Martino Ruggieri

The clinical and diagnostic implications mosaicism in the neurofibromatoses

Neurofibromatosis type 1 and type 2 both occur in mosaic forms. Mosaicism results from somatic mutations. Early somatic mutations cause generalized disease, clinically indistinguishable from nonmosaic forms. Later somatic mutation gives rise to localized disease often described as segmental. In individuals with mosaic or localized manifestations of neurofibromatosis type 1 (segmental neurofibromatosis type 1), disease features are limited to the affected area, which varies from a narrow strip to one quadrant and occasionally to one half of the body. Distribution is usually unilateral but can be bilateral, either in a symmetric or asymmetrical arrangement. Patients with localized neurofibromatosis type 2 have disease-related tumors localized to one part of the nervous system; for example a unilateral vestibular schwannoma with ipsilateral meningiomas or multiple schwannomas in one part of the peripheral nervous system. The recognition of mosaic phenotypes is important. Individuals with the mosaic form, even with a generalized phenotype, are less likely to have severe disease. They also have lower offspring recurrence risk than individuals with the nonmosaic form. The mosaic forms of neurofibromatosis provide a good example of the effects of somatic mutation. It is increasingly recognized that mild and unusual forms of many dominantly inherited disorders are caused by the same mechanism.

Clinical features and viral serologies in children with multiple sclerosis: a multinational observational study

BACKGROUND The full spectrum of clinical manifestations and outcome, and the potential importance of regional or demographic features or viral triggers in paediatric multiple sclerosis (MS), has yet to be fully characterised. Our aim was to determine some of these characteristics in children with MS. METHODS 137 children with MS and 96 control participants matched by age and geographical region were recruited in a multinational study. They underwent structured clinical-demographic interviews, review of academic performance, physical examination, disability assessment (MS patients only), and standardised assays for IgG antibodies directed against Epstein-Barr virus, cytomegalovirus, parvovirus B19, varicella zoster virus, and herpes simplex virus. FINDINGS MS was relapsing-remitting at diagnosis in 136 (99%) children. The first MS attack resembled acute disseminated encephalomyelitis (ADEM) in 22 (16%) of the children, most under 10 years old (mean age 7.4 [SD 4.2] years). Children with ADEM-like presentations were significantly younger than were children with polyfocal (11.2 [4.5] years; p<0.0001) or monofocal (12.0 [3.8] years; p=0.0005) presentations. Permanent physical disability (EDSS>or=4.0) developed within 5 years in 15 (13%) of the 120 children for whom EDSS score was available. 23 (17%) had impaired academic performance, which was associated with increasing disease duration (p=0.02). Over 108 (86%) of the children with MS, irrespective of geographical residence, were seropositive for remote EBV infection, compared with only 61 (64%) of matched controls (p=0.025, adjusted for multiple comparisons). Children with MS did not differ from controls in seroprevalence of the other childhood viruses studied, nor with respect to month of birth, sibling number, sibling rank, or exposure to young siblings. INTERPRETATION Paediatric MS is a relapsing-remitting disease, with presenting features that vary by age at onset. MS in children might be associated with exposure to EBV, suggesting a possible role for EBV in MS pathobiology.

MULTIPLE SCLEROSIS IN CHILDREN UNDER 6 YEARS OF AGE

Objectives: To characterize MS patients with the earliest onset of disease. Background: MS—primarily a disease of young adulthood—begins in childhood in 3 to 5% of cases. However, onset before 10 years of age is considered exceptional. Accordingly, inclusion age at onset is generally between 10 and 59 years. Methods: Information was obtained on patients with MS treated at our institution (n = 6) or from reports in Medline or bibliographies. Onset of disease was before 6 years of age, for a total of 49 patients (29 girls, 20 boys). Results: All patients had clinically defined MS according to Poser’s criteria; 22 were also laboratory supported. The female/male ratio (1.4) was lower than that usually recorded for adult onset MS (2.0) and that of MS with onset between 6 and 15 years (2.2 to 3.0). The group of patients (n = 5) with onset before 24 months of age showed the lowest ratio (0.6) and carried the most unfavorable prognosis. Among initial symptoms, ataxia was preponderant (61%). Optic nerve involvement became more frequent with age. Generalized or partial seizures occurred in 22% of cases. First inter-attack interval was less than 1 year in 63% of the cases. The yearly relapse rate ranged from 1.1 at disease onset to 0.2 after 9 years from disease onset. At follow-up (mean length 6.8 years), the disease was relapsing-remitting in 84% patients and the grade of recovery was complete in 64%. Conclusions: Definite MS can be consistently diagnosed by current criteria for adult onset MS in patients with the earliest onset of disease who show peculiar clinical features and natural history. These findings may suggest a reconsideration of current lower limits for MS diagnostic criteria.

