Novel variants broaden the phenotypic spectrum of PLEKHG5-associated neuropathies.

BACKGROUND AND PURPOSE: Pathogenic variants in PLEKHG5 have been reported to date to be causative in three unrelated families with autosomal recessive intermediate Charcot-Marie-Tooth disease (CMT) and in one consanguineous family with spinal muscular atrophy (SMA). PLEKHG5 is known to be expressed in the human peripheral nervous system, and previous studies have shown its function in axon terminal autophagy of synaptic vesicles, lending support to its underlying pathogenetic mechanism. Despite this, there is limited knowledge of the clinical and genetic spectrum of disease. METHODS: We leverage the diagnostic utility of exome and genome sequencing and describe novel biallelic variants in PLEKHG5 in 13 individuals from nine unrelated families originating from four different countries. We compare our phenotypic and genotypic findings with a comprehensive review of cases previously described in the literature. RESULTS: We found that patients presented with variable disease severity at different ages of onset (8-25 years). In our cases, weakness usually started proximally, progressing distally, and can be associated with intermediate slow conduction velocities and minor clinical sensory involvement. We report three novel nonsense and four novel missense pathogenic variants associated with these PLEKHG5-associated neuropathies, which are phenotypically spinal muscular atrophy (SMA) or intermediate Charcot-Marie-Tooth disease. CONCLUSIONS: PLEKHG5-associated neuropathies should be considered as an important differential in non-5q SMAs even in the presence of mild sensory impairment and a candidate causative gene for a wide range of hereditary neuropathies. We present this series of cases to further the understanding of the phenotypic and molecular spectrum of PLEKHG5-associated diseases.

A homozygous UBA5 pathogenic variant causes a fatal congenital neuropathy.

BACKGROUND: UBA5 is the activating enzyme of UFM1 in the ufmylation post-translational modification system. Different neurological phenotypes have been associated with UBA5 pathogenic variants including epilepsy, intellectual disability, movement disorders and ataxia. METHODS AND RESULTS: We describe a large multigenerational consanguineous family presenting with a severe congenital neuropathy causing early death in infancy. Whole exome sequencing and linkage analysis identified a novel homozygous UBA5 NM_024818.3 c.31C>T (p.Arg11Trp) mutation. Protein expression assays in mouse tissue showed similar levels of UBA5 in peripheral nerves to the central nervous system. CRISPR-Cas9 edited HEK (human embrionic kidney) cells homozygous for the UBA5 p.Arg11Trp mutation showed reduced levels of UBA5 protein compared with the wild-type. The mutant p.Arg11Trp UBA5 protein shows reduced ability to activate UFM1. CONCLUSION: This report expands the phenotypical spectrum of UBA5 mutations to include fatal peripheral neuropathy.

Characterising the phenotype and mode of inheritance of patients with inherited peripheral neuropathies carrying MME mutations.

BACKGROUND: Mutations in the metalloendopeptidase (MME) gene were initially identified as a cause of autosomal recessive Charcot-Marie-Tooth disease type 2 (CMT2). Subsequently, variants in MME were linked to other late-onset autosomal dominant polyneuropathies. Thus, our goal was to define the phenotype and mode of inheritance of patients carrying changes in MME. METHODS: We screened 197 index cases with a hereditary neuropathy of the CMT type or distal hereditary motor neuropathy (dHMN) and 10 probands with familial amyotrophic lateral sclerosis (fALS) using a custom panel of 119 genes. In addition to the index case subjects, we also studied other clinically and/or genetically affected and unaffected family members. RESULTS: We found 17 variants in MME in a total of 20 index cases, with biallelic MME mutations detected in 13 cases from nine families (three in homozygosis and six in compound heterozygosis) and heterozygous variants found in 11 families. All patients with biallelic variants had a similar phenotype, consistent with late-onset axonal neuropathy. Conversely, the phenotype of patients carrying heterozygous mutations was highly variable [CMT type 1 (CMT1), CMT2, dHMN and fALS] and mutations did not segregate with the disease. CONCLUSION: MME mutations that segregate in an autosomal recessive pattern are associated with a late-onset CMT2 phenotype, yet we could not demonstrate that MME variants in heterozygosis cause neuropathy. Our data highlight the importance of establishing an accurate genetic diagnosis in patients carrying MME mutations, especially with a view to genetic counselling.

[Peripheral nerve involvement in rheumatic diseases]. / Periphere Nervenbeteiligung bei rheumatischen Erkrankungen.

