[Phenotype heterogeneity associated with mitochondrial DNA A3243G mutation].

OBJECTIVE: To discuss the clinical characteristics associated with mitochondrial DNA A3243G mutation. METHODS: Clinical manifestations as well as results of brain CT and/or MRI scanning, blood level of lactic acid and muscle biopsy results of 25 mitochondrial encephalomyopathies patients whose A3243G mutations were analyzed. RESULTS: Although all of the 25 patients carried mtDNA A3243G point mutation, their clinical manifestations varied greatly. Among them, there were 19 cases of mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS), 2 cases of encephalopathies which could not be classified into any specific type, 2 cases of floppy infants, one case of Kearns-Sayer syndrome (KSS) and one case of mitochondrial entero-myopathy. Most patients showed abnormal cranial radiological findings and ragged-red-fibers on muscle biopsies. Elevation of blood lactic acid was notably found in all of the 25 patients. CONCLUSIONS: Significant variations in clinical manifestation and brain images are the prominent features in patients with A3243G mutation. Mitochondrial diseases should be considered in patients with multiple organ involvement and elevated serum lactic acid mtDNA mutation examination is necessary for the diagnosis of mitochondrial diseases.

Clinical laboratory monitoring of coenzyme Q10 use in neurologic and muscular diseases.

Coenzyme Q10 (Q10) is available as an over-the-counter dietary supplement in the United States. While its use could be considered a form of alternative therapy, the medical profession has embraced the use of Q10 in specific disease states, including a series of neurologic and muscular diseases. Clinical laboratory monitoring is available for measurement of total Q10 in plasma and tissue and for measurement of redox status, ie, the ratio of reduced and oxidized forms of Q10. Many published studies have been anecdotal, in part owing to the rarity of some diseases involved. Unfortunately, many studies do not report Q10 levels, and, thus, the relationship of clinical response to Q10 concentration in plasma frequently is not discernible. Consistent laboratory monitoring of patients treated with this compound would help ease interpretation of the results of the treatment, especially because so many formulations of Q10 exist in the marketplace, each with its own bioavailability characteristics. Q10 has an enviable safety profile and, thus, is ideal to study as an adjunct to more conventional therapy. Defining patient subpopulations and characteristics that predict benefit from exogenous Q10 and defining therapeutic ranges for those particular applications are major challenges in this field.

Recognition of mitochondrial DNA deletion syndrome with non-neuromuscular multisystemic manifestation.

PURPOSE: To correlate the molecular characteristics of the mtDNA deletions with clinical phenotypes. METHODS: Southern analysis and polymerase chain reaction (PCR)/DNA sequencing were used to determine the size and location of deletions in 16 patients with mtDNA deletion syndrome. An additional 48 reported cases from the literature were also included in the statistical analysis. RESULTS: The common 5-kb deletion is found in eight of nine patients with Kearns-Sayre syndrome (KSS), mitochondrial myopathies (MM), or progressive external ophthalmoplegia (PEO). The rare/novel deletions were found in six of seven patients with extra-neuromuscular multisystemic manifestations and infantile/early childhood onset. CONCLUSIONS: Patients with mtDNA deletion syndrome who manifest non-neuromuscular multisystemic disorders at a very young age usually harbor mutant mtDNA with novel or rare deletions in every tissue analyzed. For this group of patients, it is possible to use the less invasive blood specimens instead of muscle biopsies for molecular diagnosis. Overwhelmingly, the common 5-kb deletion is mostly seen in the muscle specimens of patients with KSS and age of onset after the second decade of life.

Severe hypomagnesemia and hypoparathyroidism in Kearns-Sayre syndrome.

Kearns-Sayre syndrome (KSS) is a multisystem mitochondrial disorder characterized by the invariant triad: onset before 20, progressive external ophthalmoplegia and pigmentary retinal degeneration, plus at least one of the following: complete heart block, cerebellar dysfunction and CSF protein >100 mg/dl. Autopsies from patients with KSS revealed widespread tissue distribution of mitochondrial (mt) DNA deletions. These deletions result in significantly lower activities of the enzymes of the respiratory chain. KSS has been associated with a variety of endocrine and metabolic disorders in <10% of patients, while renal tubular involvement is extremely rare. We present an 18-year-old girl with KSS who developed hypoparathyroidism and renal tubular dysfunction with inappropriate mangesiuria and kaliuria. We further discuss the renal tubular damage in KSS emphasizing its pathophysiology and clinical phenotype, and review the possible mechanisms of hypoparathyroidism in KSS.

Kearns-Sayre syndrome presenting as 2-oxoadipic aciduria.

A patient with 2-oxoadipic aciduria and 2-aminoadipic aciduria presented at 2 years of age with manifestations typical of organic acidemia, episodes of ketosis and acidosis, progressive to coma. This resolved and the key metabolites disappeared from the urine and blood. At 9 years of age she developed typical Kearns-Sayre syndrome with complete heart block, retinopathy, and ophthalmoplegia. Southern blot revealed a deletion in the mitochondrial genome.

A case of Kearns-Sayre syndrome showing a constant proportion of deleted mitochondrial DNA in blood cells during 6 years of follow-up.

