Orthostatic Intolerance

A number sign (#) is used with this entry because of evidence that orthostatic intolerance is caused by heterozygous mutation in the gene encoding the norepinephrine transporter (SLC6A2; 163970) on chromosome 16q12. One such family has been reported.

Clinical Features

Orthostatic intolerance is a syndrome characterized by adrenergic symptoms that occur when an upright posture is assumed: the heart rate increases by at least 30 beats per minute, without orthostatic hypotension (Jacob et al., 1997). Most patients with orthostatic intolerance are women between the ages of 20 and 50 years (Low et al., 1995). This syndrome, first described by Da Costa (1871), has been called soldiers heart (Fraser and Wilson, 1918), neurocirculatory asthenia (Wooley, 1976), and mitral valve prolapse syndrome (Boudoulas et al., 1980). It is similar in many respects to chronic fatigue syndrome (Schondorf and Freeman, 1999).

Molecular Genetics

In a family with orthostatic intolerance, Shannon et al. (2000) identified heterozygosity for a mutation in the SLC6A2 gene (163970.0001).