Ilaria Cabrini

Giant axon and neurofilament accumulation in Charcot–Marie–Tooth disease type 2E

The axonal type 2 Charcot–Marie–Tooth disease (CMT2) is phenotypically poorly characterized. Here the authors report a family with a Pro22Ser mutation in the neurofilament-light gene (NF-L; CMT2E) manifesting electrophysiologically as the demyelinating type 1 CMT (CMT1) and pathologically as an axonopathy with giant axons and accumulation of disorganized NF. NF-L should be investigated in CMT2 as well as in CMT1 not associated with the usual genes PMP22, Cx32, and P0.

Two novel mutations in dynamin-2 cause axonal Charcot-Marie-Tooth disease.

Background: Recently, mutations affecting different domains of dynamin-2 (DNM2) were associated alternatively with autosomal dominant centronuclear myopathy or dominant intermediate (demyelinating and axonal) Charcot–Marie–Tooth disease (CMT) type B. Objective: To assess the etiologic role of DNM2 in CMT. Methods: We performed a mutational screening of DNM2 exons 13 through 16 encoding the pleckstrin homology domain in a large series of CMT patients with a broad range of nerve conduction velocities and without mutations in more common genes. Results: We identified two novel DNM2 mutations that cosegregated with purely axonal CMT in two pedigrees without clinical evidence of primary myopathy. Conclusion: Patients with axonal Charcot–Marie–Tooth disease type 2 neuropathy without mutations in more common genes should undergo investigation for DNM2 pleckstrin homology.

Variable presentations of TTR-related familial amyloid polyneuropathy in seventeen patients

Autosomal‐dominant transthyretin (TTR)‐related amyloidosis usually manifests in the second to fourth decade with a length‐dependent axonal neuropathy with prominent involvement of the small fibers and multi‐organ systemic failure. We retrospectively analyzed seventeen probands, including thirteen apparently isolated cases, carrying eight mutations of TTR gene (age of onset = 60.4 ± 13.5 years). Thirteen patients were initially un/misdiagnosed; interval from onset to definite diagnosis was 3.3 ± 2.3 years. Inaugural syndromes were a length‐dependent motor‐sensory neuropathy in seven cases, a sensory neuropathy in four, an isolated carpal tunnel syndrome in three, a pure dysautonomia in two, and a painful neuropathy in one. Atypical presentations included demyelinating nerve conduction changes with increased cerebrospinal fluid proteins resembling chronic inflammatory demyelinating polyradiculoneuropathy and a predominantly motor involvement resembling a motor neuron disorder. Misleading findings also included amyloid‐negative abdominal fat aspirate/biopsy, biclonal gammopathy, and hepatitis C virus (HCV) seropositivity. Sural nerve biopsy detected amyloid deposits in thirteen of fifteen patients, including one case with a previous negative biopsy. TTR‐immunohistochemistry was necessary to complete the diagnosis of primary amyloidosis light chain in a patient with biclonal gammopathy. A recurrent p.Phe64Leu mutation manifested in the seventh decade with painful motor‐sensory polyneuropathy, dysautonomia, bulbar palsies, and fasciculations. TTR should be tested in a wide clinical spectrum of cryptogenetic, progressive, and motor‐sensory neuropathies even manifesting with a very late onset.

Inherited demyelinating neuropathies with micromutations of peripheral myelin protein 22 gene

