding of partial albinism in children should alert clinicians to consider Griscelli syndrome.

Hypomelanotic Conditions of the Newborn and Infant

Depigmented nevi, pityriasis alba, and postinflammatory hypopigmentation are the most frequent hypomelanotic conditions in newborns and infants. These, and examples of less frequent hypopigmentations are briefly discussed in this article. A new classification for depigmented nevi is also proposed.

Griscelli syndrome

The dermatology staff was called to evaluate abnormal hair on a 22-month-old Hispanic girl whose parents were first cousins. Her medical history was significant for leptomeningitis with subsequent neurologic devastation, gastroesophageal reflux disease, and recurrent respiratory infections. Her hospital course was complicated by sepsis, liver dysfunction, pan-cytopenia, and disseminated intravascular coagulation. She had developed normally for the first year of life. At 13 months she became progressively lethargic and developed floppy muscle tone; a delay in mental and motor milestones was recognized. Results of a metabolic workup were negative. On examination she was noted to have generalized excessively fair skin when compared with her parents. She had silver-gray hair (Figure 1) and white eyebrows and body hair. Her maternal grandfather and granduncles had silver hair since childhood, but were without health problems. A maternal family member was said to have light skin. The presumed diagnosis before pathologic examination was Chediak-Higashi syndrome. Hematoxylin and eosin stain tests revealed prominent melanocytes in the basal layer of the epidermis. The melanocytes were large and distended with a large volume of melanin (Figure 2). The adjacent keratinocytes were completely devoid of melanin. Application of Masson-Fontana ammoniac silver stain highlighted prominent melanocytic melanin and a relative paucity of melanin in the adjacent keratinocytes (Figure 3). Microscopic examination of her hair revealed clumps of melanin of various sizes and shapes irregularly distributed throughout the hair shaft. Ultrastructural examination of the epidermis showed the melanocytes were distended by an accumulation of large stage IV mature melanosomes. Peripheral blood smear failed to show abnormal granules, even after repeated examination. Based on the clinical features and the pathologic findings, a diagnosis of Griscelli syndrome type 2 was made.

Neurological presentation of Griscelli syndrome: obstructive hydrocephalus without haematological abnormalities or organomegaly

Griscelli syndrome is a rare autosomal-recessive disorder characterised by partial albinism, immunodeficiency, organomegaly and accelerated phases. During accelerated phases, pancytopenia, haemophagocytosis, hypoproteinemeia occur which may be accompanied by neurological deterioration. Primary neurological presentation is rare and we report a case that presented with obstructive hydrocephalus and infiltrative lesions in the brain unaccompanied by other features of accelerated phase. Biopsy of these lesions demonstrated sinus histiocytosis. Electron microscopy of hair shaft and genetic studies established the diagnosis of Griscelli disease with RAB 27A mutation.

Rab27a is a key component of the secretory machinery of azurophilic granules in granulocytes

Neutrophils kill micro-organisms using microbicidal products that they release into the phagosome or into the extracellular space. The secretory machinery utilized by neutrophils is poorly characterized. We show that the small GTPase Rab27a is an essential component of the secretory machinery of azurophilic granules in granulocytes. Rab27a-deficient mice have impaired secretion of MPO (myeloperoxidase) into the plasma in response to lipopolysaccharide. Cell fractionation analysis revealed that Rab27a and the Rab27a effector protein JFC1/Slp1 (synaptotagmin-like protein 1) are distributed principally in the low-density fraction containing a minor population of MPO-containing granules. By immunofluorescence microscopy, we detected Rab27a and JFC1/Slp1 in a minor subpopulation of MPO-containing granules. Interference with the JFC1/Slp1-Rab27a secretory machinery impaired secretion of MPO in permeabilized neutrophils. The expression of Rab27a was dramatically increased when promyelocytic HL-60 cells were differentiated into granulocytes but not when they were differentiated into monocytes. Down-regulation of Rab27a in HL-60 cells by RNA interference did not affect JFC1/Slp1 expression but significantly decreased the secretion of MPO. Neither Rab27a nor JFC1/Slp1 was integrated into the phagolysosome membrane during phagocytosis. Neutrophils from Rab27a-deficient mice efficiently phagocytose zymosan opsonized particles and deliver MPO to the phagosome. We conclude that Rab27a and JFC1/Slp1 permit MPO release into the surrounding milieu and constitute key components of the secretory machinery of azurophilic granules in granulocytes. Our results suggest that the granules implicated in cargo release towards the surrounding milieu are molecularly and mechanistically different from those involved in their release towards the phagolysosome.