Gross deletions of the neurofibromatosis type 1 (NF1) gene are predominantly of maternal origin and commonly associated with a learning disability, dysmorphic features and developmental delay

Mutation screening in neurofibromatosis type 1 (NF1) families has long been hampered by the complexity of the NF1 gene. By using a novel multi-track screening strategy, 67 NF1 families (54 two-generation, 13 three-generation) with a de novo mutation in the germline of the first generation were studied with two extragenic and 11 intragenic markers. The pathological lesion was identified in 31 cases. Loss of heterozygosity (LOH) in the affected individual revealed a gross gene deletion in 15 of the two-generation families; in 12 (80%) of them, the deletion was maternally derived. Eleven patients with a gross deletion exhibited developmental delay, ten had dysmorphic features and six manifested a learning disability. No gross deletion was apparent in any of the 13 three-generation families, suggesting that such lesions are subject to more intense selection. In these families, the new mutation was of paternal origin in 11 kindreds and the underlying mutational event could be characterised in three of them.

Apparent preferential loss of heterozygosity at TSC2 over TSC1 chromosomal region in tuberous sclerosis hamartomas

To investigate the molecular mechanisms of tuberous sclerosis (TSC) histopathologic lesions, we have tested for loss of heterozygosity the two TSC loci (TSC1 and TSC2) and seven tumor suppressor gene‐containing regions (TP53, NF1, NF2, BRCA1, APC, VHL, and MLM) in 20 hamartomas from 18 TSC patients. Overall, eight angiomyolipomas, eight giant cell astrocytomas, one cortical tuber, and three rhabdomyomas were analyzed. Loss of heterozygosity at either TSC locus was found in a large fraction of the informative patients, both sporadic (7/14) and familial (1/4). Interestingly, a statistically significant preponderance of loss of heterozygosity at TSC2 was observed in the sporadic group (P < 0.01). Among the possible explanations considered, the bias in the selection for TSC patients with the most severe organ impairment seems particularly appealing. According to this view, a TSC2 defect might confer a greater risk for early kidney failure or, possibly, a more rapid growth of a giant cell astrocytoma. None of the seven antioncogenes tested showed loss of heterozygosity, indicating that the loss of either TSC gene product may be sufficient to promote hamartomatous cell growth. Finally, the observation of loss of heterozygosity at different markers in an astrocytoma and in an angiomyolipoma from the same patient might suggest the multifocal origin of the second‐hit mutation. Genes Chromosom Cancer 15:18–25 (1996).

The different forms of neurofibromatosis

Abstract In the last two decades our knowledge of the natural history, genetics and management of the different forms of neurofibromatosis has changed. Of the numerical classifications of neurofibromatosis proposed in the past, only neurofibromatosis type 1 (Nf1) and neurofibromatosis type 2 (Nf2) have been shown to be distinct at clinical and molecular levels. Mosaicism has been demonstrated both in patients with Nf1 and in patients with Nf2, and features of segmental or mosaic Nf1 and Nf2 have been defined. The outlying phenotypes and the molecular genetics of other, rarer, types of neurofibromatosis have been delineated: these are hereditary spinal neurofibromatosis, Schwannomatosis, familial intestinal neurofibromatosis, autosomal dominant ”café-au-lait spots alone”, autosomal dominant ”neurofibromas alone”, Watson syndrome, Noonan/neurofibromatosis syndrome and the so-called syndrome of multiple naevi, multiple schwannomas and multiple vaginal leiomyomas. In this article I will review the different forms of neurofibromatosis, focusing on those aspects that most commonly challenge the neurosurgeon.