The peripheral myelin protein 22 gene (PMP22) encodes an intrinsic membrane protein of compact myelin. Duplication or deletion of PMP22 causes the most common autosomal dominant neuropathies, Charcot-Marie-Tooth disease type 1A or hereditary neuropathy with liability to pressure palsies. Charcot-Marie-Tooth disease type 1A is a hypertrophic de-remyelinating neuropathy manifesting with peroneal muscular atrophy and uniform, marked, slowing of nerve conduction velocities. Hereditary neuropathy with liability to pressure palsies is a recurrent focal neuropathy with sausage-like myelin thickening (tomacula) and non-uniform nerve conduction velocity changes. Missense or nonsense mutations also cause more severe Charcot-Marie-Tooth disease type 1A forms of infancy or hereditary neuropathy with liability to pressure palsies, but they are presumably very rare. We performed a mutational scanning of PMP22 in 229 index patients (46 familial, 183 isolated) referred for suspected inherited neuropathy. The series included 125 cases with hereditary neuropathy with liability to pressure palsies (mean age 42.5 years), 47 cases with Charcot-Marie-Tooth disease type 1A (motor nerve conduction velocities at median nerve below 38 m/s) (mean age 40.7 years) and 57 cases with Charcot-Marie-Tooth with unknown nerve conduction velocities (mean age 43 years). Preliminary molecular studies ruled out PMP22 duplication or deletion or mutations in a comprehensive panel of Charcot-Marie-Tooth genes. Mutational scanning of PMP22 was done by denaturing high performance liquid chromatography and automated nucleotide sequencing. To investigate the molecular basis of phenotype-to-genotype correlations, we performed a transcriptional analysis of PMP22 using reverse-transcriptase polymerase chain reaction and quantitative real-time polymerase chain reaction in two phenotypically divergent nerve biopsies. Ten patients harboured eight micromutations of PMP22 including four novel changes. In six familial and three sporadic cases, detected mutations caused premature or delayed stop codons and were associated with hereditary neuropathy with liability to pressure palsies; the related pathological pictures ranged from classical tomaculous neuropathy to a mild demyelinating neuropathy with atypical non-tomaculous myelin thickenings. In a single family a c.179-2A> G mutation affecting the splice acceptor site of intron 2 cosegregated with a Charcot-Marie-Tooth disease type 1A-like syndrome and a peculiar pathological picture of demyelinating neuropathy without Charcot-Marie-Tooth disease type 1A-like classical onion bulbs or tomacula. Transcriptional analysis of a novel c.174_178 + 7delAAACGGTGAGGC deletion involving exon 2 and intron 2 demonstrated an unstable mutant transcript leading to a p.Asn59GlyfsX12 change; the mutation represented a null allele and caused a typical tomaculous hereditary neuropathy with liability to pressure palsies. The Charcot-Marie-Tooth disease type 1-like c.179-2A > G allele led to a stable transcript with an in-frame deletion of exon 3 (p.Glu60_Ala106del); the predicted shorter protein could exert variable molecular effects. In conclusion, micromutations of PMP22 cause a clinical and pathological continuum of demyelinating neuropathies that may include atypical phenotypes.

Polyneuropathy with anti-sulfatide and anti-MAG antibodies: Clinical, neurophysiological, pathological features and response to treatment

IgM paraproteins often present reactivity to myelin-associated glycoprotein (MAG) and sulfatide. We describe the clinical and neurophysiological findings, and therapy response in 21 patients with IgM paraproteinemic neuropathy (15 with anti-MAG antibodies, 1 with anti-sulfatide antibodies, and 5 with both reactivity), and in 2 with anti-sulfatide positivity and no hematological disease. All patients complained of sensory symptoms, the majority had demyelinating neuropathy. Indirect immunofluorescence on human normal sural nerves disclosed different staining patterns. Eight of 13 patients (6 anti-MAG, 1 anti-sulfatide, 1 both anti-sulfatide and anti-MAG antibodies) improved after Rituximab. IVIg, steroids and plasma-exchange were also administered with different responses.

Gene dosage sensitivity of a novel mutation in the intracellular domain of P0 associated with Charcot-Marie-Tooth disease type 1B.

Autosomal dominant Charcot-Marie-Tooth disease type 1B (CMT1B) is caused by heterozygous mutations in the extracellular domain of P0. Here, we investigated clinically, electrophysiologically and pathologically a pedigree with a novel mutation in the intracellular domain of P0 (P0ic). The mutational analysis included denaturing high performance liquid chromatography (DHPLC) and nucleotide sequencing. Two patients from subsequent generations were homozygous for an Asp195Tyr mutation in the intracellular domain of P0 (P0ic), whereas two healthy individuals with minimal electrophysiological changes were heterozygous for the same mutation. The authors conclude that mutations of P0ic may undergo a gene dosage effect manifesting semidominant inheritance.

Pentraxin-3 and VEGF in POEMS syndrome: a 2-year longitudinal study.

Circulating Pentraxin 3 (PTX3) and vascular endothelial growth factor (VEGF) levels were measured longitudinally (mean follow-up 2 years) by ELISA in 6 patients with polyneuropathy, organomegaly, endocrinopathy, M-protein, skin changes (POEMS) syndrome and 16 controls. Expression of PTX3 was also assessed (immunohistochemistry) on sural nerve biopsies from POEMS and vasculitic neuropathy patients. No correlation was found between PTX3 and VEGF levels in POEMS or controls. Sural nerve biopsies from vasculitic neuropathy patients, but not those from POEMS syndrome, showed strong PTX3 staining. PTX3, expression of vessel inflammation/remodeling, and VEGF, crucial pro-angiogenic cytokine, appear to be independently regulated in POEMS syndrome.

