M. De Marchi

Unbiased next generation sequencing analysis confirms the existence of autosomal dominant Alport syndrome in a relevant fraction of cases

The mode of inheritance of Alport syndrome (ATS) has long been controversial. In 1927, the disease was hypothesized as a dominant condition in which males were more severely affected than females. In 1990, it was considered an X‐linked (XL) semidominant condition, due to COL4A5 mutations. Later on, a rare autosomal recessive (AR) form due to COL4A3/COL4A4 mutations was identified. An autosomal dominant (AD) form was testified more recently by the description of some large pedigrees but the real existence of this form is still questioned by many and its exact prevalence is unknown. The introduction of next generation sequencing (NGS) allowed us to perform an unbiased simultaneous COL4A3‐COL4A4‐COL4A5 analysis in 87 Italian families (273 individuals) with clinical suspicion of ATS. In 48 of them (55%), a mutation in one of the three genes was identified: the inheritance was XL semidominant in 65%, recessive in 4% and most interestingly AD in 31% (15 families). The AD form must therefore be seriously taken into account in all pedigrees with affected individuals in each generation. Furthermore, a high frequency of mutations (>50%) was shown in patients with only 1 or 2 clinical criteria, suggesting NGS as first‐level analysis in cases with a clinical suspicion of ATS.

Analysis of the CARD15 variants R702W, G908R and L1007fs in Italian IBD patients

CARD15 on chromosome 16 is the only IBD susceptibility gene identified among several mapped loci. Its recurrent variants R702W, G908R and L1007fs have shown significant association with Crohns disease (CD), but not with ulcerative colitis (UC), in different Caucasian populations. We analysed these three variants in 184 CD and 92 UC Italian patients and in 177 healthy controls. L1007fs and G908R were independently associated with CD, while R702W showed a nonsignificant increase. After combining the three variants together, 32.6% of CD patients were positive vs 18.6% of the controls. The association was stronger for homozygotes and compound heterozygotes, OR 13.9 (1.8–108), and weaker but still significant for simple heterozygotes, OR 1.7 (1.0–2.9). An excess of homozygotes/compound heterozygotes also resulted from the comparison with Hardy–Weinberg expectations. Phenotype–genotype correlations were analysed first by univariate logistic regression and then by multivariate analysis, the effect of CARD15 positivity being adjusted according to the status of smoking, familiarity and sex, so as to focus on the predictivity of genetic and environmental risk factors on the clinical phenotype. Significant risk estimates of the CARD15 genotype were obtained for stricturing vs inflammatory behaviour, OR 2.76 (1.2–6.3), and for penetrating behaviour, 2.59 (1.0–6.6), and marginally significant for ileal vs colic location, OR 3.0 (0.9–9.8). Our findings indicate that the association of the CARD15 genotype with behaviour and location of disease holds also for the Italian population.

Definition of the smallest pathological CAG expansion in SCA7.

