Transthyretin amyloidosis: A new mutation associated with dementia

Familial transthyretin (TTR) amyloidosis commonly presents with peripheral neuropathy and involvement of visceral organs. In contrast, signs of central nervous system (CNS) involvement are exceptional. We report that members of a kindred affected by a slowly progressive dementia, seizures, ataxia, hemiparesis, and decreased vision without neuropathy have TTR amyloid deposits in the leptomeninges, the brain parenchyma, and the eye. This condition, previously labeled oculoleptomeningeal amyloidosis, is linked to a mutation at codon 30 of TTR gene, resulting in the substitution of valine with glycine in this family, TTR amyloid deposits were present in the leptomeninges, especially the leptomeningeal vessels, and in the subependymal regions of the ventricular system where they disrupted the ependymal lining and resulted in amyloid-glial formations protruding into and narrowing the ventricular system. Hydrocephalus and atrophy and infarction of cerebral and cerebellar cortexes were also present. Review of the literature shows that amyloid deposition in the leptomeninges is not uncommon in TTR amyloidoses clinically characterized by peripheral neuropathy and lack of CNS signs. The present kindred, which presented exclusively with signs of CNS involvement, expands the phenotype of TTR amyloidosis and raises questions concerning the mechanisms determining phenotypic expression in TTR familial amyloidosis.     

Familial basilar migraine associated with a new mutation in the ATP1A2 gene

Basilar migraine (BM), familial hemiplegic migraine (FHM), and sporadic hemiplegic migraine (SHM) are phenotypically similar subtypes of migraine with aura, differentiated only by motor symptoms, which are absent in BM. Mutations in CACNA1A and ATP1A2 have been found in FHM. The authors detected a novel mutation in the ATP1A2 gene (R548H) in members of a family with BM, suggesting that BM and FHM may be allelic disorders.     

A previously undescribed leukodystrophy in Leigh syndrome associated with T9176C mutation of the mitochondrial ATPase 6 gene

We report two male Taiwanese siblings in whom the T-->C point mutation at nucleotide 9176 of the mitochondrial ATPase 6 gene (m.9176T>C mutation) was associated with early onset hypotonia, lactic acidosis, and death due to respiratory arrest at 7 and 10 months old. Brain MRI showed lesions over diffuse white matter and the bilateral posterior limbs of the internal capsule. The m.9176T>C mutation is suggested as the cause of the bilateral striatal necrosis and Leigh syndrome. However, leukodystrophy in Leigh syndrome associated with m.9176T>C mutation has never been reported before. We suggest that m.9176T>C mutation could be a new aetiology for leukodystrophy in children with Leigh syndrome.     

A novel GABRG2 mutation associated with febrile seizures

Mutations in the gene encoding the gamma2 subunit of the gamma-aminobutyric acid type A receptor (GABRG2) have been reported to cause childhood absence epilepsy (CAE), febrile seizures (FS), and generalized epilepsy with FS plus (GEFS+). The authors analyzed GABRG2 in 47 unrelated patients with CAE, FS, and GEFS+ and identified a novel mutation that cosegregated with FS. Electrophysiologic studies demonstrated altered current desensitization and reduced benzodiazepine enhancement in mutant receptors.     

A SURF1 gene mutation presenting as isolated leukodystrophy.

Mitochondrial respiratory chain defects are increasingly recognized in patients with leukodystrophy. We report the first case of leukodystrophy with systemic cytochrome oxidase deficiency caused by a loss of function mutation in the SURF1 gene in a 2-year-old girl presenting with failure to thrive, global neurodevelopmental regression, and lactic acidosis. Although all previously reported mutations in the SURF1 gene have been found in patients with cytochrome oxidase (COX)-deficient Leigh syndrome, the phenotype associated with SURF1 protein deficiency should be extended to include leukodystrophy.     

A point mutation associated with a severe phenotype of neurofibromatosis 2

Neurofibromatosis 2 (NF2) is an autosomal dominant disease characterized by bilateral vestibular schwannomas and other nonmalignant tumors of the brain, spinal cord, and peripheral nerves. Although the average age of onset of NF2 is 20 years, some individuals may become symptomatic in childhood. We studied 5 unrelated NF2 patients who became symptomatic before age 13. All 5 had multiple tumors in addition to vestibular schwannoma, and none had a positive family history. Sequence analysis of the NF2 gene revealed identical nonsense mutation of exon 6 in 3 patients. Because this mutation destroys a restriction site, genomic DNA from the 2 other children was directly tested for this change and identical alterations were detected. Although the work of our laboratory and others has not, in general, detected identical mutations in unrelated patients, this mutation seems to occur particularly frequently in the pediatric population and thus may be associated with an especially severe phenotype. Restriction analysis in children with NF2 may be a cost effective way of identifying their mutation. Further work is needed to characterize the effects of this change on the NF2 protein product and its relationship to this severe phenotype.     

