Summary Hereditary porphyrias are a group of eight metabolic disorders of the haem biosynthesis pathway that are characterised by acute neurovisceral symptoms, skin lesions, or both. Every porphyria ...is caused by abnormal function of a separate enzymatic step, resulting in a specific accumulation of haem precursors. Seven porphyrias are the result of a partial enzyme deficiency, and a gain of function mechanism has been characterised in a new porphyria. Acute porphyrias present with acute attacks, typically consisting of severe abdominal pain, nausea, constipation, confusion, and seizure, and can be life-threatening. Cutaneous porphyrias present with either acute painful photosensitivity or skin fragility and blisters. Rare recessive porphyrias usually manifest in early childhood with either severe cutaneous photosensitivity and chronic haemolysis or chronic neurological symptoms with or without photosensitivity. Porphyrias are still underdiagnosed, but when they are suspected, and dependent on clinical presentation, simple first-line tests can be used to establish the diagnosis in all symptomatic patients. Diagnosis is essential to enable specific treatments to be started as soon as possible. Screening of families to identify presymptomatic carriers is crucial to decrease risk of overt disease of acute porphyrias through counselling about avoidance of potential precipitants.
Marfan syndrome (MFS) is a connective tissue disorder in which several systems are affected with great phenotypic variability. Although known to be associated with pathogenic variants in the FBN1 ...gene, few genotype–phenotype correlations have been found in proband studies only.
In 1,575 consecutive MFS probands and relatives from the most comprehensive database worldwide, we established survival curves and sought genotype–phenotype correlations.
A risk chart could be established with clinical and genetic data. Premature termination codon variants were not only associated with a shorter life expectancy and a high lifelong risk of aortic event, but also with the highest risk of severe scoliosis and a lower risk for ectopia lentis (EL) surgery. In-frame variants could be subdivided according to their impact on the cysteine content of fibrillin-1 with a global higher severity for cysteine loss variants and the highest frequency of EL surgery for cysteine addition variants.
This study shows that FBN1 genotype–phenotype correlations exist for both aortic and extra-aortic features. It can be used for optimal risk stratification of patients with a great importance for genetic counseling and personalized medicine. This also provides additional data for the overall understanding of the role of fibrillin-1 in various organs.
Iron refractory iron deficiency anemia De Falco, Luigia; Sanchez, Mayka; Silvestri, Laura ...
Haematologica (Roma),
06/2013, Letnik:
98, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Iron refractory iron deficiency anemia is a hereditary recessive anemia due to a defect in the TMPRSS6 gene encoding Matriptase-2. This protein is a transmembrane serine protease that plays an ...essential role in down-regulating hepcidin, the key regulator of iron homeostasis. Hallmarks of this disease are microcytic hypochromic anemia, low transferrin saturation and normal/high serum hepcidin values. The anemia appears in the post-natal period, although in some cases it is only diagnosed in adulthood. The disease is refractory to oral iron treatment but shows a slow response to intravenous iron injections and partial correction of the anemia. To date, 40 different Matriptase-2 mutations have been reported, affecting all the functional domains of the large ectodomain of the protein. In vitro experiments on transfected cells suggest that Matriptase-2 cleaves Hemojuvelin, a major regulator of hepcidin expression and that this function is altered in this genetic form of anemia. In contrast to the low/undetectable hepcidin levels observed in acquired iron deficiency, in patients with Matriptase-2 deficiency, serum hepcidin is inappropriately high for the low iron status and accounts for the absent/delayed response to oral iron treatment. A challenge for the clinicians and pediatricians is the recognition of the disorder among iron deficiency and other microcytic anemias commonly found in pediatric patients. The current treatment of iron refractory iron deficiency anemia is based on parenteral iron administration; in the future, manipulation of the hepcidin pathway with the aim of suppressing it might become an alternative therapeutic approach.
PURPOSE OF REVIEWMany studies over the past decade have together identified new genes including modifier genes and new regulation and pathophysiological mechanisms in inherited inborn diseases of the ...heme biosynthetic pathway. A new porphyria has been characterizedX-linked protoporphyria and the perspective to have innovative treatment at very short-term became a reality. We will summarize how recent data on both ALAS1 and ALAS2 have informed our understanding of disease pathogenesis with an emphasis on how this information may contribute to new therapeutic strategies.
