TREM2 Variants as A Possible Cause of Frontotemporal Dementia with Distinct Neuroimaging Features.

Samanci, Bedia; Bilgiç, Başar; Gelişin, Özlem; Tepgeç, Fatih; Guven, Gamze; Tüfekçioğlu, Zeynep; Alaylıoğlu, Merve; Hanagasi, Hasmet A; Gürvit, Hakan; Guerreiro, Rita; Hardy, John; Emre, Murat

BACKGROUND Nasu-Hakola disease (NHD) is a rare, autosomal recessive disorder characterized by skeletal and neurological symptoms. Behavioral symptoms with cognitive impairment may mimic the behavioral variant of frontotemporal dementia (bvFTD) and other early-onset dementias. We analyzed our patients and reviewed the literature to delineate neurological and neuroimaging findings suggestive of NHD. METHOD Fourteen patients carrying a pathogenic mutation in the TREM2 gene were found in our database. Demographic, clinical, laboratory, radiological data were retrieved and analyzed. RESULTS Presenting clinical picture was behavioral changes with cognitive decline resembling bvFTD in all patients. The mean age was 37.1±4.97 years, the mean duration of the disease was 8.9±3.51 years. Only two patients had typical bone cysts. Seven patients had bilateral calcification of the basal ganglia in the computerized tomography of the brain. Magnetic resonance imaging (MRI) of the brain revealed severe atrophy of the corpus callosum, enlargement of the ventricles, atrophy of the caudate nuclei, periventricular white matter changes in all patients. Symmetrical global atrophy of the brain, mainly affecting frontoparietal and lateral temporal regions were observed in all cases, and 13 patients had atrophy of hippocampus. Cerebrospinal fluid examination of ten patients showed elevated protein levels in six and the presence of oligoclonal bands in four patients. CONCLUSION A combination of white matter changes, enlarged ventricles, atrophy of caudate nuclei, thinning of the corpus callosum in MRI strongly suggests NHD in patients with FTD syndrome. Molecular genetic analysis should be performed in suspected cases, and families should receive genetic counseling.