To the Editor: Spinocerebellar ataxia 7 (SCA7), one of the known diseases caused by the expansion of a coding region CAG repeat [reviewed in (1, 2)], is a neurodegenerative disorder affecting the cerebellum, brainstem and retina. It is characterised by the phenotype of autosomal dominant cerebellar ataxia (ADCA) associated with macular degeneration (type II phenotype) (3). The SCA7 gene encodes a nuclear 892 amino acid protein of unknown function, whose N-terminal segment contains a polyglutamine stretch believed to exert a toxic effect when expanded. Normal SCA7 alleles range from six to 17 CAG repeats; the ten-repeat allele is the most common, with a frequency of 71.5% (4). Pathological alleles from 37 to 130 CAGs (5), from 40 to 200 CAGs (6) and from 38 to 103 CAGs (4) have been reported. Alleles bearing 28–35 repeats can give rise, during paternal transmission, to disease alleles, but do not seem to be associated with SCA7 phenotype (7). However, the lower boundary of the pathological range is still controversial. We have analysed SCA7 CAG repeat number in 2 patients and 11 relatives of an Italian ADCA type II family (Man family; Table 1). Polymerase chain reaction (PCR) products obtained from genomic DNA amplified using primers 4U1024 5%-HEX-labelled and 4U716 (8) were separated on an ABI Prism 377 automated DNA sequencer and analysed with the Genescan 2.0 software (Perkin Elmer, Monza, Italy). CAG expansions of the SCA7 gene were first found in patient II-2 (10/36 repeats) and his son III-1 (8/42). Unsteadiness in the gait arose at 63 years of age in the father and at 23 years of age in the son, followed by decreased visual acuity after 2 and 6 years, respectively. Both patients presented with cerebellar ataxia and dysarthria in association with pyramidal signs, hyper-reflexia of the lower limbs and Babinski’s sign. When examined at 30 years of age, the son also showed a decrease in saccadic velocity, supranuclear ophthalmoparesis, hypo-acusia, decreased vibratory sensitivity and dystonic movements in the distal limbs. Optic atrophy without maculopathy and a marked Tritan axis defect on D-15 dichromatous Farnsworth test were found in both patients. Molecular analysis of other relatives demonstrated a 34 CAG allele in II-3 (65 years of age) and in III-3, one of her sons (41 years of age) (Fig. 1). II-3 presented unsteadiness of the gait, especially when running, generalised hyper-reflexia, except for hypo-reflexia of the ankles, extensor plantar reflex and decreased vibratory sensitivity of the lower limbs. Visual acuity was also decreased and angiofluorography demonstrated initial signs of pigmentary macular dystrophy. Magnetic resonance of the cerebellum failed to demonstrate any sign of atrophy. The son carrying the 34 CAG allele was asymptomatic. All SCA genes show a limited polymorphism of normal alleles and a wide range of pathological unstable CAG expansions. Symptomatic SCA7 individuals show a number of CAG repeats \37. Gouw et al. (4) described an asymptomatic individual, 48 years of age, who carried a

Gonadal agenesis in a phenotypically normal female with positive H-Y antigen

SummaryIn a girl with primary amenorrhea, born from a consanguineous marriage, bilateral absence of gonads was established histologically. Cytogenetic studies demonstrated a 46,XY karyotype, and H-Y antigen determination was positive. In contrast with most reported cases of XY females with gonadal agenesis, normal development of female internal and external genitalia was present. Clinical and endocrinological features are reported, and the possible basis for the malformation is discussed.

Central core disease: Histochemical and ultrastructural study of muscle biopsies of father and daughter

SummaryTwo cases of central core disease, father and daughter, of a family with dominant autosomal inheritance, are presented, one with bilateral congenital dislocation of the hip. Muscle biopsy was performed in both cases. Oxidative enzymes evidenced only type I fibers, most of them presenting a central core and not uncommonly more than one. On electron microscopy the cores generally appeared well demarcated from the surrounding fibrils and were characterized by lack of mitochondria and abnormalities of the Z line. Transitional aspects from normal fibers to completely unstructured cores were observed, as well as from well structured and unstructured cores. These findings are discussed in the light of the previous literature and particular attention is paid to the problem of differentiation between central core and multicore disease. The pathogenesis of the muscular alteration is also discussed in relation with the possibility of their neurogenic origin. Eventually, the histochemical and ultrastructural similarities between central cores and target fibers are focused.ZusammenfassungAus einer Familie, in welcher die Erkrankung autosomal dominant vererbt wird, werden Vater und Tochter mit Central Core Disease beschrieben. Bei einem Fall besteht außerdem eine bilaterale congenitale Hüftgelenksluxation. Die in beiden Fällen durchgeführte Muskelbiopsie ergab folgendes: Dargestellt durch den histochemischen Nachweis oxydativer Enzyme fanden sich ausschließlich Typ-I-Fasern, von welchen die meisten ein und nicht selten sogar mehrere „Central Core“ aufwiesen. In der Elektronenmikroskopie erschienen die „Cores“ allgemein gut von den umgebenden Fibrillen abgegrenzt und waren durch das Fehlen von Mitochondrien und Anomalien der Z-Linien charakterisiert. Es wurden Übergänge zwischen normalen Fasern einerseits und vollständig unstrukturierten „Cores“ andererseits beobachtet, wie auch Übergänge von gut strukturierten und unstrukturierten „Cores“. Die Befunde werden unter Berücksichtigung der einschlägigen Literatur diskutiert. Es wird besonders eingegangen auf das Problem der Unterscheidung zwischen „Central Core“ und „Multiple Core“ und „Multiple Core Disease“. Die Pathogenese der Muskelveränderung wird im besondern auch im Hinblick auf die mögliche neurogene Verursachung diskutiert. Es wird im weitern auf die histochemischen und ultrastrukturellen Gemeinsamkeiten zwischen „Central Cores“ und „Target Fibers“ eingegangen.

