Huntington's disease and Huntington's disease-like syndromes: an overview.

PURPOSE OF REVIEW

The differential diagnosis of chorea syndromes may be complex and includes various genetic disorders such as Huntington's disease and mimicking disorders called Huntington's disease-like (HDL) phenotypes. To familiarize clinicians with these (in some cases very rare) conditions we will summarize the main characteristics.

RECENT FINDINGS

HDL disorders are rare and account for about 1% of cases presenting with a Huntington's disease phenotype. They share overlapping clinical features, so making the diagnosis purely on clinical grounds may be challenging, however presence of certain characteristics may be a clue (e.g. prominent orofacial involvement in neuroferritinopathy etc.), Information of ethnic descent will also guide genetic work-up [HDL2 in Black Africans; dentatorubral-pallidoluysian atrophy (DRPLA) in Japanese etc.], Huntington's disease, the classical HDL disorders (except HDL3) and DRPLA are repeat disorders with anticipation effect and age-dependent phenotype in some, but genetic underpinnings may be more complicated in the other chorea syndromes.

SUMMARY

With advances in genetics more and more rare diseases are disentangled, allowing molecular diagnoses in a growing number of choreic patients. Hopefully, with better understanding of their pathophysiology we are moving towards mechanistic therapies.