Familial Dysautonomia with Anhydrosis (Type IV)
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Familial dysautonomia with anhidrosis type IV is a very rare cause of anhidrosis. It has an autosomal recessive inheritance. The diagnosis is suspected clinically in patients who present with anhidrosis and repetitive trauma; however, a histamine flare test can be performed. These patients will not produce a flare . Once clinically suspected, genetic testing can confirms an abnormal NTRK1 (TRKA) gene, located on chromosome 1 . This gene encodes for a neurotropic tyrosine kinase receptor type 1, which plays an important role in the nerve growth factor pathway ultimately leading to the failure to thrive of unmyelinated fibers and some small myelinated fibers .