The Wolfram syndrome (WFS, OMIM 222300) is a rare genetic disease with a prevalence of cca 1:710 000 .The disease is also known as the DIDMOAD syndrome (Diabetes Insipidus, early-onset Diabetes Mellitus, progressive Optic Atrophy and Deafness). Most of the individuals afflicted by this disease have the recessive mutation in the Wolfram syndrome gene 1 (WFS1, 4p16.3), rarely in the Wolfram syndrome gene 2 (WFS2). What is more, a dominant mutation in the WFS1 gene was described in connection with sensorineural hearing loss, deafness and optic atrophy: Wolfram-like syndrome, WFSL. At present the disease ranks among the so-called the endoplasmic reticulum diseases. In the past many times loss of function mutations were described in WFS1 patients but in some patients there was no mutation in the WFS1. Variable clinical symptoms, rare occurrence and molecular complexity complicate diagnosis and the genotype-phenotype correlation of the disease. Survival of the afflicted individuals is shortened also due to other handicaps, such as respiratory failure, aspiration of food, neurological problems (brain atrophy, nystagmus, dysarthria, motor clumsiness, vertigo, spastic paraplegia, mental handicap), psychiatric symptoms (depression, suicidal tendencies, self-destructive behaviour, ADHD), sensorineural deafness, disorders of kidneys and the urinary tract.