Peripheral neuropathies are probably an under-diagnosed complication of many rheumatic diseases. In some cases they take a mild clinical course, in others they cause severe impairment of patients' quality of life. A precise diagnosis and etiological classification are of major importance for successful treatment and prognosis of peripheral neuropathies. A detailed patient history and physical examination are the foundation of every diagnostic approach. Electrophysiological studies are obligatory when peripheral neuropathy is suspected, whereas nerve or nerve-muscle biopsies are indicated only in selected cases. Therapeutic approaches are often complicated by a lack of evidence. They correspond to frequently tested immunosuppressive treatment of the underlying disease, such as glucocorticoids, cyclophosphamide, mycophenolate mofetil and intravenous immunoglobulins and are based on the symptomatic pain treatment of other neuropathies. As first-line treatment gabapentin, pregabalin, duloxetine, venlafaxine and tricyclic antidepressants are frequently used.

Paraspinal neurofibromas and hypertrophic neuropathy in Noonan syndrome with multiple lentigines.

BACKGROUND: Noonan syndrome with multiple lentigines (NSML), formerly known as LEOPARD syndrome, is an autosomal-dominant disorder characterised by lentigines, EKG abnormalities, ocular hypertelorism, pulmonic stenosis, abnormal genitalia, growth retardation and deafness. There is significant clinical overlap between NSML and other disorders that result from dysregulated rat sarcoma/mitogen-activated protein kinase pathway (RASopathies). Except for neurofibromatosis type 1, other RASopathies are not known to be typically associated with neurogenic tumours. METHODS AND RESULTS: We evaluated patients from three families with pigmentary skin lesions, progressive neuropathy, enlarged nerves, massive burden of paraspinal tumours (neurofibroma was confirmed in one patient) and a clinical diagnosis of NSML. All patients had a mutation in the protein tyrosine phosphatase catalytic domain of the PTPN11 gene; two unrelated patients had the p.Thr468Met mutation, while the family consisting of two affected individuals harboured the p.Thr279Cys mutation. Molecular analysis performed on hypertrophic nerve tissue did not disclose a second somatic hit in NF1, PTPN11, NF2 or SMARCB1 genes. CONCLUSIONS: Neurogenic tumours and hypertrophic neuropathy are unusual complications of NSML and may be an under-recognised manifestation that would warrant surveillance. Our observation may also have implications for other disorders caused by RAS-pathway dysregulation.

Charcot-Marie-Tooth diseases: an update and some new proposals for the classification.

BACKGROUND: Charcot-Marie-Tooth (CMT) disease, the most frequent form of inherited neuropathy, is a genetically heterogeneous group of disorders of the peripheral nervous system, but with a quite homogeneous clinical phenotype (progressive distal muscle weakness and atrophy, foot deformities, distal sensory loss and usually decreased tendon reflexes). Our aim was to review the various CMT subtypes identified at the present time. METHODS: We have analysed the medical literature and performed a historical retrospective of the main steps from the individualisation of the disease (at the end of the nineteenth century) to the recent knowledge about CMT. RESULTS: To date, >60 genes (expressed in Schwann cells and neurons) have been implicated in CMT and related syndromes. The recent advances in molecular genetic techniques (such as next-generation sequencing) are promising in CMT, but it is still useful to recognise some specific clinical or pathological signs that enable us to validate genetic results. In this review, we discuss the diagnostic approaches and the underlying molecular pathogenesis. CONCLUSIONS: We suggest a modification of the current classification and explain why such a change is needed.

Utility of next generation sequencing in genetic diagnosis of early onset neuromuscular disorders.

BACKGROUND: Neuromuscular disorders are a clinically, pathologically, and genetically heterogeneous group. Even for the experienced clinician, an accurate diagnosis is often challenging due to the complexity of these disorders. Here, we investigated the utility of next generation sequencing (NGS) in early diagnostic algorithms to improve the diagnosis for patients currently lacking precise molecular characterisation, particularly for hereditary myopathies. METHODS: 43 patients presenting with early onset neuromuscular disorders from unknown genetic origin were tested by NGS for 579 nuclear genes associated with myopathy. RESULTS: In 21 of the 43 patients, we identified the definite genetic causes (48.8%). Additionally, likely pathogenic variants were identified in seven cases and variants of uncertain significance (VUS) were suspected in four cases. In total, 19 novel and 15 known pathogenic variants in 17 genes were identified in 32 patients. Collagen VI related myopathy was the most prevalent type in our cohort. The utility of NGS was highlighted in three cases with congenital myasthenia syndrome, as early diagnosis is important for effective treatment. CONCLUSIONS: A targeted NGS can offer cost effective, safe and fairly rapid turnaround time, which can improve quality of care for patients with early onset myopathies and muscular dystrophies; in particular, collagen VI related myopathy and congenital myasthenia syndromes. Nevertheless, a substantial number of patients remained without molecular diagnosis in our cohort. This may be due to the intrinsic limitation of detection for some types of mutations by NGS or to the fact that other causative genes for neuromuscular disorders are yet to be identified.