NK cytotoxicity mediated by CD16 but not by NKp30 is functional in Griscelli syndrome

Griscelli syndrome (GS) type 2 is an autosomal recessive disorder represented by pigment dilution and impaired cytotoxic T lymphocyte (CTL) activity. NK activity has been scarcely investigated in GS patients. Here, we describe a new patient, possessing a hemophagocytic syndrome with a homozygous Q118X nonsense RAB27A mutation. Single specific primer–polymerase chain reaction (SSP-PCR) was developed based on this mutation and is currently used in prenatal genetic analysis. As expected, CTLs in the patient are not functional and NK cytotoxicity against K562 or 721.221 cells is diminished. Surprisingly, however, we demonstrate that CD16-mediated killing is intact in this patient and is therefore RAB27A independent, whereas NKp30-mediated killing is impaired and is therefore RAB27A dependent. We further analyzed the signaling pathways of these 2 receptors and demonstrated phosphorylation of Vav1 after CD16 activation but not after NKp30 engagement. Thus, we identify a novel homozygous mutation in the RAB27A gene of a new GS patient, observe for the first time that some activating NK receptors function in GS patients, and demonstrate a functional dichotomy in the killing mediated by these human NK-activating receptors.

Perforin-mediated target-cell death and immune homeostasis

The granule exocytosis pathway of cytotoxic lymphocytes is crucial for immune surveillance and homeostasis. The trafficking of granule components, including the membrane-disruptive protein perforin, to the immunological synapse leads to the delivery of granule proteases (granzymes) into the target cell and its destruction through apoptosis. Several independent molecular abnormalities associated with defects of either granule trafficking or perforin function can cause cytotoxic lymphocyte dysfunction. In humans, inherited perforin mutations result in severe immune dysregulation that manifests as familial haemophagocytic lymphohistiocytosis. This Review describes recent progress in defining the structure, function, biochemistry and cell biology of perforin.

Griscelli syndrome

A 4-month-old child had silvery gray hair, light-colored skin, recurrent chest infections, hepatosplenomegaly, and episodes of pancytopenia and hemophagocytosis in the liver, spleen, and bone marrow. Light microscopy of hair showed characteristic large aggregates of pigment granules distributed irregularly along the hair shaft. Peripheral blood smear examination did not show giant granules in granulocytes. Enlarged hyperpigmented basal melanocytes with sparsely pigmented adjacent keratinocytes were seen on the skin biopsy specimen. On the basis of these clinical and laboratory findings, Griscelli syndrome was diagnosed. The child succumbed to infection during an accelerated phase of the disease.

Polarized light microscopy of hair shafts aids in the differential diagnosis of Chédiak-Higashi and Griscelli-Prunieras syndromes

PURPOSE

To study and compare the appearance of hairs from patients with Chédiak-Higashi and Griscelli-Prunieras syndromes under light and polarized light microscopy.

METHOD

Hairs from 2 Chédiak-Higashi and 2 Griscelli-Prunieras patients were obtained and examined under normal and polarized light microscopy.

RESULTS

Under light microscopy, hairs from Chédiak-Higashi patients presented evenly distributed, regular melanin granules, larger than those seen in normal hairs. Under polarized light microscopy, shafts exhibited a bright and polychromatic refringence appearance. In contrast, hair from Griscelli-Prunieras patients, under light microscopy, exhibited bigger and irregular melanin granules, distributed mainly near the medulla. Under polarized light microscopy, shafts appeared monotonously white.

