Dementia of frontal lobe type in Kennedy's disease.

The pathomorphological correlate of Kennedy's disease (KD) is a degeneration of spinal and bulbar alpha-motor neurons. The disease is caused by a CAG repeat expansion in the first exon of the X-chromosomal androgene receptor gene. Contrary to the common belief that cognitive disorders in motor neuron diseases (MND) are either rare or only mild, there is now an increasing number of case reports on dementia in amyotrophic lateral sclerosis (ALS). In ALS, dementia of the frontal lobe type (frontotemporal dementia, FTD) seems to be the characteristic pattern. However, in KD cognitive dysfunction has not been studied systematically. Here we present a case with clinical characteristics of FTD in a patient with genetically confirmed KD. It remains speculative whether there is an association between KD and FTD comparable to a genetic linkage between ALS and FTD, which has been proposed in recent years. However, we suggest that cognitive dysfunction may be more common in KD than reported until today.