Accuracy of MRI in diagnosing peripheral nerve disease: a systematic review of the literature.

OBJECTIVE: MRI is increasingly being used to evaluate extracranial peripheral nerve disease in clinical practice. The objective of this study was to systematically review the accuracy of MRI in distinguishing normal from abnormal extracranial peripheral nerves. CONCLUSION: There is significant heterogeneity between studies investigating the accuracy of MRI. Studies have shown that nerve T2-weighted or STIR hyperintensity, nerve enlargement, and nerve flattening are associated with peripheral nerve disease.

Genome-wide association study identifies ephrin type A receptors implicated in paclitaxel induced peripheral sensory neuropathy.

BACKGROUND: Peripheral neuropathy is the dose limiting toxicity of paclitaxel, a chemotherapeutic drug widely used to treat solid tumours. This toxicity exhibits great inter-individual variability of unknown origin. The present study aimed to identify genetic variants associated with paclitaxel induced neuropathy via a whole genome approach. METHODS: A genome-wide association study (GWAS) was performed in 144 white European patients uniformly treated with paclitaxel/carboplatin and for whom detailed data on neuropathy was available. Per allele single nucleotide polymorphism (SNP) associations were assessed by Cox regression, modelling the cumulative dose of paclitaxel up to the development of grade 2 sensory neuropathy. RESULTS: The strongest evidence of association was observed for the ephrin type A receptor 4 (EPHA4) locus (rs17348202, p=1.0×10(-6)), and EPHA6 and EPHA5 were among the top 25 and 50 hits (rs301927, p=3.4×10(-5) and rs1159057, p=6.8×10(-5)), respectively. A meta-analysis of EPHA5-rs7349683, the top marker for paclitaxel induced neuropathy in a previous GWAS (r(2)=0.79 with rs1159057), gave a hazard ratio (HR) estimate of 1.68 (p=1.4×10(-9)). Meta-analysis of the second hit of this GWAS, XKR4-rs4737264, gave a HR of 1.71 (p=3.1×10(-8)). Imputed SNPs at LIMK2 locus were also strongly associated with this toxicity (HR=2.78, p=2.0×10(-7)). CONCLUSIONS: This study provides independent support of EPHA5-rs7349683 and XKR4-rs4737264 as the first markers of risk of paclitaxel induced neuropathy. In addition, it suggests that other EPHA genes also involved in axonal guidance and repair following neural injury, as well as LIMK2 locus, may play an important role in the development of this toxicity. The identified SNPs could form the basis for individualised paclitaxel chemotherapy.

Severe papilloedema with vision loss secondary to Guillain-Barré syndrome.

We discuss a patient who presented with bilateral VI and VII cranial nerve palsies, symmetric upper and lower limb weakness and areflexia, 2 weeks following an flu-like illness. At presentation, there was no papilloedema, and her visual function was normal. Cerebrospinal fluid analysis and electrophysiology supported the diagnosis of Guillain-Barré Syndrome (GBS). She received intravenous immunoglobulins. She subsequently developed headaches and vision loss. Funduscopy demonstrated severe papilloedema with visual acuity of 6/18 right eye, 6/12 left eye with bitemporal visual field depression. Lumbar puncture revealed elevated opening pressure with high protein and normal cell count. She received acetazolamide. There was resolution of papilloedema and normal visual function at 3 months. Of note, the patient's body mass index was 17 kg/m2Our case highlights the rare occurrence of papilloedema in GBS, reiterating the importance of performing funduscopy on patients with any neurological diagnosis. Early detection and prompt management of papilloedema can prevent permanent vision loss.

Acute sensorimotor paraneoplastic neuropathy in a patient with small cell prostate cancer.