A recurrent TMEM106B mutation in hypomyelinating leukodystrophy: A rapid diagnostic assay

IntroductionHypomyelinating leukodystrophies (HLDs) are genetically heterogeneous syndromes, presenting abnormalities in myelin development in the central nervous system. Recently, a recurrent de novo mutation in TMEM106B was identified to be responsible for five cases of HLD. We report the first Japanese case of TMEM106B gene mutation.Case StudyA 3-year-old patient presented with nystagmus and muscle hypotonia in his neonatal period, followed by delayed psychomotor development. Brain magnetic resonance images showed delayed myelination. Wave III and subsequent components were not presented by his auditory brainstem response. These features were similar to those observed in Pelizaeus-Merzbacher disease (PMD).MethodsProteolipid protein 1 (PLP1) gene screening, Mendelian disease panel exome, and whole-exome sequencing (WES) were sequentially performed.ResultsAfter excluding mutations in either PLP1 or other known HLD genes, WES identified a mutation c.754G > A, p.(Asp252Asn) in TMEM106B, which appeared to occur de novo, as shown by Sanger sequencing and SalI restriction enzyme digestion of PCR products.DiscussionThis is the sixth case of HLD with a TMEM106B mutation. All six cases harbored the same variant. This specific TMEM106B mutation should be investigated when a patient shows PMD-like features without PLP1 mutation. Our PCR-SalI digestion assay may serve as a tool for rapid HLD diagnosis.     

Episodic coma in a new leukodystrophy

Among the leukodystrophies of a hypomyelinating nature, childhood ataxia with diffuse central nervous system hypomyelination exhibits the unique feature of rapid decrease in mental status after relatively minor head injuries or otherwise noncomplicated febrile illnesses. This article reports the case of a child with progressive spastic quadriparesis in whom unconsciousness developed repeatedly as a result of minor head trauma and required prolonged critical-care nursing. Although cognition is believed to be relatively preserved in this disorder, this child developed progressive cognitive decline. A detailed review of the literature is presented along with discussion of the potential mechanisms of neurologic deterioration.     

Septo-optic dysplasia associated with a new mitochondrial cytochrome b mutation

We report on a 25-year-old patient with isolated mitochondrial complex III deficiency and a new heteroplasmic mutation (T14849C) in the cytochrome b gene. He suffered from septo-optic dysplasia, retinitis pigmentosa, exercise intolerance, hypertrophic cardiomyopathy, and rhabdomyolysis. A HESX1 mutation was excluded as a cause of his septo-optic dysplasia. Low alpha-tocopherol concentrations in his muscles and an elevated urinary leukotriene E(4) excretion indicate increased production of reactive oxygen species.     

IGHMBP2 mutation associated with organ-specific autonomic dysfunction

Biallelic mutations in the IGHMBP2 have been associated with two distinct phenotypes: spinal muscular atrophy with respiratory distress type 1 (SMARD1) and CMT2S. We describe a patient who developed progressive muscle weakness and wasting in her upper and lower limbs from infancy. She developed respiratory involvement at age 9, eventually requiring 24-h non-invasive ventilation, and severe autonomic dysfunction restricted to the gastrointestinal tract. Neurophysiological studies at age 27 years revealed absent sensory and motor responses and severe chronic denervation changes in proximal muscles of the upper limbs. Targeted multigene panel sequencing detected a novel homozygous missense variant in the IGHMBP2 gene (c.1325A > G; p.Tyr442Cys). This variant was validated by Sanger sequencing and co-segregation analysis confirmed that both parents were asymptomatic heterozygous carriers. This case report confirms that IGHMBP2 related disorders can result in a severe peripheral neuropathy with gastrointestinal autonomic dysfunction requiring parenteral nutrition.     

A new truncating MPZ mutation associated with a very mild CMT1 B phenotype

We have investigated a 34-year-old female who had mild clinical and electrophysiological features of demyelinating peripheral neuropathy. She presented a novel frameshift mutation (V160fsX3) in the exon 4 of the Myelin Protein Zero (MPZ) gene. Clinical and genetic studies performed on her family revealed the same mutation in her oligosymptomatic mother and sister. Our report expands the number of MPZ mutations and indicates that mutations in exon 4 may cause a mild Charcot–Marie–Tooth type 1B phenotype.     

A new mtDNA mutation associated with a progressive encephalopathy and cytochrome c oxidase deficiency

The authors describe a novel pathogenic G5540A transition in the mitochondrial transfer RNA (tRNA)Trp gene of a sporadic encephalomyopathy characterized by spinocerebellar ataxia. Clinical features also included neurosensorial deafness, peripheral neuropathy, and dementia. Biochemistry revealed a severe reduction of cytochrome c oxidase (COX) activity. Single-fiber PCR demonstrated higher levels of mutant genomes in COX-negative ragged red fibers than in normal fibers. These findings confirm that COX is more susceptible than other respiratory chain complexes to mutations in the mitochondrial tRNATrp gene.     

Canavan's leukodystrophy is associated with defects in cochlear neurodevelopment and deafness

The authors present the temporal bone histopathology of two siblings (4 months old and 6 months old at autopsy) with Canavan's disease, an autosomal recessive leukodystrophy that is variably associated with sensorineural hearing loss. The histopathology demonstrated bilateral absence of the organ of Corti throughout the apical and basal cochlea and mild secondary atrophy of the spiral ganglia neurons. The vestibular end organs and ganglia were normal. These findings implicate a role of aminoacylase II in the neurodevelopment of the organ of Corti.