Multifocal motor neuropathy in Austria: a nationwide survey of clinical features and response to treatment.

BACKGROUND AND OBJECTIVES: Multifocal motor neuropathy (MMN) is a rare neuropathy and detailed descriptions of larger patient cohorts are scarce. The objective of this study was to evaluate epidemiological, clinical, and laboratory features of MMN patients and their response to treatment in Austria and to compare these data with those from the literature. METHODS: Anonymized demographic and clinical data about MMN patients until 31.12.2017 were collected from registered Austrian neurologists. Exploratory statistics on clinical and laboratory features as well as treatment regimens and responses were performed. RESULTS: 57 Patients with MMN were identified, resulting in a prevalence of 0.65/100.000. Mean age of onset was 44.1 ± 13.1 years, the diagnostic delay 5.5 ± 8.4 years. In 77% of patients, symptom onset was in the upper limbs, and in 92%, it occurred in distal muscles. Proximal onset was never observed in the lower limbs. At the final follow-up, the majority of patients had atrophy (88%) in affected regions. Definite motor conduction blocks (CB) were found in 54 patients. Anti-GM1-IgM antibodies were present in 43%. Treatment with intravenous immunoglobulins improved muscle strength and INCAT score initially, but at last follow-up, both scores deteriorated to values before treatment. DISCUSSION: The findings of the present study corroborate the previous findings in MMN. Onset typically occurs in the upper limbs and mostly distal, CBs are found in the majority of cases, while anti-GM1-IgM antibodies are detected in only approximately 40%. Our study underlines that the initial good response to treatment fades over time.

Whole-exome sequencing in patients with inherited neuropathies: outcome and challenges.

Inherited peripheral neuropathies (IPN) are one of the most frequent inherited causes of neurological disability characterized by considerable phenotypic and genetic heterogeneity. Based on clinical and electrophysiological properties, they can be subdivided into three main groups: HMSN, dHMN, and HSN. At present, more than 50 IPN genes have been identified. Still, many patients and families with IPN have not yet received a molecular genetic diagnosis because clinical genetic testing usually only covers a subset of IPN genes. Moreover, a considerable proportion of IPN genes has to be identified. Here we present results of WES in 27 IPN patients excluded for mutations in many known IPN genes. Eight of the patients received a definite diagnosis. While six of these patients carried bona fide pathogenic mutations in known IPN genes, two patients had mutations in genes known to be involved in other types of neuromuscular disorders. A further group of eight patients carried sequence variations in IPN genes that could not unequivocally be classified as pathogenic. In addition, combining data of WES and linkage analysis identified SH3BP4, ITPR3, and KLHL13 as novel IPN candidate genes. Moreover, there was evidence that particular mutations in PEX12, a gene known to cause Zellweger syndrome, could also lead to an IPN phenotype. We show that WES is a useful tool for diagnosing IPN and we suggest an expanded phenotypic spectrum of some genes involved in other neuromuscular and neurodegenerative disorders. Nevertheless, interpretation of variants in known and potential novel disease genes has remained challenging.