Hereditary Motor-Sensory Neuropathies: Charcot-Marie-Tooth Syndrome

Surgical treatment of cavus foot in Charcot-Marie-tooth disease: a review of twenty-four cases: AAOS exhibit selection

Charcot-Marie-Tooth disease is the single most common diagnosis associated with cavus foot. The imbalance involving intrinsic and extrinsic muscles has been suggested as the main pathogenetic cause of cavus foot in this disease. The goal of surgical treatment is to correct the deformity to obtain a plantigrade foot. In the presence of a flexible deformity and the absence of degenerative arthritis, preserving as much as possible of the overall range of motion of the foot and ankle is advisable. Twenty-four cavus feet in twelve patients with Charcot-Marie-Tooth disease were included in the study. Clinical evaluation was summarized with the Maryland Foot Score. Radiographic evaluation assessed calcaneal pitch, Meary angle, Hibb angle, and absence of degenerative joint changes. Only patients who had a flexible deformity, with varus of the heel reducible in the Coleman-Andreasi test, and did not have degenerative joint arthritis were included in this study. Surgical treatment consisted in plantar fasciotomy, midtarsal osteotomy, extensor hallucis longus tendon transfer to the first metatarsal (Jones procedure), and dorsiflexion osteotomy of the first metatarsal. Mean follow-up was six years (range, two to thirteen years). The mean Maryland Foot Score was 72 preoperatively and 86 postoperatively. The postoperative result was rated as excellent in twelve feet (50%), good in ten (42%), and fair in two (8%). Mean calcaneal pitch was 34° preoperatively and 24° at the time of the latest follow-up, the mean Hibb angle was 121° preoperatively and 136° postoperatively, and the mean Meary angle was 25° preoperatively and 2° postoperatively. Plantar fasciotomy, midtarsal osteotomy, the Jones procedure, and dorsiflexion osteotomy of the first metatarsal yielded adequate correction of flexible cavus feet in patients with Charcot-Marie-Tooth disease in the absence of fixed hindfoot deformity. The fact that the improvement in the outcome score was only modest may be attributable to the lack of motor balance.

A novel LRSAM1 mutation is associated with autosomal dominant axonal Charcot-Marie-Tooth disease

Charcot-Marie-Tooth (CMT) disease is the most common hereditary neuropathy resulting from mutations in >30 genes expressed in either the Schwann cells or the axon of peripheral nerves. The disease is classified into demyelinating (CMT1), axonal (CMT2) or intermediate (CMTI) based on electrophysiological and pathological findings. Our study focused on the identification of a novel disease mutation in a large Sardinian family with CMT2 of autosomal dominant (AD) inheritance. All available family members were clinically evaluated and samples were collected from consenting individuals. Initially, we excluded known CMT2 genes/loci in this family. We then conducted a genome-wide linkage analysis and mapped the gene to chromosome 9q33-q34. Refined linkage and haplotype analyses defined an 11.6-Mb candidate region with a maximum LOD score of 8.06. Following exclusion of several candidate genes from the region, we targeted the LRSAM1 (leucine-rich repeat and sterile alpha motif-containing 1) gene, very recently found to be associated with autosomal recessive CMT2 in one family. For a more efficient investigation of this large gene, already available proband RNA (cDNA) was initially analyzed. Targeted DNA analysis then confirmed a novel LRSAM1 splice-site (c.2047-1G>A) mutation, causing a frameshift that introduces a stop codon three amino acids further down the new reading frame (p.Ala683ProfsX3). This mutation is located in the C-terminal RING finger motif of the encoded protein and leads to premature truncation of the protein. In the course of our work, a second LRSAM1 mutation dominantly transmitted was identified by another group. Our data further confirms that LRSAM1 mutations are associated with CMT2 of AD inheritance.

Low dose vincristine-induced severe polyneuropathy in a Hodgkin lymphoma patient: a case report (vincristine-induced severe polyneuropathy)

Chemotherapeutic drugs are the most common toxic agents for peripheral nerves. Vincristine is a vinca alkaloid drug that is used for the treatment of several malignancies in combination with other chemotherapeutic agents. Treatment with intravenous (IV) vincristine at doses above 5 mg leads to a dose-dependent neuropathy with sensory symptoms but higher cumulative doses at around 30 to 50 mg are needed for the development of motor symptoms. The standard maximum adult IV vincristine dose is 2 mg IV per dose given at weekly intervals. However, administration of a single 2-mg dose IV vincristine may rarely result in the development of peripheral neuropathy. Few case reports have been presented on vincristine-associated severe paralysis in patients with preexisting hereditary neuropathy like Charcot-Marie Tooth (CMT) disease, who received doses even lower than 2 mg. Herein, we reported a Hodgkin lymphoma patient who developed severe polyneuropathy after receiving 2 mg vincristine treatment and was subsequently found to carry the CMT1A duplication responsible for CMT disease.

Severe vincristine neuropathy in Charcot-Marie-Tooth disease type 1A

BACKGROUND

A general predisposition for vincristine-related neuropathy has been observed in persons with a family history of hereditary neuropathies.

