Information on the following diseases can be found in the Related Disorders section of this report:

• MELAS Syndrome
• MERRF Syndrome
• Leigh's Disease
• Pearson Marrow-Pancreas Syndrome

The three primary findings in Kearns-Sayre Syndrome are progressive paralysis of certain eye muscles (chronic progressive external ophthalmoplegia [CPEO]); abnormal accumulation of colored (pigmented) material on the nerve-rich membrane lining the eyes (atypical retinitis pigmentosa), leading to chronic inflammation, progressive degeneration, and wearing away of certain eye structures (pigmentary degeneration of the retina); and heart disease (cardiomyopathy) such as heart block. Symptoms of this disorder are usually apparent before the age of 20 years.

In most cases, the first physical characteristic of this disorder is retardation of growth. In addition, drooping of the upper eyelid (ptosis) due to weakness of one of the muscles of the eyelid (levator palpebrae superioris) is also seen early during infancy. Other muscles involved in coordinating eye movements may be affected next, growing progressively weaker and eventually resulting in paralysis of certain eye movements (chronic progressive external ophthalmoplegia [CPEO]). Eventually, muscle weakness may extend to other portions of the face, throat (pharynx), neck, and/or shoulders. Muscle weakness in such areas may hinder talking and/or swallowing (dysphagia). As the disease progresses, the upper arms and legs may be affected, resulting in progressive impairment of coordinated movement (ataxia) and/or a staggered or halting gait (titubation).

Most individuals with Kearns-Sayre Syndrome will also have visual difficulties due to the abnormal accumulation of colored (pigmented) material on the delicate membrane that lines the eyes (atypical retinitis pigmentosa) and progressive degeneration of certain portions of the eye (pigmentary degeneration of the retina). This degenerative process may eventually affect the optic nerve (optic atrophy), the layers of membranes behind the retina (choroid), and/or the tough, white outer covering of the eyeball (sclera). In some cases, affected individuals may also experience night blindness; rapid, involuntary eye movements (nystagmus); and a decrease in the sharpness of vision (visual acuity). In rare cases, abnormal clouding of the front portion of the eyeball (cornea) may also contribute to nystagmus and decreased visual acuity. About 40 percent of people with KSS experience profound visual problems.

The third primary finding in people with Kearns-Sayre Syndrome is an interference with the transfer of nerve impulses (conduction) that control the activity of heart muscles (heart block). The severity of such conduction abnormalities may vary among affected individuals.

The normal heart has four chambers. The two upper chambers, known as atria, are separated from each other by a fibrous partition known as the atrial septum. The two lower chambers are known as ventricles and are separated from each other by the ventricular septum. Valves connect the atria (left and right) to their respective ventricles. In the mild form of heart block, the two upper chambers of the heart (atria) beat normally, but the contractions of the two lower chambers (ventricles) slightly lag behind. In the more severe forms, only a half to a quarter of the atrial beats are conducted to the ventricles. In complete heart block, the atria and ventricles beat separately. In some cases, heart block may lead to blackouts (syncope), breathlessness, and/or irregular heartbeats (arrhythmias).

Individuals with Kearns-Sayre Syndrome may also exhibit a variety of other physical characteristics and symptoms. The number and severity of these symptoms may vary greatly from case to case; in some cases, individuals may exhibit a partial or incomplete form of the disorder. The additional physical characteristics and symptoms associated with Kearns-Sayre Syndrome may include developmental delays; short stature (dwarfism); diminished muscle tone (hypotonia); hearing loss, eventually leading to deafness; mental retardation; progressive memory loss and deterioration of intellectual abilities (dementia), and/or abnormalities affecting various of parts of the brain (e.g., white and gray matter, brain stem, and/or cerebellum).

In some affected individuals, Kearns-Sayre Syndrome may also be associated with several disorders involving the function of structures and organs that secrete hormones into the blood system (multiple endocrine dysfunction). The most common of these disorders occurring in association with KSS include hypoparathyroidism, diabetes mellitus, and/or primary failure of the ovaries or testes (gonads). These disorders may result in short stature, a delay in reaching puberty, excessive fatigue, and/or muscle cramps. The relationship between Kearns-Sayre Syndrome and endocrine abnormalities is not fully understood. (For more information on these disorders, choose "Diabetes Mellitus," or "Hypoparathyroidism" as your search terms in the Rare Disease Database.)

