Background The homozygosity for CAG expansion is a very rare finding in HD patients. It is assumed, that homozygous cases show similar age at onset in comparison to the heterozygotes with the same expansion length but the disease progression seems to be more rapid with pronounced psychiatric symptoms, probably due to wider neuronal degeneration. We present the clinical course of two HD patients harbouring two mutant alleles, diagnosed in the Institute of Psychiatry and Neurology (IPN), Warsaw, Poland.
Case history Two patients were clinically and genetically evaluated while being enrolled into the REGISTRY EHDN project. They showed different clinical presentation and course of the disease.
The first subject (28 y.o.) with 38 and 63 CAG repeats presented with juvenile HD phenotype. Symptoms began at age of 12, with rapid development of dystonia and rigidity (Baseline TMS 74), the presence of epileptic seizures, cognitive impairment, severe irritability and obsessive-compulsive disorder.
The second patient (44 y.o.) with 40 and 42 CAG repeats showed first symptoms at the age of 40. Until now the patient is affected with a mild motor symptoms (TMS 23). The depression with suicidal ideations and psychotic symptoms (delusions) seem to be the most important clinical problem. The rate of decline of cognitive abilities is not different from these observed in heterozygous patients.
Conclusions Our study on two homozygous HD cases revealed, that the clinical course of motor symptoms in them does not differ significantly from the relevant cohorts of heterozygotic subjects. However, it confirmed suggestions from other reports that the psychiatric component of HD clinical presentation may be more severe in homozygous subjects.
- CAG mutation homozygosity
- CAG expansion
- psychiatric symptoms