The authors describe a patient with a background of metastatic small cell prostate cancer who presented with a rapidly evolving sensorimotor neuropathy with bulbar features closely resembling Guillain-Barré syndrome, with a good initial response to intravenous immunoglobulins and platinum-based chemotherapy. This represented a likely paraneoplastic manifestation of the patient's urological malignancy.

Sweet syndrome with peripheral neuropathy in a patient with metastatic clear cell renal cell carcinoma.

A female patient in her 70s with a newly diagnosed clear cell renal cell carcinoma (ccRCC) with osseous metastasis presented with sudden onset erythematous painful blistering skin lesions on the dorsum of both hands, with associated intermittent fever episodes. Blood tests showed elevated inflammatory marker levels (C reactive protein 257.8 mg/dL, leucocytes 17.79×109/L, with 94% neutrophils). Histologically, there was predominately neutrophil dermal infiltrate without leucocytoclastic vasculitis. The diagnostic criteria of Sweet syndrome were fulfilled. A week later, the patient developed abrupt left-hand palsy, which was confirmed as a medial and ulnar sensorimotor axonal peripheral neuropathy of paraneoplastic origin. The patient was prescribed a course of oral high-dose steroids, which significantly improved the skin lesions. The peripheral nerve palsy improved after 3 months. This case describes the two very rare concurrent paraneoplastic manifestations of ccRCC occurring simultaneously, which have been rarely reported.

Deficiency of adenosine deaminase 2: a genetic autoinflammatory disorder mimicking childhood polyarteritis nodosa.

A girl in the early adolescent age group presented with multisystem manifestations in the form of periodic fever, recurrent abdominal pain, hypertension, seizure, skin lesions over the chest and gangrene over the left ring and middle fingertips. Her condition had remained undiagnosed for 11 years. On evaluation, she had features of polyarteritis nodosa (PAN) (multiple aneurysms, symmetric sensorimotor peripheral neuropathy, superficial ulcers, digital necrosis, myalgia, hypertension and proteinuria). As childhood PAN is a phenocopy of adenosine deaminase 2 with a different management strategy, whole-exome sequencing was performed, which revealed a pathogenic variant in ADA2 gene. The child was treated with TNF alpha inhibitors and showed improvement in the Paediatric Vasculitis Activity Score. The paper highlights the gratifying consequences of correct diagnosis with disease-specific therapy that ended the diagnostic odyssey, providing relief to the patient from debilitating symptoms and to the family from the financial burden of continued out-of-pocket health expenditure.

Concurrent transverse myelitis and acute inflammatory demyelinating polyneuropathy.

A woman in her 40s presented with thoracic banding dysaesthesia and lower motor neuron weakness. Spinal imaging revealed a short segment of transverse myelitis and neurophysiology was suggestive of concurrent acute inflammatory demyelinating polyneuropathy. The patient improved with consecutive intravenous immunoglobulin and methylprednisolone treatment. Acute inflammatory demyelinating polyneuropathy is a progressive immune-mediated peripheral neuropathy which responds to intravenous immunoglobulin or plasmapheresis, whereas transverse myelitis is a central inflammatory syndrome usually treated with corticosteroid. We highlight differentiating features of the clinical presentation and the utility of investigations such as neurophysiology and MRI along with a review of treatment and the role for corticosteroid therapy.

Guillain-Barré syndrome following primary cytomegalovirus infection in a patient with liver transplantation.

We present the case of a man in his 60s with a 5-month medical history of deceased donor liver transplantation, who developed Guillain-Barré syndrome (GBS) secondary to a primary cytomegalovirus (CMV) infection. This was confirmed by molecular tests and serology antibodies that ruled out other frequent aetiologies. Therapy with intravenous immunoglobulin and valganciclovir was started and the patient gradually improved over the weeks. GBS is the most common aetiology of paralysis worldwide, and it is an autoimmune-mediated neuropathy that is frequently caused by a preceding infection. Few cases of GBS have been reported in the context of liver transplant recipients, and those related to CMV infection are extremely rare. This case highlights the importance of considering GBS as a possible differential diagnosis in patients with solid organ transplantation, and it contributes to the knowledge of other infrequent aetiologies of this condition.

The role of imaging in focal neuropathies.

