The straight back syndrome.

The straight back syndrome, consisting of loss of normal upper thoracic spinal curvature associated with cardiac murmurs and radiographic cardiomegaly is considered a form of 'pseudoheart disease' which has been attributed to squashing of the heart in the reduced AP diameter of the chest. During an 18-month period 31 patients referred to a cardiologist were found to have a straight back. Forty-five relatives were subsequently examined and 27 were found also to have a straight back. Palpitations and chest pain were the commonest symptoms. On the lateral chest radiograph the distance from the middle of the anterior border T8 to a vertical line connecting T4 and T12 was found to be significantly reduced compared to controls, and a value less 1.2 cm is indicative of a straight back. Of the 58 subjects with the syndrome, 39 (67 per cent) had clinical and/or echocardiographic evidence of mitral valve prolapse. Respiratory function testing revealed no significant abnormality. HLA typing showed no association with an particular HLA antigen but indicates that the straight back syndrome is inherited as an autosomal dominant condition and suggested that the antigenic determinants may be located on chromosome 6. We conclude that the straight back syndrome should no longer be considered a form of pseudoheart disease and patients should be investigated for associated mitral valve prolapse and their relatives screened.