Griscelli syndrome: description of a case with Rab27A mutation

Hemophagocytic lymphohistiocytosis after solid organ transplantation: A challenge for clinicians

Hemophagocytic lymphohistiocytosis (HLH) is a rare inflammatory disorder with a high mortality rate and a wide range of symptoms. Solid organ transplantation, which provides patients with a unique immunosuppressive state, is a less common predisposing factor for HLH. HLH after solid organ transplantation (HLH-SOT) is very rare and fatal. It is hard to diagnose and treat and extremely understudied. The use of immunosuppressants makes the situation of HLH-SOT more complex. This review summarizes the existing literature on HLH after solid organ transplantation and describes its triggers and symptoms, focusing on its diagnosis and treatment. We performed a literature search of case reports, case series, letters to the editor, and clinical quizzes describing patients with HLH after solid organ transplantation (HLH-SOT). We provide recommendations on the diagnosis protocol and treatment strategy based on the existing evidence.

Identification of MicroRNA Targeting Mlph and Affecting Melanosome Transport

Melanosomes undergo a complex maturation process and migrate into keratinocytes. Melanophilin (Mlph), a protein complex involving myosin Va (MyoVa) and Rab27a, enables the movement of melanosomes in melanocytes. In this study, we found six miRNAs targeting Mlph in mouse using two programs (http://targetscan.org and DianaTools). When melan-a melanocytes were treated with six synthesized microRNAs, miR-342-5p, miR-1839-5p, and miR-3082-5p inhibited melanosome transport and induced melanosome aggregation around the nucleus. The other microRNAs, miR-5110, miR-3090-3p, and miR-186-5p, did not inhibit melanosome transport. Further, miR-342-5p, miR-1839-5p, and miR-3082-5p decreased Mlph expression. The effect of miR-342-5p was the strongest among the six synthesized miRNAs. It inhibited melanosome transport in melan-a melanocytes and reduced Mlph expression in mRNA and protein levels in a dose-dependent manner; however, it did not affect Rab27a and MyoVa expressions, which are associated with melanosome transport. To examine miR-342-5p specificity, we performed luciferase assays in a mouse melanocyte-transfected reporter vector including Mlph at the 3′-UTR (untranslated region). When treated with miR-342-5p, luciferase activity that had been reduced by approximately 50% was restored after inhibitor treatment. Therefore, we identified a novel miRNA affecting Mlph and melanosome transport, and these results can be used for understanding Mlph expression and skin pigmentation regulation.

Congenital hemophagocytic lymphohistiocytosis presenting as thrombocytopenia in a newborn

Hemophagocytic lymphohistiocytosis (HLH) is a disease caused by dysregulation and hyperactivation of the immune system, and can be familial or acquired. HLH presenting in infancy can be rapidly fatal if not promptly recognized and treated. Congenital HLH can be caused by various genetic mutations or part of immunodeficiency syndromes. We present an infant with Griscelli syndrome and familial HLH with atypical genetic mutations, presenting as thrombocytopenia on the first day of life, cured with chemotherapy and unrelated cord blood transplant.

Advances in understanding the pathogenesis of HLH

Haemophagocytic lymphohistiocytosis (HLH) is a hyperinflammatory disorder resulting from immune dysfunction reflecting either primary immune deficiency or acquired failure of normal immune homeostasis. Familial HLH includes autosomal recessive and X-linked disorders characterized by uncontrolled activation of T cells and macrophages and overproduction of inflammatory cytokines, secondary to defects in genes encoding proteins involved in granule-dependent cytolytic pathways. In older children and adults, HLH is associated more often with infections, malignancies, autoimmune diseases, and acquired immune deficiencies. HLH, macrophage activation syndrome, sepsis, and systemic inflammatory response syndrome are different clinical entities that probably represent a common immunopathological state, termed cytokine storm. These conditions may be clinically indistinguishable; all include massive inflammatory response, elevated serum cytokine levels, multi-organ involvement, haemophagocytic macrophages, and often death. Tissues of haematopoietic and lymphoid function are directly involved; other organs are secondarily damaged by circulating cytokines and chemokines. Haemophagocytic disorders are now increasingly diagnosed in the context of severe inflammatory reactions to viruses, malignancies and systemic connective tissue diseases. Many of these cases may reflect underlying genetic predispositions to HLH. The detection of gene defects has contributed considerably to our understanding of HLH, but the mechanisms leading to acquired HLH have yet to be fully determined.

Clinical presentation of Griscelli syndrome type 2 and spectrum of RAB27A mutations

BACKGROUND

Griscelli syndrome type 2 (GS2) is an autosomal-recessive immunodeficiency caused by mutations in RAB27A, clinically characterized by partial albinism and haemophagocytic lymphohistocytosis (HLH). We evaluated the frequency of RAB27A mutations in 21 unrelated patients with haemophagocytic syndromes without mutations in familial HLH (FHL) causing genes or an established diagnosis of GS2. In addition, we report three patients with known GS2. Moreover, neurological involvement and RAB27A mutations in previously published patients with genetically verified GS2 are reviewed.

PROCEDURE

Mutation analysis of RAB27A was performed by direct DNA sequencing. NK cell activity was evaluated and microscopy of the hair was performed to confirm the diagnosis.

RESULTS

RAB27A mutations were found in 1 of the 21 families. This Swedish family had three affected children with heterozygous compound mutations consisting of a novel splice error mutation, [c.239G>C], and a nonsense mutation, [c.550C>T], p.R184X. The three additional children all carried homozygous RAB27A mutations, one of which is a novel splice error mutation, [c.240-2A>C]. Of note, five of the six patients displayed neurological symptoms, while three out of six patients displayed NK cell activity within normal reference values, albeit low. A literature review revealed that 67% of GS2 patients have been reported with neurological manifestations.

CONCLUSIONS

Identification of RAB27A mutations can facilitate prompt diagnosis and treatment, and aid genetic counselling and prenatal diagnosis. Since five of six patients studied herein initially were diagnosed as having FHL, we conclude that the diagnosis of GS2 may be overlooked, particularly in fair-haired patients with haemophagocytic syndromes.

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.

Pigmentary disorders in the Mediterranean area

The Mediterranean area represents the area of land that borders the Mediterranean basin. It is composed of several countries that share many geographic and racial characteristics. Although Mediterraneans seem to share common skin type and are subjected to similar enviromental factors, they still represent a genetic and socioeconomic diversity. True prevalence of pigmentary disorders in this area depends on large epidemiologic studies, including countries that are not available. This article, however, highlights and classifies the most important developmental (heritable-genetic) and acquired pigmentary disorders seen and reported in this important area of the world.