SNP Shot: Genomic Insights

Dementia with Lewy bodies (DLB) is a brain disease that affects thinking skills (dementia) and causes movement problems similar to Parkinson's disease (parkinsonism). Key features include vivid visual hallucinations, unpredictable changes in alertness and thinking, and acting out dreams related to REM sleep behavior disorder (RBD). It usually starts in older adults, between ages 50 and 85. On average, people with DLB live for about 5 to 7 years after they are diagnosed.

RBD can be one of the first signs of DLB, sometimes appearing many years before other symptoms. With RBD, people physically act out their dreams, moving and talking in their sleep. As DLB gets worse and other symptoms show up, RBD may become less noticeable.

Dementia is often the second major symptom to appear in DLB. Cognitive decline can start subtly or change from day to day. The dementia linked to DLB often impacts visual-spatial abilities, such as putting puzzles together. People might also have trouble with problem-solving (executive function), speech difficulties, and poor impulse control. Memory issues usually develop later in the disease.

Seeing things that aren't there (visual hallucinations) is common in DLB, often involving images of people or animals. Fluctuations in cognitive abilities and behavior are also typical, including sudden shifts in attention, confused speech, and brief episodes of reduced awareness that may look like staring spells.

Parkinsonism, with symptoms like shaking (tremors), stiff muscles (rigidity), slow movement (bradykinesia), and balance problems (postural instability), is usually the last major symptom to emerge in DLB, but it can sometimes occur earlier. Eventually, individuals may need walking aids or a wheelchair.

Besides the main symptoms, people with DLB might also experience a significant drop in blood pressure when standing up (orthostatic hypotension), fainting (syncope), a reduced sense of smell, more saliva and drooling, trouble controlling their bladder (incontinence), or constipation.

Inheritance:

If DLB is caused by changes (mutations) in the SNCA or SNCB genes, it's inherited in an autosomal dominant way. This means that only one copy of the changed gene in each cell is enough to cause the disease. In these situations, a person with DLB usually has a parent who also has it. Having one copy of a variant in the GBA gene or the APOE e4 allele increases the chance of developing DLB, but doesn't guarantee it. Some individuals with these genetic variations never develop DLB. This increased risk is also inherited in an autosomal dominant manner.