CONCLUSION

Light microscopic examination of hair shafts of patients with Chédiak-Higashi or Griscelli-Prunieras syndrome reveals subtle differences that are useful in identifying both disorders, but not in distinguishing between them. We provide evidence that polarized light microscopy of hair shafts, an approach that has not been previously described, aids in differentiating between these syndromes. We propose hair study by polarized light microscopy as a helpful complementary diagnostic method for differential diagnosis between CHS and GPS, especially when the more sophisticated molecular studies are not available.

Bilateral basal ganglia involvement in a patient with Griscelli syndrome

We report a 6-year-old Iranian boy with silvery-gray hair, eyelashes and the eyebrows who was admitted because of seizures and subsequent stupor. He had previous history of acute hemiparesis at 1 year of age and hepatitis-like syndrome 3 months ago. Microscopic examination of the patient's hair shaft revealed different sized clumps of melanin seen in the center of the shafts. Bone marrow aspiration revealed erythroid hyperplasia and erythrophagocytic cells. Bilateral frontal cortical and subcortical high signal lesions, dirty white matter, high signal areas in the upper pons and in both caudates and lentiform nuclei in T2 WI were the brain MRI findings of the patient. He died in the accelerated phase of Griscelli Syndrome (GS) type 2. To our knowledge we report the first case of GS from Iran.

Black hair follicular dysplasia in Large Münsterländer dogs: clinical, histological and ultrastructural features

Four Large Münsterländer cross-bred dogs affected with black hair follicular dysplasia (BHFD) and one unaffected control littermate were observed, and skin was sampled weekly over the first 19 weeks of life. Affected dogs were born with silvery grey hair, a consequence of melanin clumping in the hair shafts. Hair bulb melanocytes were densely pigmented, and contained abundant stage IV melanosomes but adjacent matrix keratinocytes lacked melanosomes. Melanin clumping was not prominent in epidermal melanocytes in the haired skin but occurred in the foot pads. Follicular changes progressed from bulbar clumping, clumping in the isthmus/infundibulum and finally to dysplastic hair shafts. Alopecia developed progressively in pigmented areas. Silver-grey hair, melanin clumping, accumulation of stage IV melanosomes within melanocytes and insufficient melanin transfer to adjacent keratinocytes are also classic features of human Griscelli syndrome. The underlying cause in Griscelli syndrome is a defect of melanocytic intracellular transport proteins leading to inadequate and disorganized melanosome transfer to keratinocytes with resultant melanin clumping. In view of the correlation in the phenotype, histology and ultrastructure between both disorders, a defect in intracellular melanosome transport is postulated as the pathogenic mechanism in BHFD.

Griscelli syndrome: description of a case with Rab27A mutation

A 7-month-old Turkish boy presented with partial albinism and typical clinical features of an accelerated phase, suggesting the diagnosis of Griscelli syndrome. The diagnosis was confirmed by light microscopic evaluation of hair and a peripheral blood smear. Genetic analysis identified a mutation in the Rab27A gene. He was initiated immunosuppressive treatment but accelerated phase could not be ameliorated. He unfortunately died from multiorgan failure. The finding of partial albinism in children should alert clinicians to consider Griscelli syndrome since simple methods can confirm the diagnosis and early diagnosis is life-saving.

Mechanisms of Disordered Granulopoiesis in Congenital Neutropenia

Neutrophils are critical components of the innate immune response, and persistent neutropenia is associated with a marked susceptibility to infection. There are a number of inherited clinical syndromes in which neutropenia is a prominent feature. A study of these rare disorders has provided insight into the mechanisms regulating normal neutrophil homeostasis. Tremendous progress has been made at defining the genetic basis of these disorders. Herein, progress in understanding the genetic basis and molecular mechanisms of these disorders is discussed. We have focused our discussion on inherited disorders in which neutropenia is the sole or major hematopoietic defect.

Pediatric hemophagocytic syndromes: a diagnostic and therapeutic challenge

Pediatric hemophagocytic syndrome (HS) is a severe and often fatal clinical disorder. This syndrome is frequently unrecognized, and thus, affected children may receive suboptimal management, leading to an increase in mortality. The purpose of this review is to provide a clinical guide to (1) the recognition of HS based on clinical, biologic, and pathologic features; (2) the identification of the primary cause of HS in a given affected child; and (3) the initiation of effective treatment in a timely manner.

