A novel homozygous mutation in TREM2 found in a Chinese early-onset dementia family with mild bone involvement.

Variants in triggering receptor expressed on myeloid cells 2 (TREM2) are associated with both behavioral variant frontotemporal lobar degeneration and Alzheimer's disease. TREM2 homozygous mutations cause Nasu-Hakola disease, an early-onset recessive form of dementia preceded by bone cysts and fractures. The same type of mutations has been shown to cause frontotemporal dementia without the presence of any bone phenotype. Herein, we report a Chinese Han consanguineous family carrying a novel TREM2 mutation, presenting with early-onset dementia similar to behavioral variant frontotemporal dementia with mild radiological bone involvement. Minigene reporter assay showed the variant disturbed splicing by preservation of intron 2 in transcription. In our investigation, the clinical and genetic spectra of Chinese early-onset dementia patients were expanded; TREM2 mutations should be screened in familial and Chinese early-onset dementia patients.