True hermaphroditism with XX/XY sex chromosome mosaicism: Report of a case

A case of true hermaphroditism with 46, XX/46, XY karyotype is reported. The propositus, reared as a male, showed ambiguous external genitalia with perineoscrotal hypospadias, and internal genitalia represented by bilateral ovotestes, normal uterus and tubes. Periodic menstrual bleedings appeared at puberty. The endocrinologic data demonstrated the secretory activity of both the ovarian and the testicular tissue. The analysis of red cell, lymphocyte and serum markers, done on the propositus and on his parents, failed to show any evidence of double fertilization. On this basis, the origin of the XX/XY condition (mosaicism versus chimerism) and its developmental consequences are discussed.

Primary hyperoxaluria: report of an Italian family with clear sex conditioned penetrance

We report the clinical and genetic study of a primary hyperoxaluria type I (PH1) family with two sisters homozygous for p.Gly170Arg who are still asymptomatic at age 29 and 35, and two brothers, also homozygous for the same mutation, who are affected since age 27 and 30. The clear sex difference observed in this family and in others reported in the literature fits well with the prevalence of males over females in the Italian registry. In the KO model of PH1, only male mice develop renal stones, suggesting that the sex difference may affect both oxalate production and stone formation. A likely mechanism is the sex-related expression of glycolate oxidase shown in experimental animals. The stable isotope method recently developed by Huidekoper and van Woerden for in vivo assessment of the endogenous oxalate production could help to clarify the issue in humans.

Copy number variants analysis in a cohort of isolated and syndromic developmental delay/intellectual disability reveals novel genomic disorders, position effects and candidate disease genes.

Array‐comparative genomic hybridization (array‐CGH) is a widely used technique to detect copy number variants (CNVs) associated with developmental delay/intellectual disability (DD/ID).

Alport syndrome with type I membranoproliferative glomerulonephritis.

Alport Syndrome with Type I Membranoproliferative Glomerulonephritis M. Meroni A. Sessa G. Battini L.T. Torri Tarelli T. Bertani A. Renieri M. Seri M. De Marchi UO Nefrologia e Dialisi, Vimercate, Istituto di Anatomia Umana Normale, Università degli Studi, Milano, Divisione di Nefrologia, Ospedali Riuniti, Bergamo, Cattedra di Genetica Medica, Dipartimento di Biologia Molecolare, Università di Siena, Dipartimento di Scienze Cliniche e Biologiche, Università di Torino, Ospedale San Luigi Gonzaga, Orbassano, Italia

Familial progressive external ophthalmoplegia with multisystem abnormalities: “new” features raising nosological problems

SummaryA 32-year-old female presented with progressive external ophthalmoplegia (PEO) and multisystem abnormalities, strikingly associated with myotonia and muscle hypertrophy. These two features were not found in her brother, who had a complex neuromuscular disorder complicating chronic PEO. In both subjects muscle biopsy revealed “ragged-red” fibres and myofibres containing glycogen granules, which were never bound by membranes. A severe demyelinating neuropathy was revealed by electrophysiological and morphological studies. Cranial CT scan showed extensive demyelination of the cerebral white matter. Genetic studies demonstrated that this familial syndrome is transmitted as an autosomal recessive trait.