On rare occasions, Kearns-Sayre Syndrome may also be associated with other disorders or conditions including absence of certain reflexes, kidney (renal) abnormalities, and/or Peripheral Neuropathy. Peripheral Neuropathy is a rare disorder that may affect one or several nerves of the body, causing pain and weakness. Peripheral Neuropathy may affect sensory, motor, reflex, or blood vessel function. (For more information on this disorder, choose "Peripheral Neuropathy" as your search term in the Rare Disease Database.)

The exact cause of Kearns-Sayre Syndrome is not known. Most cases of KSS appear to occur randomly, for no apparent reason (spontaneously). Most of the research reported in the literature suggests that Kearns-Sayre Syndrome is caused by a loss (deletion) of a large amount of genetic material found in the DNA of mitochondria (mtDNA). Mitochondria, which are found by the hundreds in the cells of the body, particularly in muscle and nerve tissue, carry the blueprints for regulating energy production. As opposed to the genetic instructions of cellular chromosomes (autosomal DNA), which are found within the nucleus of each cell, mitochondrial genetic instructions are found outside of the nucleus of the cell.

In extremely rare cases, these change(s) in mitochondrial genetic material (mutation[s]) may be inherited from the mother. The genetic instructions for mitochondria (mtDNA) found in sperm cells typically break off during fertilization. As a result, it is thought that human mtDNA comes from the mother. An affected mother may pass the mutation(s) on to all her children but only her daughters will pass the mutation(s) on to their children.

The number of defective mitochondria may be outnumbered by the number of normal mitochondria. Symptoms of Kearns-Sayre Syndrome may not appear in any given generation until the mutation(s) or defect(s) affect a significant proportion of mitochondria. The uneven distribution of normal and mutant mtDNA in different tissues can affect different organs in members of the same family. This can result in a variety of symptoms in affected family members.

Kearns-Sayre Syndrome is a rare neuromuscular mitochondrial disorder that affects males and females in equal numbers. Onset is typically before the age of 20; however, symptoms may appear during infancy or adulthood. Eye abnormalities and developmental delays are often observed before the age of five.

Some researchers believe that mitochondrial myopathies may go unrecognized and underdiagnosed in the general population, making it difficult to determine the true frequency of disorders like Kearns-Sayre Syndrome.

Symptoms of the following disorders can be similar to those of Kearns Sayre Syndrome. Comparisons may be useful for a differential diagnosis:

MELAS Syndrome (Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, and Stroke-like episodes), an extremely rare disorder, is one of a group of rare neuromuscular disorders known as mitochondrial encephalomyopathies. Mitochondrial encephalomyopathies are disorders in which a defect in the genetic material arises from a part of the cell structure that regulates energy production (mitochondria), causing the brain and muscles to function improperly (encephalomyopathies). The distinguishing feature in MELAS Syndrome is the recurrence of stroke-like symptoms. Episodes of sudden headaches with vomiting and seizures may begin any time between the ages of five to 40 years. Muscular weakness on one side of the body (hemiparesis), blindness due to lesions in the area of the brain that regulates vision (cortical blindness), and/or impaired vision or blindness in one half of the visual field (hemianopsia) may also occur. In addition, individuals with MELAS Syndrome may also exhibit an abnormal accumulation of lactic acid in the blood (lactic acidosis), progressive dementia, and short stature. (For more information on this disorder, choose "MELAS" as your search term in the Rare Disease Database.)

MERRF Syndrome (Myoclonus Epilepsy associated with Ragged-Red Fibers) is an extremely rare disorder belonging to a group of rare neuromuscular disorders known as mitochondrial encephalomyopathies. Mitochondrial encephalomyopathies are disorders in which a defect in the genetic material arises from a part of the cell structure that releases energy (mitochondria), causing the brain and muscles to function improperly (encephalomyopathies). The distinguishing feature in MERRF Syndrome is sudden, brief, jerking spasms that can affect the arms and legs (limbs) or the entire body (myoclonic seizures). In addition, individuals with MERRF Syndrome may have an abnormal accumulation of lactic acid in the blood (lactic acidosis); impaired ability to coordinate movements (ataxia); muscle weakness; difficulty speaking (dysarthria); degeneration of the optic nerve (optic atrophy); and/or rapid, involuntary movements of the eyes (nystagmus). Short stature and hearing loss are also common symptoms. The symptoms of MERRF Syndrome may begin in childhood or early adult life and progressively worsen. (For more information on this disorder, choose "MERRF" as your search term in the Rare Disease Database.)

