[1] It is caused by autosomal recessive loss of function mutations in either the TREM2 or TYROBP gene that are found most frequently in the Finnish and Japanese populations.
The third stage (early neurological) is marked by the onset of symptoms typical of a frontal lobe syndrome (euphoria, lack of concentration, loss of judgment and social inhibitions) with memory loss.
[citation needed] This condition has been associated with mutations in the TYRO protein tyrosine kinase binding protein (TYROBP) gene and in the triggering receptor expressed on myeloid cells 2 (TREM2) gene.
[citation needed] X rays show the presence of bone cysts and osteoporosis.
EEG is typically normal initially but diffuse slowing and irritative activity later.