RECENT FINDINGSThe development of clinical and biological porphyria networks improved the long-term follow up of cohorts. The ageing of patients have allowed for the identification of novel recurrently mutated genes, and highlighted long-term complications in acute hepatic porphyrias. The treatment of hepatic porphyrias by an RNAi-targeting hepatic ALAS1 is actually tested and may lead to improve the management of acute attacks.In erythropoietic porphyrias, the key role of ALAS2 as a gate keeper of the heme and subsequently hemoglobin synthesis has been demonstrated. Its implication as a modifier gene in over erythroid disorders has also been documented.
SUMMARYThe knowledge of both the genetic abnormalities and the regulation of heme biosynthesis has increased over the last 5 years and open new avenues in the management of erythropoietic and acute hepatic porphyrias.
Background & Aims
Upregulation of hepatic delta‐aminolevulinic acid synthase 1 with accumulation of potentially toxic heme precursors delta‐aminolevulinic acid and porphobilinogen is fundamental to ...the pathogenesis of acute hepatic porphyria. Aims: evaluate long‐term efficacy and safety of givosiran in acute hepatic porphyria.
Methods
Interim analysis of ongoing ENVISION study (NCT03338816), after all active patients completed their Month 24 visit. Patients with acute hepatic porphyria (≥12 years) with recurrent attacks received givosiran (2.5 mg/kg monthly) (n = 48) or placebo (n = 46) for 6 months (double‐blind period); 93 received givosiran (2.5 mg or 1.25 mg/kg monthly) in the open‐label extension (continuous givosiran, n = 47/48; placebo crossover, n = 46/46). Endpoints included annualized attack rate, urinary delta‐aminolevulinic acid and porphobilinogen levels, hemin use, daily worst pain, quality of life, and adverse events.
Results
Patients receiving continuous givosiran had sustained annualized attack rate reduction (median 1.0 in double‐blind period, 0.0 in open‐label extension); in placebo crossover patients, median annualized attack rate decreased from 10.7 to 1.4. Median annualized days of hemin use were 0.0 (double‐blind period) and 0.0 (open‐label extension) for continuous givosiran patients and reduced from 14.98 to 0.71 for placebo crossover patients. Long‐term givosiran led to sustained lowering of delta‐aminolevulinic acid and porphobilinogen and improvements in daily worst pain and quality of life. Safety findings were consistent with the double‐blind period.
Conclusions
Long‐term givosiran has an acceptable safety profile and significantly benefits acute hepatic porphyria patients with recurrent attacks by reducing attack frequency, hemin use, and severity of daily worst pain while improving quality of life.
Recurrent attacks of acute intermittent porphyria (AIP) result in poor quality of life and significant risks of morbidity and mortality. Liver transplantation (LT) offers a cure, but published data ...on outcomes after LT are limited. We assessed the pretransplant characteristics, complications, and outcomes for patients with AIP who received a transplant. Data were collected retrospectively from the European Liver Transplant Registry and from questionnaires sent to identified transplant and porphyria centers. We studied 38 patients who received transplants in 12 countries from 2002 to 2019. Median age at LT was 37 years (range, 18‐58), and 34 (89%) of the patients were women. A total of 9 patients died during follow‐up, and 2 patients were retransplanted. The 1‐year and 5‐year overall survival rates were 92% and 82%, which are comparable with other metabolic diseases transplanted during the same period. Advanced pretransplant neurological impairment was associated with increased mortality. The 5‐year survival rate was 94% among 19 patients with moderate or no neuropathy at LT and 83% among 10 patients with severe neuropathy (P = 0.04). Pretransplant renal impairment was common. A total of 19 (51%) patients had a GFR < 60 mL/minute. Although few patients improved their renal function after LT, neurological impairments improved, and no worsening of neurological symptoms was recorded. No patient had AIP attacks after LT, except for a patient who received an auxiliary graft. LT is a curative treatment option for patients with recurrent attacks of AIP. Severe neuropathy and impaired renal function are common and increase the risk for poor outcomes. If other treatment options fail, an evaluation for LT should be performed early.