Leigh's Disease is a rare inherited neurometabolic disorder. It is characterized by the degeneration of the central nervous system (i.e., brain, spinal cord, and optic nerve). The symptoms of Leigh's Disease usually begin between the ages of three months and two years. Symptoms are associated with progressive neurological deterioration and may include loss of previously acquired motor skills, loss of appetite, vomiting, irritability, and/or seizures. As Leigh's Disease progresses, symptoms may also include generalized weakness, lack of muscle tone (hypotonia), and episodes of elevated levels of lactic acid in the blood (lactic acidosis), which may lead to impairment of respiratory and kidney function. In most cases, Leigh's Disease is inherited as an autosomal recessive genetic trait. However, X-linked recessive and mitochondrial inheritance have also been noted. There appear to be several different types of mitochondrial and genetically determined enzyme defects that can cause Leigh's Disease. (For more information on this disorder, choose "Leigh's" as your search term in the Rare Disease Database.)

The following disorder may precede the development of Kearns-Sayre Syndrome. It may be helpful in identifying an underlying cause of some forms of this disorder:

Pearson Marrow-Pancreas Syndrome is an extremely rare disorder characterized by an impaired ability of red blood cells to carry oxygen (sideroblastic anemia), dysfunction of the organ that produces the hormone insulin (pancreas), low birth weight, failure to gain weight and grow at the expected rate (failure to thrive) and/or wasting away (atrophy) or absence of the spleen (asplenia). Other symptoms of this disorder may include the abnormal accumulation of connective tissue (fibrosis) in the pancreas, impaired absorption (malabsorption) of nutrients by the organs of the gastrointestinal tract, and/or an abnormal accumulation of lactic acid in the blood (lactic acidosis). Pearson Marrow-Pancreas Syndrome may be caused by a change in the genetic material (mutation) found in the DNA of mitochondria (mtDNA) that is extremely similar to the mutations found in some cases of Kearns-Sayre Syndrome. Several cases of Pearson Marrow-Pancreas Syndrome have been reported in the medical literature in which affected individuals developed Kearns-Sayre Syndrome later in childhood or adolescence.

Diagnosis
The diagnosis of Kearns-Sayre Syndrome may be suspected when the three primary characteristics associated with this disorder occur in association with one another. These include paralysis of certain eye muscles (chronic progressive external ophthalmoplegia [CPEO]), abnormal coloration of the delicate membrane lining the eyes (atypical retinitis pigmentosa) and other changes in the structures of the eye (pigmentary degeneration of the retina), and disease affecting the heart (cardiomyopathy), especially conduction disorders (e.g., heart block). Diagnosis of Kearns-Sayre Syndrome may be confirmed by a thorough clinical evaluation and a variety of specialized tests.

Such specialized tests may include an electrocardiogram to detect the presence and evaluate the severity of heart block, blood and spinal fluid lactic acid levels, a muscle biopsy to demonstrate the presence of characteristic abnormalities in muscle tissue (ragged-red fibers), and/or a spinal tap to determine whether there are elevated levels of certain cerebrospinal fluid (CSF) proteins. In some cases of Kearns-Sayre Syndrome, the levels of other substances (i.e., serum creatine kinase, blood lactate, gamma globulin, and/or pyruvate) may be elevated in the blood.

Microscopic examination of biopsy tissue samples under an electron microscope may reveal large numbers of abnormal mitochondria in skeletal and eye muscle tissue. In some cases, a CT scan or tomography may be used to identify abnormal accumulation of calcium in and/or lesions affecting certain areas of the brain.

Treatment
Treatment of heart problems in Kearns-Sayre Syndrome may require a pacemaker for atrioventricular (AV) block or drug therapy to regulate the heartbeat (antiarrhythymic drug therapy).

Surgery may be used to correct visual problems; in some cases, whether or not surgery helps to improve vision often depends on how far the retinal changes have advanced. Various devices may help to improve impaired vision in affected individuals. The specific devices and/or surgical treatment techniques used will depend upon the severity and specific combination of visual abnormalities present.

Separate treatment options for associated disorders (e.g., diabetes mellitus or hypoparathyroidism) may be necessary. In some cases, treatment may include hormone replacement therapies. Other treatments will depend on the specific conditions present.

Genetic counseling may be of benefit for affected individuals and their families. A team approach for infants with this disorder may also be of benefit and may include special social support and other medical services including physical and occupational therapies. Other treatment is symptomatic and supportive.

The U.S. Food and Drug Administration (FDA) has granted Orphan Drug designation to CoQ10 (UbiQGel) for the treatment of Kearns-Sayre Syndrome and other mitochondrial cytopathies (July 2000). Clinical trials are expected to be completed in approximately two years. UbiQGel is produced by the Tishcon Corporation of Westbury, New York.

