Bruno Drera

Loeys-Dietz syndrome type I and type II: clinical findings and novel mutations in two Italian patients

BackgroundLoeys-Dietz syndrome (LDS) is a rare autosomal dominant disorder showing the involvement of cutaneous, cardiovascular, craniofacial, and skeletal systems. In particular, LDS patients show arterial tortuosity with widespread vascular aneurysm and dissection, and have a high risk of aortic dissection or rupture at an early age and at aortic diameters that ordinarily are not predictive of these events. Recently, LDS has been subdivided in LDS type I (LDSI) and type II (LDSII) on the basis of the presence or the absence of cranio-facial involvement, respectively. Furthermore, LDSII patients display at least two of the major signs of vascular Ehlers-Danlos syndrome. LDS is caused by mutations in the transforming growth factor (TGF) beta-receptor I (TGFBR1) and II (TGFBR2) genes. The aim of this study was the clinical and molecular characterization of two LDS patients.MethodsThe exons and intronic flanking regions of TGFBR1 and TGFBR2 genes were amplified and sequence analysis was performed.ResultsPatient 1 was a boy showing dysmorphic signs, blue sclerae, high-arched palate, bifid uvula; skeletal system involvement, joint hypermobility, velvety and translucent skin, aortic root dilatation, tortuosity and elongation of the carotid arteries. These signs are consistent with an LDSI phenotype. The sequencing analysis disclosed the novel TGFBR1 p.Asp351Gly de novo mutation falling in the kinase domain of the receptor. Patient 2 was an adult woman showing ascending aorta aneurysm, with vascular complications following surgery intervention. Velvety and translucent skin, venous varicosities and wrist dislocation were present. These signs are consistent with an LDSII phenotype. In this patient and in her daughter, TGFBR2 genotyping disclosed in the kinase domain of the protein the novel p.Ile510Ser missense mutation.ConclusionWe report two novel mutations in the TGFBR1 and TGFBR2 genes in two patients affected with LDS and showing marked phenotypic variability. Due to the difficulties in the clinical approach to a TGFBR-related disease, among patients with vascular involvement, with or without aortic root dilatation and LDS cardinal features, genotyping is mandatory to clarify the diagnosis, and to assess the management, prognosis, and counselling issues.

Two novel SLC2A10/GLUT10 mutations in a patient with arterial tortuosity syndrome†

Bruno Drera, Andrea Guala, Nicoletta Zoppi, Rita Gardella, Piergiorgio Franceschini, Sergio Barlati, and Marina Colombi* Division of Biology and Genetics, Department of Biomedical Sciences and Biotechnology, University of Brescia, Brescia, Italy Ambulatorio di Genetica Clinica, Ospedale SS. Pietro e Paolo, Borgosesia, Italy Dipartimento di Scienze Pediatriche e dell’Adolescenza, Servizio di Genetica Clinica, Università degli Studi di Torino, Torino, Italy

Arterial tortuosity syndrome in two Italian paediatric patients

BackgroundArterial tortuosity syndrome (ATS) (OMIM #208050) is a rare autosomal recessive connective tissue disorder characterized by tortuosity and elongation of the large and medium-sized arteries, propensity to aneurysms formation, vascular dissection, and pulmonary arteries stenosis. ATS is caused by mutations in SLC2A10 gene, encoding for the facilitative glucose transporter 10 (GLUT10). So far, 17 SLC2A10 mutations have been reported in 32 families, two of which were Italian with a total of five patients. Here we present the clinical and molecular characterization of two novel Italian paediatric ATS patients.MethodsThe exons and intronic flanking regions of SLC2A10 gene were amplified and direct sequencing was performed.ResultsIn both patients, the involvement of major- and medium-sized arteries was characteristic; the nonvascular connective tissue manifestations were mild and not pathognomic of the disorder. Both patients, born from non-consanguineous parents, were heterozygous for two different SLC2A10 mutations, three of which were recurrent and one was novel (p.Arg231Trp). This mutation is localized at the endofacial loop between the transmembrane domains 6 and 7 of GLUT10.ConclusionTwo novel ATS patients were characterized at clinical and molecular level. Overall, four ATS unrelated families are known in Italy so far. Though ATS clinical delineation improved in the last years, further works in the comprehension of disease presentation and complications onset, particularly in paediatric age, and on ATS molecular basis are needed to add new insights for diagnosis and prevention strategies for related complications.