Kearns-Sayre syndrome (KSS) and Pearson syndrome (PS) show quite different phenotypes despite the same underlying genetic defect, i.e. a large deletion of one population of mitochondrial (mt) DNA. The main feature of KSS is progressive encephalomyopathy; on the other hand, PS shows fatal hematological problems in early infancy. Through Southern blot analysis of mtDNA of blood cells, deletion has been consistently found in patients with PS but usually undetectable in KSS patients. Therefore, their different clinical phenotypes have been explained by the different tissue distribution of mutant mtDNA. Recently, a few cases were reported which had features of PS in infancy and later developed KSS. These observations suggest that phenotypes may also be modified by the selection process involving mtDNA within different tissues. We found a case of KSS, who initially presented endocrinological dysfunction such as insulin-dependent diabetes mellitus (IDDM) and growth hormone (GH) deficiency, and had not developed external ophthalmoplegia until the age of 17. Although he did not show any symptoms of PS, a marked proportion of mtDNA was deleted not only in muscle but also in blood cells. Analysis of his blood cells showed an unchanged proportion of deleted mtDNA at three estimations within 6 years of the follow-up period. This case provides evidence that deleted mtDNA in blood cells also has a stable replicative capacity and that a large proportion of deleted mtDNA in blood cells may not accompany hematological problems.

The influence of Coenzyme Q10 on total serum calcium concentration in two patients with Kearns-Sayre Syndrome and hypoparathyroidism.

Two patients with Kearns-Sayre Syndrome and hypoparathyroidism were treated with alfacalcidol (1a-OH D3) and total serum calcium concentration remained within normal range for a long period. After two months of combined therapy with Coenzyme Q10 (CoQ10), hypercalcemia was noticed and as a result, 1a-OHD3 was gradually discontinued. Normal total serum calcium concentration was obtained with CoQ10 monotherapy while the replacement of CoQ10 with placebo led to hypocalcemia. The mechanism of action of CoQ10 is difficult to explain. Since the parathormone level remained unchanged during CoQ10 or placebo therapy, we speculate that the capacity of producing an active form of vitamin D in mitochondria of proximal tubules was restored by CoQ10 therapy.

[The Kearns-Sayre syndrome]. / La sindrome di Kearns-Sayre.

A case of Kearns-Sayre syndrome with hyperlactacidaemia was reported and the relationships between the syndrome and the mitochondrial cytopathies are discussed, on clinical, genetical and therapeutic ground. Positive results in the reported case were observed with a reduced carbohydrates, high fat diet, in order to lowering the hyperlactacidaemia.

Detection of platelet mitochondrial DNA deletions in Kearns-Sayre syndrome.

To establish a noninvasive genetic diagnosing method for Kearns-Sayre syndrome, the authors used the polymerase chain reaction (PCR) technique for detecting mitochondrial DNA (mtDNA) deletions in the platelets and directly sequenced the crossover regions of the deleted mtDNA using the fluorescence-based automated sequencing system. The mtDNA deletions were identified in the platelets of three of four patients. The sizes and locations of deletions were determined by the nesting primer PCR method, in which the primary PCR products derived from deleted mtDNAs undergo reamplification using a series of nesting primers. With the fluorescence-based sequencing of templates amplified by the asymmetric PCR method, deleted mtDNA was sequenced directly without cloning. In patient 1, guanine (G) was found at the boundaries of a deleted segment spanning 8400 base pairs (bp) between the CO1 and ND6 genes. In patient 2, a 9-bp directly repeated sequence of 5'-ACCTCCCTC-3' (where A = adenine, C = cytosine, and T = thymine) was found at the boundaries of a deleted segment spanning 7221 bp between the CO1 and ND5 genes. In patient 3, an 8-bp sequence of 5'-TCGCTGTC-3' was found at the boundaries of a deleted segment spanning 4664 bp between the ATPase6 and ND5 genes. Deletions were not detected in the mtDNA of patient 4 or in that of the mothers of the patients. Previously, the genetic diagnosis of this syndrome required muscle biopsy specimens and the use of Southern blot analysis. However, this method requires neither muscle biopsy nor isotopes and is more rapid than the Southern blot method.(ABSTRACT TRUNCATED AT 250 WORDS)

Diabetes mellitus in Kearns-Sayre syndrome.

A 20-year-old woman with Kearns-Sayre syndrome (KSS) suddenly experienced two episodes of diabetic coma. She was studied to determine whether diabetes mellitus (DM) resulted from insulin resistance or from an insulin secretion abnormality, using the euglycemic glucose clamp technique and the glucagon tolerance test. She had a deficiency of insulin secretion from beta cells. It is important to recognize in practice the onset of DM in patients with mitochondrial myopathy. We would suggest that a genetic linkage or mitochondrial dysfunction may be responsible for the association of both disease states.

Improvement of abnormal pyruvate metabolism and cardiac conduction defect with coenzyme Q10 in Kearns-Sayre syndrome.

In a patient with Kearns-Sayre syndrome, concentration of coenzyme Q10, a component of the mitochondrial electron transport system, was decreased in serum and in the mitochondrial fraction of skeletal muscle. Serum concentrations of lactate and pyruvate were abnormally high, especially after exercise or oral glucose loading. Levels of folic acid in plasma and CSF were decreased. ECG showed a first-degree atrioventricular block. After administration of coenzyme Q10 60 to 120 mg daily for 3 months, serum levels of lactate and pyruvate became normal, with improvement of atrioventricular block and ocular movements.