Primary hemophagocytic syndromes point to a direct link between lymphocyte cytotoxicity and homeostasis

Hemophagocytic syndrome (HS) is a severe and often fatal syndrome resulting from potent and uncontrolled activation and proliferation of T-lymphocytes, leading to excessive macrophage activation and multiple deleterious effects. The onset of HS characterizes several inherited disorders in humans. In each condition, the molecular defect impairs the granule-dependent cytotoxic activity of lymphocytes, thus highlighting the determinant role of this function in driving the immune system to a state of equilibrium following infection. It has also been shown that some of the proteins required for lytic granule secretion are required for melanocyte function, leading to associated hypopigmentation in these conditions. This review focuses on several effectors of this secretory pathway, recently identified, because their defects cause these disorders, and discusses their role and molecular interactions in granule-dependent cytotoxic activity.

Griscelli syndrome: characterization of a new mutation and rescue of T-cytotoxic activity by retroviral transfer of RAB27A gene

Griscelli syndrome (GS) is caused by mutations in the MYO5A (GS1), RAB27A (GS2), or MLPH (GS3) genes, all of which lead to a similar pigmentary dilution. In addition, GS1 patients show primary neurological impairment, whereas GS2 patients present immunodeficiency and periods of lymphocyte proliferation and activation, leading to their infiltration in many organs, such as the nervous system, causing secondary neurological damage. We report the diagnosis of GS2 in a 4-year-old child with haemophagocytic syndrome, immunodeficiency, and secondary neurological disorders. Typical melanosome accumulation was found in skin melanocytes and pigment clumps were observed in hair shafts. Two heterozygous mutant alleles of the RAB27A gene were found, a C-T transition (C352T) that leads to Q118stop and a G-C transversion on the exon 5 splicing donor site (G467+1C). Functional assays showed increased cellular activation and decreased cytotoxic activity of NK and CD8+ T cells, associated with defective lytic granules release. Myosin-Va expression and localization in the patient lymphocytes were also analyzed. Most importantly, we show that cytotoxic activity of the patient's CD8+ T lymphocytes can be rescued in vitro by RAB27A gene transfer mediated by a recombinant retroviral vector, a first step towards a potential treatment of the acute phase of GS2 by RAB27A transduced lymphocytes.

Syndromic immunodeficiencies: genetic syndromes associated with immune abnormalities

In syndromic immunodeficiencies, clinical features not directly associated with the immune defect are prominent. Patients may present with either infectious complications or extra-immune medical issues. In addition to the immunologic abnormality, a wide range of organ systems may be affected. Patients may present with disturbances in skeletal, neurologic, dermatologic, or gastrointestinal function or development. These conditions can be caused by developmental abnormalities, chromosomal aberrations, metabolic disorders, or teratogens. For a number of these conditions, recent advances have resulted in an enhanced understanding of their genetic basis. The finding of immune deficits in a number of defined syndromes with congenital anomalies suggests that an underlying genetic syndrome should be considered in those patients in whom a significant non-immune feature is present.

Griscelli syndrome

An eight month old male infant presented with recurrent infections and partial albinism. Initially a possibility of Chediak Higashi syndrome (CHS) was considered, but a negative investigative work up prompted us to look for an alternate diagnosis. A literature search revealed that Griscelli syndrome (GS) has overlapping symptoms and signs. The findings in skin and hair biopsies in Griscelli syndrome are distinctive.

Rab proteins and endocytic trafficking: potential targets for therapeutic intervention

Rab GTPases serve as master regulators of vesicular membrane transport on both the exo- and endocytic pathways. In their active forms, rab proteins serve in cargo selection and as scaffolds for the sequential assembly of effectors requisite for vesicle budding, cytoskeletal transport, and target membrane fusion. Rab protein function is in turn tightly regulated at the level of protein expression, localization, membrane association, and activation. Alterations in the rab GTPases and associated regulatory proteins or effectors have increasingly been implicated in causing human disease. Some diseases such as those resulting in bleeding and pigmentation disorders (Griscelli syndrome), mental retardation, neuropathy (Charcot-Marie-Tooth), kidney disease (tuberous sclerosis), and blindness (choroideremia) arise from direct loss of function mutations of rab GTPases or associated regulatory molecules. In contrast, in a number of cancers (prostate, liver, breast) as well as vascular, lung, and thyroid diseases, the overexpression of select rab GTPases have been tightly correlated with disease pathogenesis. Unique therapeutic opportunities lie ahead in developing strategies that target rab proteins and modulate the endocytic pathway.