Mutations in TGFBR2 gene cause spontaneous cervical artery dissection

Mutations in the genes encoding transforming growth factor β receptors 1 and 2 (TGFBR1 and TGFBR2) have recently been associated with hereditary connective tissue disorders with widespread vascular involvement, including arterial dissection. To determine whether mutations in these genes cause spontaneous cervical artery dissection (sCAD), all coding exons of TGFBR1 and TGFBR2 were sequenced in 56 consecutive patients with sCAD. Novel TGFBR2 disease causing mutations were found in two patients. The two mutations were the pK327R substitution affecting the kinase domain of TGFBR2 and the pC138R substitution falling in the extracellular domain of the protein, involved in TGFβ binding and signalling. No TGFBR1 mutation was found. The findings indicate that TGFBR2 gene mutations are responsible for sCAD in 3.6% (95% CI 0.0 to 8.4) of cases, have implications in understanding the role of TGFβ signalling in the pathogenesis of sCAD and emphasise the importance of considering molecular characterisation of the TGFBR2 gene in these patients, regardless of the presence of clinical features suggestive of hereditary connective tissue disorders.

Identification of a novel TGFBR1 mutation in a Loeys–Dietz syndrome type II patient with vascular Ehlers–Danlos syndrome phenotype

To the Editor: Loeys–Dietz syndrome (LDS) is a rare connective tissue disorder with autosomal dominant inheritance and characterized by hypertelorism, bifid uvula and/or cleft palate, arterial tortuosity with widespread vascular aneurysm and dissection. LDS shows the involvement of cutaneous, skeletal and cardiovascular systems and a wide range of intraand inter-familiar variability (1, 2). Recently, LDS has been distinguished in LDS type I (LDSI) and type II (LDSII), on the basis of the presence or the absence of craniofacial involvement (2). Furthermore, LDSII patients display at least two of the characteristic signs of Ehlers–Danlos syndrome (EDS) vascular type (2). Vascular EDS diagnosis is made on the basis of major (characteristic facial dysmorphisms, easy bruising, thin or translucent skin, and arterial/ uterine/intestinal fragility or rupture) and minor diagnostic criteria (3). LDS is as a result of mutations in transforming growth factor (TGF)-beta receptor I (TGFBR1) and II (TGFBR2) genes (2), whereas vascular EDS results from mutations in COL3A1 gene, encoding for type III procollagen (COLLIII) (3). TGFBR1, a type I receptor for the different members of the TGFb superfamily, is a transmembrane serine/threonine kinase, composed of a small cysteine-rich extracellular domain, a single transmembrane region, and a cytoplasmic juxtamembrane region, including a conserved glycine-serine-rich (GS) domain (176–205 residues) adjacent to the amino-terminal boundary of the kinase domain (206–496 residues) (4). TGFbs bind to a TGFBR2 homodimer, which recruits a TGFBR1 homodimer and activates it by phosphorylation of serine and threonine residues in the GS region, resulting in propagation of downstream signalling (5). Thus far, 19 TGFBR1 disease-causing mutations have been reported; all are missense mutations falling in the kinase domain or in the GS region of the receptor (2, 6). In particular, four of these mutations were detected in LDSII patients. In the 12 LDSII so far reported eight TGFBR2 mutations were also disclosed (2). In this work, we report a new Italian patient affected with LDSII and carrying a novel TGFBR1 mutation. The proband (II.2), a 45-year-old man born from non-consanguineous parents (Fig. 1a), showed facies with a prominent and narrow nose, thin lips and paucity of subcutaneous adipose tissue, absence of hypertelorism, bifid uvula and cleft palate, small joints hypermobility (Beighton score 2/10), paste and soft skin with mild hyperextensibility, atrophic scars on knees, dissection of both internal iliac arteries and right femoral artery, occurred at 40 and 44, respectively (Fig. 1b). Echocardiogram displayed no aortic root dilatation with values at normal upper limit (annulus 25 mm, sinuses of Valsalva 35 mm and sinotubular junction 27 mm), ascending aorta 39 mm, mild mitral valve prolapse, and no great vessels tortuosity. Computerized axial tomography of head and neck did not show tortuosity and/or aneurysms of arteries. The 85-year-old father (I.1), the 40-year-old brother (II.3) and the 16-year-old daughter (III.1) of the proband (Fig. 1a) were in good health and did not display facial, cutaneous, and articular signs. The patient’s mother (I.2) died for a not diseaserelated accident at the age of 45, and we could not evaluate her phenotype. As the proband’s phenotype was evocative of vascular EDS, the search for mutations in the COL3A1 gene was performed using reverse transcription and polymerase chain reaction