METHODS

In a retrospective case series, we investigated the possible association between the DNA rearrangement found in patients with Charcot-Marie-Tooth Disease Type 1A (CMT1A) and susceptibility to the neurotoxicity of vincristine. In selected patients and family members, we performed electrodiagnostic studies and analyzed DNA samples for 17p11.1-12 duplication associated with CMT1A.

RESULTS

We describe three families with autosomal dominant CMT1, among whom a family member with a neoplastic disease suffered rapid onset, severe neuropathy after receiving initial doses of vincristine as a part of a routine chemotherapy protocol. All three families had at least one affected family member with 17p11.2-12 duplication.

CONCLUSIONS

These cases show that 17p11.2-12 duplication predisposes patients to severe neurotoxicity from vincristine and that this drug should be avoided with patients with CMT1A. It is therefore essential to obtain a detailed family history for all oncology patients to screen for possible hereditary neuropathies. In patients with unexplained or preexisting familial neuropathy, testing for 17p11.2-12 duplication should be carried out prior to initiating vincristine therapy. Patients with other hereditary neuropathies may also be at risk for severe neurotoxic reactions.

The Charcot-Marie-Tooth syndrome: clinical aspects from a population study in South Wales, UK

The Charcot-Marie-Tooth (CMT) syndrome comprises a heterogeneous group of disorders affecting the peripheral nerves and anterior horn cells of the spinal cord. They constitute a significant proportion of the burden of disability caused by single gene neurological disorders, with a disease prevalence of 16.7 per 10(5) of the South Wales adult population. The clinical and genetic characteristics of these diseases in the population are described. In those cases identified as type I hereditary motor and sensory neuropathy (HMSN I), we have shown that it is possible to correlate disease severity with age, and that there is no clinical evidence for imprinting, manifest either in age of onset or disease severity.

Charcot-Marie-Tooth disease in northern Sweden: an epidemiological and clinical study

One hundred four cases of Charcot-Marie-Tooth disease (CMT) in 52 families were identified within a defined area in northern Sweden corresponding to a prevalence rate of 20.1 cases per 100,000 (Dec 31 1991) for all subtypes. The prevalence of CMT type I was 16.2 per 100,000. The distribution of cases was not uniform. The prevalence rate is compared with previous prevalence studies focusing on Charcot-Marie-Tooth disease or hereditary motor and sensory neuropathy (HMSN). Three patients were classified as the distal spinal muscular atrophy type of CMT and one patient was not possible to classify. For seventy-five patients, available to clinical examination within the study, data were collected as to age at onset, symptoms, clinical findings and degree of disability.

Molecular genetics and neuropathology of Charcot-Marie-Tooth disease type 1A

Charcot-Marie-Tooth (CMT) syndrome describes a genetically and clinically heterogeneous group of polyneuropathies. Electrophysiologically, at least two types of CMT can be distinguished; CMT1 which has decreased nerve conduction velocities (NCV) and CMT2 which has normal or near normal NCV with decreased amplitudes. For CMT1, three gene loci (on chromosomes 1, 17 and the X chromosome) have been mapped. The locus on chromosome 17, CMT type 1A (CMT1A), is responsible for the most common form of CMT which has recently been shown to be associated with a large DNA duplication. Recent data demonstrates that the CMT1A phenotype results from an inherited DNA rearrangement and a gene dosage effect. The trembler (Tr) and allelic tremblerJ (TrJ) mice have been proposed as animal models for CMT. Tr has similar electrophysiological and neuropathological features to CMT1 patients and maps to mouse chromosome 11 in a region of conserved synteny with human chromosome 17p. Tr and TrJ have recently been shown to have different point mutations in regions encoding putative transmembrane domains of the myelin specific protein PMP-22. The human peripheral nerve-specific PMP-22 gene maps within the CMT1A duplication. PMP-22 is thus a candidate gene for CMT1A. This paper describes the molecular genetics of CMT1A and sural nerve pathology in CMT1A patients with the CMT1A duplication.

Charcot-Marie-Tooth disease type 1a (CMT1a): evidence for trisomy of the region p11.2 of chromosome 17 in south Wales families

The gene for Charcot-Marie-Tooth disease type 1a (CMT1a) has been localised to chromosome 17p11.2. Locus D17S122 is recognised by the DNA probe pVAW409R3 which detects an MspI polymorphism with three alleles in the normal population. Subjects with CMT1a show evidence of trisomy for this region of chromosome 17 by displaying either all three alleles or a dosage effect when only two alleles are present. This phenomenon was seen in 10 out of 11 families with type I hereditary motor and sensory neuropathy (HMSN) where affected subjects were heterozygous for the MspI polymorphisms. This mutation is likely to have arisen from a non-reciprocal recombination event between non-sister chromatids of homologous chromosomes at meiosis I. The detection of this partial trisomy offers a rapid method for the diagnosis of CMT1a in families not suitable for linkage analysis.