Lytic granules, secretory lysosomes and disease

Lytic granules harbour many of the dangerous apoptosis-inducing molecules of the immune system, including perforin, granzymes and Fas ligand. Safe transport, storage and release of these lytic components is vital. As a secretory lysosome, the lytic granule is able to accomplish these roles, as well as conferring the lysosomal functions of cytotoxic T lymphocytes and natural killer cells. Secretory lysosomes are common to many other haemopoietic cells and also melanocytes. Many of the proteins used in lysosomal secretion are found in both melanocytes and hemopoietic cells, and are dysfunctional in genetic diseases with defects in these proteins. The genetically heterogeneous Hermansky-Pudlak syndrome represents an excellent model for revealing proteins involved in secretory lysosome functioning. However, studies of this disease reveal differences between the various different types of secretory lysosomes, including lytic granules.

The actin-binding domain of Slac2-a/melanophilin is required for melanosome distribution in melanocytes

Melanosomes containing melanin pigments are transported from the cell body of melanocytes to the tips of their dendrites by a combination of microtubule- and actin-dependent machinery. Three proteins, Rab27A, myosin Va, and Slac2-a/melanophilin (a linker protein between Rab27A and myosin Va), are known to be essential for proper actin-based melanosome transport in melanocytes. Although Slac2-a directly interacts with Rab27A and myosin Va via its N-terminal region (amino acids 1 to 146) and the middle region (amino acids 241 to 405), respectively, the functional importance of the putative actin-binding domain of the Slac2-a C terminus (amino acids 401 to 590) in melanosome transport has never been elucidated. In this study we showed that formation of a tripartite protein complex between Rab27A, Slac2-a, and myosin Va alone is insufficient for peripheral distribution of melanosomes in melanocytes and that the C-terminal actin-binding domain of Slac2-a is also required for proper melanosome transport. When a Slac2-a deletion mutant (DeltaABD) or point mutant (KA) that lacks actin-binding ability was expressed in melanocytes, the Slac2-a mutants induced melanosome accumulation in the perinuclear region, possibly by a dominant negative effect, the same as the Rab27A-binding-defective mutant of Slac2-a or the myosin Va-binding-defective mutant. Our findings indicate that Slac2-a organizes actin-based melanosome transport in cooperation with Rab27A, myosin Va, and actin.

Griscelli syndrome restricted to hypopigmentation results from a melanophilin defect (GS3) or a MYO5A F-exon deletion (GS1)

Griscelli syndrome (GS) is a rare autosomal recessive disorder that associates hypopigmentation, characterized by a silver-gray sheen of the hair and the presence of large clusters of pigment in the hair shaft, and the occurrence of either a primary neurological impairment or a severe immune disorder. Two different genetic forms, GS1 and GS2, respectively, account for the mutually exclusive neurological and immunological phenotypes. Mutations in the gene encoding the molecular motor protein Myosin Va (MyoVa) cause GS1 and the dilute mutant in mice, whereas mutations in the gene encoding the small GTPase Rab27a are responsible for GS2 and the ashen mouse model. We herein present genetic and functional evidence that a third form of GS (GS3), whose expression is restricted to the characteristic hypopigmentation of GS, results from mutation in the gene that encodes melanophilin (Mlph), the ortholog of the gene mutated in leaden mice. We also show that an identical phenotype can result from the deletion of the MYO5A F-exon, an exon with a tissue-restricted expression pattern. This spectrum of GS conditions pinpoints the distinct molecular pathways used by melanocytes, neurons, and immune cells in secretory granule exocytosis, which in part remain to be unraveled.