Electrodiagnostic testing (EDX) has been the diagnostic tool of choice in peripheral nerve disease for many years, but in recent years, peripheral nerve imaging has been used ever more frequently in daily clinical practice. Nerve ultrasound and magnetic resonance (MR) neurography are able to visualize nerve structures reliably. These techniques can aid in localizing nerve pathology and can reveal significant anatomical abnormalities underlying nerve pathology that may have been otherwise undetected by EDX. As such, nerve ultrasound and MR neurography can significantly improve diagnostic accuracy and can have a significant effect on treatment strategy. In this chapter, the basic principles and recent developments of these techniques will be discussed, as well as their potential application in several types of peripheral nerve disease, such as carpal tunnel syndrome (CTS), ulnar neuropathy at the elbow (UNE), radial neuropathy, brachial and lumbosacral plexopathy, neuralgic amyotrophy (NA), fibular, tibial, sciatic, femoral neuropathy, meralgia paresthetica, peripheral nerve trauma, tumors, and inflammatory neuropathies.

Treatment-induced neuropathy of diabetes: challenges in diagnosing neuropathic pain, value of sudomotor function testing.

A patient in his 60s was admitted for an extensive neurological work-up due to progressive asymmetrical, distally pronounced pain in both feet and legs. Conventional pain relievers did not help in pain reduction. A Sudoscan revealed small fibre damage in all extremities indicating an underlying neuropathy. The patient had started insulin treatment around 6 months prior to hospitalisation because of a newly diagnosed late-onset diabetes. Due to a rapid drop in glycated haemoglobin (from over 14% to 6% in 4 months), treatment-induced neuropathy of diabetes (TIND) was hypothesised. On increasing the dose of pregabalin and adding duloxetine, the patient reported improvement of symptoms, which further underlined the suspected diagnosis. Hence, in patients with severe hyperglycaemia, changes in glycaemic control should be stepwise and not rapid; however, to date, no guidelines exist how to avoid TIND.

Epithelioid malignant peripheral nerve sheath tumour of the ulnar nerve around the elbow: a diagnostic and therapeutic challenge.

Epithelioid malignant peripheral nerve sheath tumour (EMPNST) is a rare histological subtype of malignant peripheral nerve sheath tumour (MPNST), accounting for 5% to 17% of MPNSTs. The clinical and MRI findings of EMPNST mimic those of nerve abscesses, similar to the presentation in Hansen's disease. We present one such case with this kind of diagnostic dilemma. Intraoperative findings suggest a tumour changed the course of management subsequently. The development of neurological deficits postoperatively after tumour resection was a reconstructive challenge. To provide motor power and sensation through a procedure that provides a complete functional outcome for a young patient, distal nerve transfers were chosen. This provided an improvement in the quality of life and hastened the neurological recovery of the involved limb. Level of evidence: V.

Chronic inflammatory demyelinating polyneuropathy caused by hepatocellular carcinoma.

Paraneoplastic syndromes are rare abnormal endocrine or immune responses triggered by neoplasms. Chronic inflammatory demyelinating polyneuropathy (CIDP) is one such example. CIDP is an acquired, immune-mediated neuropathy affecting the peripheral nerves and nerve roots. It is associated with many types of cancers, especially haematological malignancies. We report the case of a man in his 60s who presented to the emergency department with acute symptoms of upper and lower extremity paresis and decreased sensation in the toes and tips of his fingers. Laboratory tests were normal. Electrodiagnostic studies showed diffuse motor and sensory dysfunction in all extremities; a diagnosis of CIDP was consequently made. Imaging studies showed a large left lobe liver mass. Subsequent biopsy revealed histopathological findings characteristic of hepatocellular carcinoma. After failure of medical treatment with intravenous immunoglobulin and corticosteroids, laparoscopic resection of the tumour was planned, performed and resulted in complete resolution of symptoms. At 18 months postoperatively, the patient was asymptomatic.

Rare case of anti-CV2 paraneoplastic polyneuropathy associated with lung adenocarcinoma.

We describe the first case of anti-CV2 paraneoplastic polyneuropathy associated with lung adenocarcinoma. Our patient presented with progressive unsteadiness and numbness involving bilateral upper and lower limbs. He had symmetrical length-dependent lower motor neuron pattern of weakness and numbness involving both small and large fibres with prominent sensory ataxia. An extended workup for the polyneuropathy involving a serum paraneoplastic antineuronal antibody panel showed a positive reaction for anti-CV2 antibody. CT scan of the thorax, abdomen and pelvis revealed a right upper lung nodule and histopathological examination of the nodule revealed lung adenocarcinoma. He was scheduled for chemotherapy following his discharge and there was improvement of his sensorimotor polyneuropathy following his chemotherapy.