Thoracic aortic aneurysm and dissection (TAAD) is an autosomal-dominant disorder with major life-threatening complications. The disease displays great genetic heterogeneity with some forms allelic to ...Marfan and Loeys-Dietz syndrome, and an important number of cases still remain unexplained at the molecular level. Through whole-exome sequencing of affected members in a large TAAD-affected family, we identified the c.472C>T (p.Arg158∗) nonsense mutation in MFAP5 encoding the extracellular matrix component MAGP-2. This protein interacts with elastin fibers and the microfibrillar network. Mutation screening of 403 additional probands identified an additional missense mutation of MFAP5 (c.62G>T p.Trp21Leu) segregating with the disease in a second family. Functional analyses performed on both affected individual’s cells and in vitro models showed that these two mutations caused pure or partial haploinsufficiency. Thus, alteration of MAGP-2, a component of microfibrils and elastic fibers, appears as an initiating mechanism of inherited TAAD.
Individuals with mosaic pathogenic variants in the FBN1 gene are mainly described in the course of familial screening. In the literature, almost all these mosaic individuals are asymptomatic. In this ...study, we report the experience of our team on more than 5,000 Marfan syndrome (MFS) probands.
Next-generation sequencing (NGS) capture technology allowed us to identify five cases of MFS probands who harbored a mosaic pathogenic variant in the FBN1 gene.
These five sporadic mosaic probands displayed classical features usually seen in Marfan syndrome. Combined with the results of the literature, these rare findings concerned both single-nucleotide variants and copy-number variations.
This underestimated finding should not be overlooked in the molecular diagnosis of MFS patients and warrants an adaptation of the parameters used in bioinformatics analyses. The five present cases of symptomatic MFS probands harboring a mosaic FBN1 pathogenic variant reinforce the fact that apparently asymptomatic mosaic parents should have a complete clinical examination and a regular cardiovascular follow-up. We advise that individuals with a typical MFS for whom no single-nucleotide pathogenic variant or exon deletion/duplication was identified should be tested by NGS capture panel with an adapted variant calling analysis.
Marfan syndrome (MFS) is a rare autosomal dominant connective tissue disorder related to variants in the FBN1 gene. Prognosis is related to aortic risk of dissection following aneurysm. MFS clinical ...variability is notable, for age of onset as well as severity and number of clinical manifestations. To identify genetic modifiers, we combined genome-wide approaches in 1070 clinically well-characterized FBN1 disease-causing variant carriers: (1) an FBN1 eQTL analysis in 80 fibroblasts of FBN1 stop variant carriers, (2) a linkage analysis, (3) a kinship matrix association study in 14 clinically concordant and discordant sib-pairs, (4) a genome-wide association study and (5) a whole exome sequencing in 98 extreme phenotype samples.Three genetic mechanisms of variability were found. A new genotype/phenotype correlation with an excess of loss-of-cysteine variants (P = 0.004) in severely affected subjects. A second pathogenic event in another thoracic aortic aneurysm gene or the COL4A1 gene (known to be involved in cerebral aneurysm) was found in nine individuals. A polygenic model involving at least nine modifier loci (named gMod-M1-9) was observed through cross-mapping of results. Notably, gMod-M2 which co-localizes with PRKG1, in which activating variants have already been described in thoracic aortic aneurysm, and gMod-M3 co-localized with a metalloprotease (proteins of extra-cellular matrix regulation) cluster. Our results represent a major advance in understanding the complex genetic architecture of MFS and provide the first steps toward prediction of clinical evolution.
Heritable thoracic aortic aneurysms and dissections (hTAAD) are life-threatening complications of well-known syndromic diseases or underdiagnosed nonsyndromic heritable forms (nshTAAD). Both have an ...autosomal dominant transmission and are genetically heterogeneous. Our objective was to describe the relevance of molecular diagnosis in these patients and the contribution of each gene in nshTAAD.
Two hundred twenty-six consecutive nshTAAD probands, either young (<45 years) sporadic or familial cases were included. A next-generation sequencing capture panel comprising 23 known disease-causing genes was performed.
Class 4 or 5 variants were identified in 18% of the nshTAAD probands, while class 3 variants were found in 10% of them. The yield in familial cases was greater than in sporadic cases. SMAD3 and FBN1 genes were the major disease-causing genes. Unexpectedly, no premature termination codon variant was identified in the FBN1 gene. Furthermore, we report for the first time that aortic dissection or surgery occurred significantly more often and earlier in probands with a class 4 or 5 pathogenic variant.
This study indicates that genetic screening using NGS is efficient in young and familial nshTAAD. The presence of a pathogenic variant has a possible predictive value, which needs to be further investigated because it may influence care.
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