[The most common dysautonomias]

To review the classification and the clinical and pathological characteristics of the most common dysautonomias.

Primary dysautonomia includes neurodegenerative diseases of unknown causes that are characterised by the intracytoplasmic accumulations of alpha synuclein that manifest with four different phenotypes: pure autonomic failure, Parkinson s disease, dementia with Lewy bodies and multiple system atrophy. Of the secondary dysautonomias, diabetes mellitus is the most common cause of autonomic neuropathy in developed countries. Familiar dysautonomia is a recessive autosomic disease; the gene responsible for it has been located in the long arm of chromosome 9 (9q31). Paraneoplasic dysautonomia is associated with cancer of the lungs, the pancreas, Hodgkin's disease and testicular cancer. In Lambert Eaton myasthenic syndrome and in botulism the release of acetylcholine is deficient in both the somatic and the autonomic neurons. There are other diseases that affect autonomic cholinergic neurotransmission without bringing about any disorders in neuromuscular transmission. Chagas disease affects the neurons of the parasympathetic ganglion and produces megaesophagus, megacolon and myocardiopathy. Dopamine beta hydroxylase enzyme deficiency is a congenital disease characterised by the failure to convert dopamine into noradrenaline which results in orthostatic hypotension.

Dysautonomias can be classified, according to their aetiology, as primary or secondary; according to the deficient neurotransmitter, as cholinergic, adrenergic and mixed (pan dysautonomia) or, according to the anatomical distribution of the neurons that are affected, as central and peripheral.