What is it?
Kearns-Sayre syndrome was first described in 1958 by Dr Thomas Kearns and Dr George Sayre.
The condition (sometimes called oculocraniosomatic disease) occurs because of large-scale single deletions or rearrangements of mitochondrial DNA. These are not usually inherited but occur spontaneously, probably at the germ-cell level or early in embryonic development. The risk of maternal transmission is about one in 24.
Signs and symptoms?
Kearns-Sayre syndrome is characterised by the onset of ophthalmoparesis, ptosis and pigmentary retinopathy before age 20 years. It may be associated with cerebellar ataxia, heart block, raised CSF protein and proximal myopathy.
Affected children have short stature and may have multiple endocrinopathies including diabetes mellitus, hypoparathyroidism and Addison's disease. Renal tubular acidosis can lead to renal failure, and bilateral sensorineural hearing loss invariably develops as patients age. There are no predilections regarding race or sex.
What are the mortality and morbidity figures?
Kearns-Sayre syndrome is a slowly progressive disorder that reduces life expectancy, but specific figures are not available. Prognosis depends on the severity and number of organs involved. Early diagnosis and ECG monitoring are vital because heart block is an important cause of death that is preventable by early pacemaker implantation.
How is it diagnosed?
There is no simple specific test, but in young children, single large-scale deletions may be detectable in blood cell samples. Muscle biopsy may show ragged red fibres with mitochondrial proliferation, degeneration and vacuolation. Muscle histochemistry shows a deficiency of cytochrome oxidase.
Patients should be screened for endocrine abnormalities.
Brain MRI may show subcortical white matter lesions with involvement of the thalamus, basal ganglia and brainstem. Cerebral and cerebellar atrophy may be present. ECG will reveal conduction defects and echocardiography may demonstrate cardiomyopathy.
Electroretinography, audiometry, electroencephalography, electromyography and nerve conduction studies can help determine the degree of multi-organ involvement.
What is the treatment?
There no way of correcting the mitochondrial abnormalities, so treatment is symptomatic and supportive.
A multidisciplinary team should be involved including cardiology, audiology, ophthalmology, endocrinology, neurology and neuropsychiatry. The limitations of eye movement are not amenable to treatment. Endocrine abnormalities can be treated with medications.
Exercise may help patients with myopathy. The use of cochlear implants for patients with significant deafness is under investigation.
- Dr Barnard is a former GP from Fareham, Hampshire