Adult-onset mitochondrial movement disorders: a national picture from the Italian Network.

INTRODUCTION: Both prevalence and clinical features of the various movement disorders in adults with primary mitochondrial diseases are unknown. METHODS: Based on the database of the "Nation-wide Italian Collaborative Network of Mitochondrial Diseases", we reviewed the clinical, genetic, neuroimaging and neurophysiological data of adult patients with primary mitochondrial diseases (n = 764) where ataxia, myoclonus or other movement disorders were part of the clinical phenotype. RESULTS: Ataxia, myoclonus and movement disorders were present in 105/764 adults (13.7%), with the onset coinciding or preceding the diagnosis of the mitochondrial disease in 49/105 (46.7%). Ataxia and parkinsonism were the most represented, with an overall prevalence at last follow-up of 59.1% and 30.5%, respectively. Hyperkinetic movement disorders were reported in 15.3% at last follow-up, being the less common reported movement disorders. The pathogenic m.8344A > G and POLG variants were always associated with a movement disorder, while LHON variants and mtDNA single deletions were more commonly found in the subjects who did not present a movement disorder. The most common neuroimaging features were cortical and/or cerebellar atrophy, white matter hyperintensities, basal ganglia abnormalities and nigro-striatal degeneration. Almost 70% of patients with parkinsonism responded to dopaminergic therapy, mainly levodopa, and 50% with myoclonus were successfully treated with levetiracetam. CONCLUSION: Movement disorders, mainly ataxia and parkinsonism, are important findings in adult primary mitochondrial diseases. This study underlies the importance of looking for a mitochondrial etiology in the diagnostic flowchart of a movement disorder and may help direct genetic screening in daily practice.

Clinical and neuroimaging features of the m.10197G>A mtDNA mutation: New case reports and expansion of the phenotype variability.

Complex I (CI) is the largest component of the mitochondrial respiratory chain (MRC) and it is made up of 7 mitochondrial DNA (mtDNA)-encoded and at least 38 nuclear DNA-encoded subunits. Isolated CI deficiency is the most common single enzyme deficiency in the heterogeneous group of MRC disorders and it is a relatively common etiology of Leigh-like syndrome (LS). With a few exceptions, descriptions of the clinical spectrum of specific mutations in CI are scarce. We here present three unrelated Italian children who harbored the homoplasmic m.10197G>A mutation in MT-ND3 associated with reduced enzyme activity of CI in muscle. Compared with the spectrum of phenotypes seen in 13 previously described families with the same mutation, these children showed some novel clinical features. Two of the boys presented with subacute onset of dystonia, which showed a remitting-relapsing clinical course in one of them. The third boy presented acute symptoms consisting of speech impairment, progressive left-sided hemiparesis, and also vertebral and arterial malformations. In all the children, molecular studies identified a similar mutation load in tissues, and neuroimaging findings were consistent with the features seen in LS. Functional investigations in cultured skin fibroblasts suggested low ATP production in homoplasmic cells. Our results confirm that the m.10197G>A mutation is relevant to these patients' clinical and biochemical phenotypes, which thus expand the array of phenotypes associated with this variant.

Prevalence and phenotype of the c.1529C>T SPG7 variant in adult-onset cerebellar ataxia in Italy.

BACKGROUND AND PURPOSE: Hereditary ataxias are heterogeneous groups of neurodegenerative disorders, characterized by cerebellar syndromes associated with dysarthria, oculomotor and corticospinal signs, neuropathy and cognitive impairment. Recent reports have suggested mutations in the SPG7 gene, causing the most common form of autosomal recessive spastic paraplegia (MIM#607259), as a main cause of ataxias. The majority of described patients were homozygotes or compound heterozygotes for the c.1529C>T (p.Ala510Val) change. We screened a cohort of 895 Italian patients with ataxia for p.Ala510Val in order to define the prevalence and genotype-phenotype correlation of this variant. METHODS: We set up a rapid assay for c.1529C>T using restriction enzyme analysis after polymerase chain reaction amplification. We confirmed the diagnosis with Sanger sequencing. RESULTS: We identified eight homozygotes and 13 compound heterozygotes, including two novel variants affecting splicing. Mutated patients showed a pure cerebellar ataxia at onset, evolving in mild spastic ataxia (alternatively) associated with dysarthria (~80% of patients), urinary urgency (~30%) and pyramidal signs (~70%). Comparing homozygotes and compound heterozygotes, we noted a difference in age at onset and Scale for the Assessment and Rating of Ataxia score between the two groups, supporting an earlier and more severe phenotype in compound heterozygotes versus homozygotes. CONCLUSIONS: The SPG7 c.1529C>T (p.Ala510Val) mutants accounted for 2.3% of cerebellar ataxia cases in Italy, suggesting that this variant should be considered as a priority test in the presence of late-onset pure ataxia. Moreover, the heterozygous/homozygous genotype appeared to predict the onset of clinical manifestation and disease progression.

Revisiting mitochondrial ocular myopathies: a study from the Italian Network.