Parental mosaicism of a novel PMP22 mutation with a minimal neuropathic phenotype

Genetic germinal and somatic mosaicisms of dominant Charcot‐Marie‐Tooth disease (CMT) mutations are rarely reported and/or recognized. We describe a novel heterozygous p.Trp39Cys missense mutation in the extracellular domain of the peripheral myelin protein 22 (PMP22) associated with an early‐onset demyelinating CMT type 1 E (CMT1E) in two siblings born from asymptomatic non‐consanguineous parents. The 29‐year‐old mother, harboring approximately 20% of the mutant PMP22 allele in blood, had minor signs of distal polyneuropathy (pes cavus, decreased ankle jerk reflexes and vibration sense in legs) and slight reduction of sural nerve action potentials (SNAPs). Authors suggest that mutations of CMT‐related genes which originate in post‐zygotic stages may be associated with mild phenotypes of peripheral neuropathy.

Déjerine-Sottas syndrome with a silent nucleotide change of myelin protein zero gene.

Charcot‐Marie‐Tooth disease type 1B (CMT1B) and Déjerine‐Sottas syndrome type B (DSSB) are caused by missense or frameshift mutations of myelin protein zero (MPZ) gene. We identified an apparently silent synonymous c.411C>T transition in MPZ exon 3 (p.Gly137Gly) which segregated with DSS in a two‐generation pedigree. Retro‐transcriptional analysis of MPZ in the probands archive sural nerve biopsy identified an r.410_448del mutant transcript which resulted from an activated cryptic splice site in exon 3 and led to an in‐frame partial deletion of exon 3 (p.Gly137_Lys149del). Quantitative real‐time polymerase chain reaction (QRT‐PCR) compared with two unrelated CMT1B nerves carrying a frameshift c.306delA mutation (p.Asp104ThrfsX13) indicated that the r.410_448del was stable differing from the p.Asp104ThrfsX13‐associated transcript which was subjected to nonsense‐mediated decay. The report highlighted the possible pathogenic role of synonymous MPZ mutations and difficulties in interpreting results from routine mutational screenings.

Primary neurolymphomatosis as clinical onset of chronic lymphocytic leukemia

Dear Editor, A 58-year-old woman sought neurological advice for a 3-month history of paresthesias at the lower limbs and unsteady gait. She had mild distal weakness at the legs, tactile hypoestesia up to the left knee, and absent Achilles tendon reflexes. Electrodiagnostic studies revealed axonal sensory-motor multineuropathy. Complete blood count showed a mild lymphocytosis (7000 cells/ μL). Immunophenotype detected a clonal lambda B cell population expressing CD5+, CD20dim, CD23+, and low immunoglobulin surface levels, consistent with chronic lymphocytic leukemia (CLL). Cerebrospinal fluid (CSF) was unremarkable (protein 35 mg%, 408 RBC/ μL, 1.3 WBC/μL). At CSF immunophenotype, 47 % of lymphocytes were B CD5+ cells, likely related to blood CSF contamination. Molecular analyses on circulating CLL cells showed mutated conformation of the IGVH gene of the B cell receptor (homology <98 % from the germline sequence); cytogenetic studies showed trisomy of chromosomes 12, 18, and 19 and deletion of 11q at FISH and wild-type status of TP53 and NOTCH1. The co-existence of trisomies of chromosome 12 and 19 has been recently demonstrated to be enriched in young CLL patients (median age 59 years) and to be associated with indolent clinical course [1]. Sural nerve biopsy showed endoneural perivascular infiltration of CD20 and CD5+ lymphomonocytes. Semithin sections showed reduced density of myelin fibers (Fig. 1). Total-body CT scan was negative. CLL-neurolymphomatosis was diagnosed. Before starting therapy, a further neurophysiological evaluation together with nerve ultrasound was performed. Electrodiagnostic study confirmed axonal sensory-motor multineuropathy. Nerve ultrasound revealed a preserved nerve cross-sectional area and echogenicity, but color Doppler sonography showed increased perineural and intraneural vascularity at the left tibial nerve in the popliteal fossa (Fig. 2a). The early stage and the biological low-risk profile of the disease oriented us on therapy with rituximab alone. After 8 cycles of rituximab (375 mg/m IV), paresthesias significantly decreased and gait regained functionality. At Doppler ultrasound, blood flow was absent (Fig. 2b). Neurolymphomatosis is a rare and often overlooked diagnosis [2–5]. Histological demonstration of nerve infiltration is mandatory for a certain diagnosis, but neuroimaging is increasingly gaining a diagnostic role [6–9]. Ultrasound has already been described as useful for identifying peripheral nerve involvement in B cell lymphoma [10, 11], but histological confirmation is needed, since increased nerve blood flow can be found also in active chronic inflammatory demyelinating polyradiculoneuropathy [12]. The patients described by * Chiara Briani chiara.briani@unipd.it