Germline CYBB mutations that selectively affect macrophages in kindreds with X-linked predisposition to tuberculous mycobacterial disease

Germline mutations in CYBB, the human gene encoding the gp91(phox) subunit of the phagocyte NADPH oxidase, impair the respiratory burst of all types of phagocytes and result in X-linked chronic granulomatous disease (CGD). We report here two kindreds in which otherwise healthy male adults developed X-linked recessive Mendelian susceptibility to mycobacterial disease (MSMD) syndromes. These patients had previously unknown mutations in CYBB that resulted in an impaired respiratory burst in monocyte-derived macrophages but not in monocytes or granulocytes. The macrophage-specific functional consequences of the germline mutation resulted from cell-specific impairment in the assembly of the NADPH oxidase. This `experiment of nature` indicates that CYBB is associated with MSMD and demonstrates that the respiratory burst in human macrophages is a crucial mechanism for protective immunity to tuberculous mycobacteria.

Hematologically important mutations: X-linked chronic granulomatous disease (third update)

Chronic granulomatous disease (CGD) is an immunodeficiency disorder affecting about 1 in 250,000 individuals. The disease is caused by a lack of superoxide production by the leukocyte enzyme NADPH oxidase. Superoxide is used to kill phagocytosed micro-organisms in neutrophils, eosinophils, monocytes and macrophages. The leukocyte NADPH oxidase is composed of five subunits, of which the enzymatic component is gp91-phox, also called Nox2. This protein is encoded by the CYBB gene on the X chromosome. Mutations in this gene are found in about 70% of all CGD patients. This article lists all mutations identified in CYBB in the X-linked form of CGD. Moreover, apparently benign polymorphisms in CYBB are also given, which should facilitate the recognition of future disease-causing mutations. (C) 2010 Elsevier Inc. All rights reserved.

Hydrocephalus and moderate mental retardation in a boy with Van der Woude phenotype and IRF6 gene mutation

In this report, we present a boy with lower lip pits, distinct craniofacial dysmorphism with cleft lip and palate, central nervous system malformation, and severe mental retardation. Similar but less pronounced facial findings were present in his mentally normal mother and maternal grandfather, both presenting with lower lip pits. Cleft lip was present in patient's father. Analysis of the VWS1 and VWS2 regions were performed to elucidate the molecular basis of the phenotype of the propositus. Screening or mutations at the IRF6 gene detected a pathogenic mutation (c.960G > C) in the propositus and in his mother; and a single nucleotide polymorphism (c.175-5C > G) in the propositus and in his father. Clinical and genetic aspects of this case are discussed.

High frequencies of plexiform neurofibromas, mental retardation, learning difficulties, and scoliosis in Brazilian patients with neurofibromatosis type 1

A clinical study of Brazilian patients with neurofibromatosis type 1 (NF1) was performed in a multidisciplinary Neurofibromatosis Program called CEPAN (Center of Research and Service in Neurofibromatosis). Among 55 patients (60% females, 40% males) who met the NIH criteria for the diagnosis of NF1, 98% had more than six café-au-lait patches, 94.5% had axillary freckling, 45% had inguinal freckling, and 87.5% had Lisch nodules. Cutaneous neurofibromas were observed in 96%, and 40% presented plexiform neurofibromas. A positive family history of NF1 was found in 60%, and mental retardation occurred in 35%. Some degree of scoliosis was noted in 49%, 51% had macrocephaly, 40% had short stature, 76% had learning difficulties, and 2% had optic gliomas. Unexpectedly high frequencies of plexiform neurofibromas, mental retardation, learning difficulties, and scoliosis were observed, probably reflecting the detailed clinical analysis methods adopted by the Neurofibromatosis Program. These same patients were screened for mutations in the GAP-related domain/GRD (exons 20-27a) by single-strand conformation polymorphism. Four different mutations (Q1189X, 3525-3526delAA, E1356G, c.4111-1G>A) and four polymorphisms (c.3315-27G>A, V1146I, V1317A, c.4514+11C>G) were identified. These data were recently published.

Involvement of organic systems in golden retriever X-linked muscular dystrophy

Duchenne muscular dystrophy is a lethal genetic disease characterized by progressive muscle degeneration that usually had been used the Golden Retriever as a model for studying the disease (GRMD - Golden Retriever Muscular Dystrophy). A total of 16 male dystrophic Golden Retrievers dogs between 5 to 51 months of age were examined in the present study. The animals were classified as dystrophic according to two simultaneous complementary criteria: genotypic analysis and serum creatine kinase levels. The macroscopic abnormalities of the different organs and tissues and histopathological features were described using hematoxylin-eosin. The lesions in the skeletal muscles associated with the digestive problems resulted in cachexia with different intensities in all the dystrophic dogs. Cardiac muscle involvement was found in 87,5% of the GRMD dogs resulting, however, in cardiac failure in only 18,8% of the animals. The musculature of the diaphragm was hypertrophic in all affected animals resulting in progressive respiratory muscle weakness and at later stages in respiratory failure (81,25%). The liver abnormalities found in dystrophic dogs were originated mainly from heart disease and developed progressively. Hyperemia of mucosa and granular material indicated changes in the functioning and emptying of bladder. The germinative lineage cells presented moderate to severe degeneration probably due to degeneration of the scrotum and cremaster muscle which prevented the proper thermo-regulation of the testicle. Our results highlight the fact that there is significant impairment of the cardiac, respiratory and skeletal muscle systems in GRMD dogs since the age of five months. In addition, significant alterations of the gastrointestinal tract, urinary and reproductive systems are indicating the presence of degenerative lesions in the smooth musculature.