Ocular myopathy, typically manifesting as progressive external ophthalmoplegia (PEO), is among the most common mitochondrial phenotypes. The purpose of this study is to better define the clinical phenotypes associated with ocular myopathy. This is a retrospective study on a large cohort from the database of the "Nation-wide Italian Collaborative Network of Mitochondrial Diseases". We distinguished patients with ocular myopathy as part of a multisystem mitochondrial encephalomyopathy (PEO-encephalomyopathy), and then PEO with isolated ocular myopathy from PEO-plus when PEO was associated with additional features of multisystemic involvement. Ocular myopathy was the most common feature in our cohort of mitochondrial patients. Among the 722 patients with a definite genetic diagnosis, ocular myopathy was observed in 399 subjects (55.3%) and was positively associated with mtDNA single deletions and POLG mutations. Ocular myopathy as manifestation of a multisystem mitochondrial encephalomyopathy (PEO-encephalomyopathy, n = 131) was linked to the m.3243A>G mutation, whereas the other "PEO" patients (n = 268) were associated with mtDNA single deletion and Twinkle mutations. Increased lactate was associated with central neurological involvement. We then defined, among the PEO group, as "pure PEO" the patients with isolated ocular myopathy and "PEO-plus" those with ocular myopathy and other features of neuromuscular and multisystem involvement, excluding central nervous system. The male proportion was significantly lower in pure PEO than PEO-plus. This study reinforces the need for research on the role of gender in mitochondrial diseases. The phenotype definitions here revisited may contribute to a more homogeneous patient categorization, useful in future studies and clinical trials.

Identification of mutations in AP4S1/SPG52 through next generation sequencing in three families.

BACKGROUND AND PURPOSE: The term hereditary spastic paraplegia (HSP) covers a spectrum of genetically heterogeneous disorders in which lower limb spasticity is the common clinical feature. Many patients with childhood-onset HSP are mistakenly diagnosed with cerebral palsy (CP). METHODS: A group of as yet molecularly undiagnosed HSP patients were analyzed using SpastoPlex, a customized target re-sequencing panel able to investigate the coding regions of 72 genes linked to HSP, spastic ataxias or related motor diseases. RESULTS: Our investigations identified loss-of-function mutations in AP4S1/SPG52 in four children (three families) who had previously received a diagnosis of diplegic/quadriplegic CP. The patients presented spastic paraparesis, mild facial dysmorphisms, moderate-to-severe intellectual disability and severe speech delay. Two patients manifested febrile seizures and childhood-onset focal seizures. In all the patients, brain magnetic resonance imaging (MRI) showed a peculiar hypoplastic posterior corpus callosum, often associated with ventriculomegaly, white matter loss and cerebral atrophy. CONCLUSION: Adaptor protein 4 (AP-4) deficiency disorders should be suspected in children with spastic paraparesis, cognitive deficit and absent speech accompanied by suggestive MRI features. Seizures might be amongst the clinical manifestations of the syndrome.

Tarlov cysts: clinical evaluation of an italian cohort of patients.

Tarlov cyst syndrome is a rare, often asymptomatic disorder, characterised by isolated or multiple nerve-root cysts, usually occurring in the sacral spine, near the dorsal root ganglion, between the perineurium and endoneurium. The cysts may cause lower back pain, sacral radiculopathy, dyspareunia and urinary incontinence. There is little data in the literature on the relationship between Tarlov cysts and symptoms. Here, we report further details on the clinical impact of Tarlov cysts and investigate their pathogenesis and role as a cause of lumbosacral symptoms. We examined 157 patients with MRI evidence of symptomatic Tarlov cysts. Patients underwent complete neurological examination and were scored by the Hamilton Depression Rating Scale and the Visual Analogue Scale. Complete lower limb electromyography was performed in 32 patients. Clinical picture was correlated with size and number of cysts detected by MRI. Family history was recorded for signs of genetic inheritance. Almost all patients suffered perineal or lower back pain; 34 complained of sphincter and 46 of sexual disorders. Hamilton scores were abnormal, and family history was positive in a few cases. The scanty literature on Tarlov cysts mainly regards therapy by a neurosurgical approach. Our results provide new data on clinical impact and possible pathogenetic mechanisms.

Chronic progressive external ophthalmoplegia: a new heteroplasmic tRNA(Leu(CUN)) mutation of mitochondrial DNA.

We sequenced all genes of mitochondrial tRNAs of a patient with chronic progressive external ophthalmoplegia with 5% ragged red fibres and 15% COX-negative fibres but without macrorearrangements of mitochondrial DNA (mtDNA). Direct sequencing showed a novel heteroplasmic G>A substitution in position 12316 of tRNA(Leu(CUN)) gene. This change destroys a highly conserved G-C base coupling in tRNA TpsiC branch. By RFLP analysis we could demonstrate different degrees of heteroplasmy in different patient's tissues. This alteration, absent in a population of 110 patients with different encephalomyopathies, can be considered pathogenic: it is the tenth tRNA(Leu(CUN)) pathogenic mutation described up to date.