De novo occurrence of the 730insG recurrent mutation in an Italian family with the ichthyotic variant of Vohwinkel syndrome, loricrin keratoderma

To the Editor: Palmoplantar keratodermas (PPK) are a group of genodermatosis showing clinical and genetic heterogeneity and characterized by marked thickening of the epidermis on the palms and soles (1). Recently, the term loricrin keratoderma (LK) has been suggested to group dominantly inherited PPK with different clinical presentation, that is non-bullous congenital ichthyosiform erythroderma, progressive symmetric erythrokeratoderma, and the variant with ichthyosis of Vohwinkel syndrome (VS), carrying mutations in loricrin gene (LOR) (2–6). In all LK patients, the common signs are the palmoplantar honeycomb hyperkeratosis and ichthyosis (6, 7). Collodion baby was sometimes reported, independently from the clinical evolution of the patients (5–7). The originally described VS, because of mutations in connexin 26 gene, shows: palmoplantar honeycomb hyperkeratosis; constricting fibrous bands encircling fingers or toes, that is pseudoainhum, leading to autoamputation of the fifth finger because of circulatory impairment; starfish-shaped hyperkeratotic lesions on extensor surfaces; and high-tone deafness (2, 3, 6, 8). By contrast, in the loricrin variant of VS, the hearing impairment and starfish-shaped hyperkeratosis are absent and a generalized non-erythrodermic ichthyosis is described (2, 6). LOR, mapping to the locus 1q21, has a simple genomic structure with a single intron and the coding region spanning a single exon, and contains GC-rich nucleotide regions encoding glycine-rich sequences (3, 9, 10). Loricrin, a small glycine-serine-cysteine-rich basic protein, is synthesized in the granular layer of the epidermis. The protein, deposited beneath the plasma membrane, and cross-linking to several cytosolic proteins, forms the cornified envelope (CE) of the keratinocytes in the late stage of differentiation (3, 11). The CE, acting as a scaffold for the deposition of the extracellular lamellar bilayers, is essential for the formation of a normally keratinized epidermis (3). To date, only three different LOR mutations, i.e. 730insG, 662insT and 709insC, have been reported in eight LK families (6, 7). In particular, the 730insG mutation was found in six families with different clinical presentation: two from Japan, three from UK, and one from Germany (3, 5, 7, 12–14). In this genodermatosis, the genotype–phenotype correlation is difficult to envisage also for the limited number of patients. Here, we report the first Italian family affected with the VS ichthyotic variant of LK, and its molecular characterization. The proband (II:2), a 23-years-old woman born from non-consanguineous healthy parents [Fig. 1(a)], displayed: palmar and plantar reddish honeycomb hyperkeratosis extending onto flexural surface of the wrists [Fig. 1(b), i]; increased skin markings on the knuckles; constricting bands affecting proximal and distal interfalangeal joints of all fingers [Fig. 1(b), ii]; diffuse ichthyosiform dermatosis with fine, white scales. The patient underwent to several surgical treatments for pseudoainhum of both fifth fingers. The 2-years-old daughter showed palmar and plantar honeycomb hyperkeratosis [Fig. 1(c), i]; no constricting bands of the fingers, thought skin marking on the dorsal surface of the fingers was increased [Fig. 1(c), ii]; slightly visible xerotic skin. In both affected family members the nails, eyes, hairs and teeth were normal, and the audiogram gave no evidence of hearing impairment. Previously, the phenotype was reported to be fully penetrant even at 18 months and to show variation in severity even in the same family (3). In our

Clinical, neuroradiological and molecular features of a patient affected by pseudoxhantoma elasticum associated to carotid rete mirabile: Case report

