[Diagnosis and misdiagnosis in familial dysautonomia]

The method of diagnosis in 122 patients with familial dysautonomia (FD) was reviewed. In all cases the diagnosis was based on the clinical history, physical examination and results of the histamine test (concentrations of 1:1,000 and 1:10,000). In 8 patients the diagnosis was also supported by a meiotic response to pilocarpine (0.0625 mg/dl). 69 (56%) were diagnosed in the first year of life (19 of them relatives of known FD patients), 16 (13%) in the second year, 31 (25%) from 25 months to 10 years, 3 (2%) from 10.1-20 years, and 3 from 20.1-44 years. At diagnosis the mean age was 2.9 years (SD 5.84) and the median age 11 months. In 17 diagnosis was delayed by an average of 18.5 months (SD 16.9) from the time FD was initially suspected, mainly because of false interpretation of the histamine test. Early correct diagnosis is essential to prevent unnecessary morbidity and mortality from FD.