Profiles of steroid hormones in canine X-Linked muscular dystrophy via stable isotope dilution LC-MS/MS

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Atrichia, abnormal EEG, epilepsy and mental retardation in two sisters

Two daughters of a nonconsanguineous couple are described. Both present mental retardation, epileptic seizures, congenital atrichia, histologically anomalous skin and abnormal EEG pattern. From a discussion of the literature on atrichia, the forms without involvement of teeth, nails and hidrosis, among which recessive inheritance prevails, are distinguished from each other. None of them coincide with the syndrome described here.

Dendritic cells from X-linked hyper-IgM patients present impaired responses to Candida albicans and Paracoccidioides brasiliensis

Background: Patients with X-linked hyper-IgM syndrome (X-HIGM) due to CD40 ligand (CD40L) mutations are susceptible to fungal pathogens; however, the underlying susceptibility mechanisms remain poorly understood. Objective: To determine whether monocyte-derived dendritic cells (DCs) from patients with X-HIGM exhibit normal responses to fungal pathogens. Methods: DCs from patients and controls were evaluated for the expression of costimulatory (CD80 and CD86) and MHC class II molecules and for their ability to produce IL-12 and IL-10 in response to Candida albicans and Paracoccidioides brasiliensis. We also evaluated the ability of C albicans- and P brasiliensis-pulsed mature DCs to induce autologous T-cell proliferation, generation of T helper (T-H) 17 cells, and production of IFN-gamma, TGF-beta, IL-4, IL-5, and IL-17. Results: Immature DCs from patients with X-HIGM showed reduced expression of CD80, CD86, and HLA-DR, which could be reversed by exogenous trimeric soluble CD40L. Most important, mature DCs from patients with X-HIGM differentiated by coculturing DCs with fungi secreted minimal amounts of IL-12 but substantial amounts of IL-10 compared with mature DCs from normal individuals. Coculture of mature DCs from X-HIGM patients with autologous T cells led to low IFN-g production, whereas IL-4 and IL-5 production was increased. T-cell proliferation and IL-17 secretion were normal. Finally, in vitro incubation with soluble CD40L reversed the decreased IL-12 production and the skewed T-H(2) pattern response. Conclusion: Absence of CD40L during monocyte/DC differentiation leads to functional DC abnormalities, which may contribute to the susceptibility to fungal infections in patients with X-HIGM. (J Allergy Clin Immunol 2012; 129: 778-86.)

Necklace fibers as histopathological marker in a patient with severe form of X-linked myotubular myopathy

X-linked myotubular myopathy due to mutations in the MTM1 gene is classically characterized by a severe neonatal phenotype and a typical muscle biopsy presenting globular and centrally located nuclei in muscle myofibers. Recently, four patients with mild late-onset form have been described, a male with a hemizygous mutation and three females with heterozygous mutations in the MTM1 gene. The muscle biopsies were performed at 13-35 years of age and a new histological marker, the necklace fibers, was described. Here, we report two siblings with the pathogenic c.664 C > T mutation in the MTM1 gene, presenting a severe muscle weakness and respiratory impairment requiring ventilatory support since the first months of life until death, at the age of 36 months and 5 months. In the older brother the muscle biopsy, performed at the age of 30 months, showed almost 100% of necklace fibers, which were not present in the younger one submitted to muscle biopsy at 5 months of age. Our findings confirm the necklace fibers can be a histopathological finding of MTM1 myopathies, even in the severe neonatal form, and suggest that the necklace fibers appear or increase in number over time. (C) 2012 Elsevier B.V. All rights reserved.

Mutations, Clinical Findings and Survival Estimates in South American Patients with X-Linked Adrenoleukodystrophy

In this study, we analyzed the ABCD1 gene in X-linked adrenoleukodystrophy (X-ALD) patients and relatives from 38 unrelated families from South America, as well as phenotypic proportions, survival estimates, and the potential effect of geographical origin in clinical characteristics. Methods: X-ALD patients from Brazil, Argentina and Uruguay were invited to participate in molecular studies to determine their genetic status, characterize the mutations and improve the genetic counseling of their families. All samples were screened by SSCP analysis of PCR fragments, followed by automated DNA sequencing to establish the specific mutation in each family. Age at onset and at death, male phenotypes, genetic status of women, and the effect of family and of latitude of origin were also studied. Results: We identified thirty-six different mutations (twelve novel). This population had an important allelic heterogeneity, as only p. Arg518Gln was repeatedly found (three families). Four cases carried de novo mutations. Intra-familiar phenotype variability was observed in all families. Out of 87 affected males identified, 65% had the cerebral phenotype (CALD). The mean (95% CI) ages at onset and at death of the CALD were 10.9 (9.1-12.7) and 24.7 (19.8-29.6) years. No association was found between phenotypic manifestations and latitude of origin. One index-case was a girl with CALD who carried an ABCD1 mutation, and had completely skewed X inactivation. Conclusions: This study extends the spectrum of mutations in X-ALD, confirms the high rates of de novo mutations and the absence of common mutations, and suggests a possible high frequency of cerebral forms in our population.