Clinica Neurologica, Dipartimento di Scienze Mediche e Chirurgiche, Universita degli Studi di Brescia, Brescia, Italy Sezione di Biologia e Genetica, Dipartimento di Scienze Biomediche e Biotecnologie, Universita degli Studi di Brescia, Brescia, Italy Neurologia Vascolare, Stroke Unit, Spedali Civili di Brescia, Brescia, Italy Neuroradiologia, Dipartimento di Diagnostica per Immagini, Universita degli Studi di Brescia, Brescia, Italy

Recurrence of the p.R156X TNNI2 mutation in distal arthrogryposis type 2B

To the Editor: Distal arthrogryposes (DAs) are a group of rare genetic disorders, with autosomal dominant inheritance, characterized by congenital contractures of two or more different body areas with a consistent pattern of distal involvement without primary neurological disease (1, 2). DAs classification includes 10 different types, showing distal contractures and specific additional features (1, 2). Among these, DA type 2B (DA2B; OMIM 601680) is characterized by congenital contractures of hands/wrists and feet, facial features, including downslanting palpebral fissures and prominent nasolabial folds, and normal intelligence (2). Mutations causing DA2B have been reported in three genes encoding proteins constituting the contractile complex of skeletal muscle fibers: TNNI2 (fast-twitch skeletal troponin I isoform), TNNT3 (fast-twitch skeletal troponin T isoform), and MYH3 (embryonic myosin heavy chain) (3–6). Mutations in these genes account for about half of DA2B cases (6). In particular, in TNNI2, three different mutations, accounting for about 10% of DA2B studied families, have been reported: the p.R174Q, in two families; the p.R156X, in two families (3); and the p.DE167, in one family (4). In spite of this locus heterogeneity, all patients with DA2B show common clinical signs with low intrafamiliar variability; furthermore, MYH3 mutations cause either DA2B or the clinically different DA2A (6). TNNI2 belongs to a multigene family whose members encode three different troponin I isoforms, expressed in a temporaland musclespecific manner (7–9). Troponin I, together with troponin C and troponin T, constitutes the troponin complex of the striated muscle thin filament, which binds tropomyosin and regulates myosin–actin interaction. Troponin I, which binds actin, inhibits, at low Ca concentration, muscle contraction (10). The role of mutated troponin I in the alteration of myogenesis, leading to the DA2B phenotype, is supported by Drosophila troponin I hortologue mutants showing abnormalities of wings and limb skeletal muscles (11). We report the first Italian DA2B family characterized at the molecular level. The propositus was a male born of non-consanguineous parents (Fig. 1a) at 35 weeks by elective cesarean section. Upon delivery, he required mechanical ventilatory support. Neurologically, he was hypotonic with asymmetric posture and poor reactivity. He showed downslanted palpebral fissures, inner epichantal folds, low nasal bridge, low set ears, cleft palate and micrognathia; fracture of the right femur, bilateral inguinal hernia and undescended testes; bilateral and symmetric hand contractures characterized by clenched fists, overlapping fingers at birth, ulnar deviation, camptodactyly and cutaneous syndactyly of the left 4th and 5th fingers (Fig. 1b, i); bilateral and symmetric clubfoot anomaly and overlapping toes; and prominent right scapula. Bilateral clubfoot and malformations of the hands were surgically treated (Fig. 1b, iii). At the age of 23 years, he showed triangular-shaped face with frontal bossing, prominent nasolabial folds, and broad and long nasal bridge (Fig. 1b, ii); proximal joints stiffness; hypotrophic muscles; scoliosis; normal electromyography and articular pain, due to early developed arthrosis. The facial features, the hands (Fig. 1c) and the feet of the mother showed a similar phenotype; precocious and severe proximal and distal joints arthrosis, spondylolisthesis and multiple herniated disks were also present. The mother did not show scoliosis and cleft palate, rare traits observed in DA2B (2). The propositus showed DA2B occasional features, such as cryptorchidism and inguinal hernia (2, 3). Cleft palate is reported in DA2A (Freeman-Sheldon syndrome; OMIM 193700) (1, 2) and is a key feature of DA3 (Gordon syndrome; OMIM 114300) in addition to camptodactyly and clubfoot (12). In our family, and in the DA3 families described, the cleft palate is a sign showing intrafamilial variability (12). Cleft palate is a rare trait that should be considered as an