Neuroakanthozytose-Syndrome
Neuroacanthocytosis Syndromes
The rare conditions collectively labelled as neuroacanthocytosis (NA) seriously disable young adults and place a heavy burden on them and their families. NA syndromes affect about 1 in 3 million individuals and present a variety of emotional, cognitive and movement disorders. They share considerable similarities with Huntington´s disease (HD). As in HD, the basal ganglia are preferentially affected by neurodegeneration but in contrast to HD a key to the understanding of underlying mechanisms may be found in easily accessible peripheral cells.
It is characteristic for NA that deformed erythrocytes with thorny protrusions are found in the patients´ blood. Although not detectable in every single case, these cells are the origin of the term neuroacanthocytosis, denoting the association of neurological findings and acanthocytes (“akantha”: Greek for thorn).
NA syndromes may be divided into those with lipid abnormalities and peripheral nervous system involvement (such as abetalipoproteinemia) and into the “core” NA syndromes with central nervous system involvement, including basal ganglia degeneration. Currently, the genetic basis is known for four of these conditions: McLeod syndrome (MLS, X-linked), chorea-acanthocytosis (ChAc, autosomal recessive), Huntington´s disease-like 2 (HDL2, autosomal dominant) and pantothenate kinase associated neurodegeneration (PKAN, autosomal recessive). Responsible genes are the Kell protein associated XK in MLS, VPS13A (vacuolar protein sorting 13 A, chorein) in ChAc, JPH3 (junctophilin 3) in HDL2 and PANK2 (pantothenate kinase 2) in PKAN. The recognition of PKAN as part of the NA spectrum creates a link to the NBIA group of syndromes (“neurodegeneration with brain iron accumulation”). NBIA syndromes are characterized by high brain iron with typical magnetic resonance imaging findings and the presence of axonal spheroids on histology. NBIA syndromes include some genetically still undefined conditions: PLA2G mutations were most recently added to the list of genes involved. At least 8% of PKAN patients show RBC acanthocytosis yet for other NBIA syndromes such analyses are currently not available
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