The neurology of coeliac disease in childhood: what is the evidence? A systematic review and meta‐analysis

Aim  The aim of this article was to review and conduct a meta‐analysis of the paediatric literature on the neurology of coeliac disease.

Multiple sclerosis in children under 10 years of age.

Abstract.Despite the consistent amount of information accumulated in recent years on multiple sclerosis (MS) in childhood, many clinicians still view this condition as an exclusively young adult-onset disease and do not consider that it may occur and manifest even during infancy and pre-school age, suggesting that the number of MS cases in the paediatric age group may have been underestimated. Thus, the need to have practical parameters for therapeutic, counselling and educational purposes in such settings as caring for patients whose onset of disease is at very early ages may increasingly arise for practising clinicians. In addition, the clinical and radiographic criteria for the diagnosis of MS have not been validated in a paediatric MS population; accordingly, inclusion age at onset (such as for research purposes) is generally over 10 years. To highlight the peculiarities that characterise MS when it begins at this young age we have reviewed the literature and summarised our preliminary results with the national registry of the Italian Society of Paediatric Neurology (SINP) Study Group on Childhood MS in the group of MS patients with the earliest onset of disease (i. e., <10 years of age).

Addition of verapamil in the treatment of severe myoclonic epilepsy in infancy

We report on the use of the voltage-gated calcium channel blocker (Vg-CCB), verapamil, as an add-on anticonvulsant medication in two girls, 4 and 14 years of age, who were affected by severe myoclonic epilepsy in infancy (SMEI) or Dravet syndrome, a channelopathy caused by abnormalities in the voltage-gated sodium channel neuronal type alpha1 subunit (SCN1A) gene at 2q24. Both girls had pharmacoresistant epilepsy and developmental delay. Mutation analysis for the SCN1A gene revealed a missense mutation in exon 2 in the 4-year-old girl. Verapamil was co-administered in both children with a prompt response in controlling status epilepticus, myoclonic jerks, and partial and generalized seizures. The therapeutic effect lasted 13 months in the 14-year-old girl, while it is still present after a 20-month follow-up period in the 4-year-old girl who, in addition, has experienced improvement in motor and language development. The verapamil vVg-CCB, which crosses the blood-brain barrier (BBB): (a) inhibits the P-glycoprotein, an active efflux transporter protein expressed in normal tissue, including the brain, which is believed to contribute to the in situ phenomenon of multidrug resistance; and (b) may regulate membrane depolarization induced by abnormal sodium channels functions by modulating the abnormal Ca++ influxes into neurons with subsequent cell resting. This is the first report on long-lasting verapamil therapy in SMEI. The functional consequences of such in vivo modulating effects on Ca++ channels could contribute to rational targeting for future molecular therapeutic approaches in pharmacoresistant epileptic channelopathies.

A search for evidence of somatic mutations in the NF1 gene

Neurofibromatosis type I (NF1) is an autosomal dominant disorder affecting 1 in 3000 people. The NF1gene is located on chromosome 17q11.2, spans 350 kb of genomic DNA, and contains 60 exons. A major phenotypic feature of the disease is the widespread occurrence of benign dermal and plexiform neurofibromas. Genetic and biochemical data support the hypothesis thatNF1 acts as a tumour suppressor gene. Molecular analysis of a number of NF1 specific tumours has shown the inactivation of both NF1 alleles during tumourigenesis, in accordance with Knudsons “two hit” hypothesis. We have studied 82 tumours from 45 NF1 patients. Two separate strategies were used in this study to search for the somatic changes involved in the formation of NF1 tumours. First, evidence of loss of heterozygosity (LOH) of the NF1 gene region was investigated, and, second, a screen for the presence of sequence alterations was conducted on a large panel of DNA derived from matched blood/tumour pairs. In this study, the largest of its kind to date, we found that 12% of the tumours (10/82) exhibited LOH; previous studies have detected LOH in 3-36% of the neurofibromas examined. In addition, an SSCP/HA mutation screen identified five novelNF1 germline and two somatic mutations. In a plexiform neurofibroma from an NF1 patient, mutations in bothNF1 alleles have been characterised.