L-Carnitine (a specialized amino acid) and vitamin therapy including coenzyme Q10, riboflavin, and vitamins C and K are being tested as possible treatments for mitochondrial disorders. These options may be used alone or in conjunction with one another for the treatment of mitochondrial disorders. More studies are needed to determine the long-term safety and effectiveness of these potential treatments for mitochondrial disorders such as Kearns-Sayre Syndrome.

McKusick VA, ed. Online Mendelian Inheritance in Man (OMIM). Baltimore. MD: The Johns Hopkins University; Entry No:530000; Last Update:12/29/98.

TEXTBOOKS
Buyce ML, ed. Birth Defects Encyclopedia. Dover, MA: Blackwell Scientific Publications; For: The Center for Birth Defects Information Services Inc; 1990:1001-4, 1485-1486.

Scriver CR, et al, eds. The Metabolic and Molecular Basis of Inherited Disease. 7th Ed. New York, NY; McGraw-Hill Companies, Inc; 1995:1571-1575.

Bennett JC, Plum F, eds. Cecil Textbook of Medicine. 20th ed. Philadelphia, PA: W.B. Saunders Co; 1996:2167.

Fauci AS, et al, eds. Harrison's Principles of Internal Medicine, 14th Ed. New York, NY: McGraw-Hill, Inc; 1998:2454, 2480.

Beers MH, Berkow R, eds. The Merck Manual, 17th ed. Whitehouse Station, NJ: Merck Research Laboratories; 1999:2454, 2480.

Beers MH, Berkow R, eds. The Merck Manual, 17th ed. Whitehouse Station, NJ: Merck Research Laboratories; 1999:2478.

Behrman RE, ed. Nelson Textbook of Pediatrics, 15th ed. Philadelphia, PA: W.B. Saunders Company; 1996:984.

Lyon G, et al, eds. Neurology of Hereditary Metabolic Diseases in Childhood. 2nd ed. New York, NY: McGraw-Hill Companies; 1996:255.

JOURNAL ARTICLES
Kearns TP, et al. Retinitis pigmentosa, external ophthalmoplegia, and complete heart block: unusual syndrome with histologic study in one of two cases. Arch Ophthalmol. 1958;60:280-289.

Marin-Garcia J, et al. Kearns-Sayre syndrome with a novel mitochondrial DNA deletion. J Child Neurol. 2000;15:555-558.

Gal R, et al. Progressive ptosis in children as a presenting sign of Kearns-Sayre syndrome. Harefuah. 2000;138:108-110, 174.

Becher MW, et al. Kearns-Sayre syndrome with features of Pearson's marrow-pancreas syndrome and a novel 2905-base pair mitochondrial DNA deletion. Hum Pathol. 1999;30:577-581.

Zanssen S, et al. Mitochondrial cytochrome B gene deletion in Kearns-Sayre syndrome associated with a subclinical type of peripheral neuropathy. Clin Neuropathol. 1998;17:291-296.

Poulton J, et al. Duplications of mitochondrial DNA in Kearns-Sayre syndrome. Muscle Nerve. 1995;3:S154-158.

Barrientos A, et al. Progressive external ophthalmoplegia and the Kearns-Sayre syndrome: a clinical and molecular study of 6 cases. Med Clin. 1995;105:180-184.

Nakagawa E, et al. Progressive brainstem and white matter lesions in Kearns-Sayre syndrome: a case report. Brain Dev. 1994;16:416-418.

Norby S, et al. Juvenile Kearns-Sayre syndrome initially misdiagnosed as a psychosomatic disorder. J Med Genet. 1994;31:45-50.

Perocchio M, et al. Mitochondrial disease and complete heart block. Kearns-Sayre syndrome. Description of a case. Minerva Med. 1992;83:7-13.

Gross-Jendroska M, et al. Kearns-Sayre syndrome: a case report and review. Eur J Ophthalmol. 1992;2:15-20.

Harvey JN, et al. Endocrine dysfunction in Kearns-Sayre syndrome. Clin Endocrinol. 1992;37:97-103.

Shoffner JM, et al. Spontaneous Kearns-Sayre syndrome/chronic external ophthalmoplegia plus syndrome associated with a mitochondrial DNA deletion: a slip-replication model and metabolic therapy. Proc Natl Acad Sci USA. 1989;86:7952-7956.

Ogasahara S, et al. Treatment of Kearns-Sayre syndrome with coenzyme Q10. Neurology. 1986;36:45-53.