One novel GRN null mutation, two different aphasia phenotypes

A novel GRN mutation in an Italian patient with non-fluent variant of primary progressive aphasia at onset: a longitudinal case report

Objectives

We report the clinical presentation and evolution of a case with a novel Progranulin gene (GRN) mutation and non-fluent language disturbances at onset.

Materials and methods

A 60 year-old, white patient was followed due to a history of language disturbances. Eighteen months after onset, the patient underwent FDG positron emission tomography (PET), and at month 24 was hospitalized to perform neuropsychological evaluation, brain 3 T MRI, lumbar puncture for cerebrospinal fluid (CSF) analysis, and genotyping. At month 31, the patient repeated the neuropsychological evaluation and brain MRI.

Results

At onset the patient complained prominent language production difficulties, such as effortful speech and anomia. At month 18, FDG-PET showed left fronto-temporal and striatal hypometabolism. At month 24, the neuropsychological evaluation reported prevalent speech and comprehension deficits. Brain MRI reported left fronto-opercular and striatal atrophy, and left frontal periventricular white matter hyperintensities (WMHs). Increased CSF total tau level was observed. Genotyping revealed a new GRN c.1018delC (p.H340TfsX21) mutation. The patient received a diagnosis of non-fluent variant of primary progressive aphasia (nfvPPA). At month 31, language deficits worsened, together with attention and executive functions. The patient presented also with behavioral disturbances, and a progressive atrophy in the left frontal-opercular and temporo-mesial region.

Discussion and conclusion

The new GRN p.H340TfsX21 mutation resulted in a case of nfvPPA characterized by fronto-temporal and striatal alterations, typical frontal asymmetric WMHs, and a fast progression toward a widespread cognitive and behavioral impairment, which reflects a frontotemporal lobar degeneration. Our findings extend the current knowledge of the phenotypic heterogeneity among GRN mutation carriers.

FTD-PSP is an Unusual Clinical Phenotype in A Frontotemporal Dementia Patient with A Novel Progranulin Mutation

Progranulin (GRN) mutations are a major cause of frontotemporal dementia (FTD); the spectrum of clinical phenotypes of FTD is much more extensive than previously reported. The frequency and locations of GRN mutations in Chinese patients with FTD remain uncertain. We performed cDNA sequencing in one sporadic male patient who initially presented FTD symptoms. Brain magnetic resonance imaging (MRI) and positron emission computed tomography/computed tomography (PET/CT) were applied to further confirm the diagnosis of FTD from this patient. Cellular apoptosis and survival test were performed to identify the function of GRN. We identified one novel missense GRN mutation (c.1498G>A, p.V500I) in this patient, who initially presented typical behavioral-variant frontotemporal dementia (bvFTD) features but then presented progressive supranuclear palsy (PSP) clinical characteristics 5 years after onset. Besides, WT GRN protein showed an adequate trophic stimulus to preserve the survival of SH-SY5Y cells in the medium free of serum, while GRN mutation (c.1498G>A, p.V500I) may impair the ability of supporting cell survival. This study owns significant implications for genetic counseling and clinical heterogeneity. We illustrate the fact that FTD presenting features of bvFTD and PSP in one patient could be considered as a specific phenotype in patients with GRN mutations. GRN p.V500I led to the neuronal degeneration in vitro; this finding provides a significant evidence that this mutation may be a new causative mutation in patients with FTD.

Nosology of Primary Progressive Aphasia and the Neuropathology of Language

Primary progressive aphasia (PPA) is a dementia syndrome associated with several neuropathologic entities, including Alzheimer's disease (AD) and all major forms of frontotemporal lobar degeneration (FTLD). It is classified into subtypes defined by the nature of the language domain that is most impaired. The asymmetric neurodegeneration of the hemisphere dominant for language (usually left) is one consistent feature of all PPA variants. This feature offers unique opportunities for exploring mechanisms of selective vulnerability in neurodegenerative diseases and the neuroanatomy of language. This chapter reviews some of the current trends in PPA research as well as the challenges that remain to be addressed on the nosology, clinicopathologic correlations, and therapy of this syndrome.

The Rise of the GRN C157KfsX97 Mutation in Southern Italy: Going Back to the Fall of the Western Roman Empire

BACKGROUND

Frontotemporal lobar degeneration (FTLD) designates a group of neurodegenerative diseases with remarkable clinical, pathological, and genetic heterogeneity. Mutations in progranulin gene (GRN) are among the most common causes of familial FTLD. The GRN C157KfsX97 mutation is the most frequent mutation occurring in Southern Italy and has been already described in a previous work.

OBJECTIVE

In this study, we reported on additional cases carrying the same mutation and performed a genetic study on the whole cohort, aiming at demonstrating the existence of a founder effect and estimating the age of this mutation.

METHODS/RESULTS

Based on the haplotype sharing analysis, a founder effect was highly probable, while the age of the mutation, estimated by means of DMLE+ software, resulted in a range between 52 and 82 generations, with the highest frequency at about 62 generations, 1,550 years ago.

CONCLUSION

This is the first study that reports the age estimation of the most recent common ancestor for the GRN C157KfsX97 mutation recurring in Southern Italy. Mutation dating in a geographically restricted population may be useful in order to plan genetic counseling and screening programs in the field of public health.