Patient care standards for primary mitochondrial disease: a consensus statement from the Mitochondrial Medicine Society.

The purpose of this statement is to provide consensus-based recommendations for optimal management and care for patients with primary mitochondrial disease. This statement is intended for physicians who are engaged in the diagnosis and management of these patients. Working group members were appointed by the Mitochondrial Medicine Society.

Recommendations for the Management of Strokelike Episodes in Patients With Mitochondrial Encephalomyopathy, Lactic Acidosis, and Strokelike Episodes.

Importance: Strokelike episodes are a cardinal feature of several mitochondrial syndromes, including mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes (MELAS). Recent advances in the understanding of the pathophysiologic mechanisms of strokelike episodes in MELAS have led to improved treatment options.

Observations: Current understanding of the cause of strokelike episodes in MELAS and present recommendations to assist in the identification and treatment of patients with MELAS who present with stroke are presented.

Self-reported treatment-associated symptoms among patients with urea cycle disorders participating in glycerol phenylbutyrate clinical trials.

Background: Health care outcomes have been increasingly assessed through health-related quality of life (HRQoL) measures. While the introduction of nitrogen-scavenging medications has improved survival in patients with urea cycle disorders (UCDs), they are often associated with side effects that may affect patient compliance and outcomes.

Methods: Symptoms commonly associated with nitrogen-scavenging medications were evaluated in 100 adult and pediatric participants using a non-validated UCD-specific questionnaire.

Blood ammonia and glutamine as predictors of hyperammonemic crises in patients with urea cycle disorder.

Purpose: The aim of this study was to examine predictors of ammonia exposure and hyperammonemic crises in patients with urea cycle disorders.

Methods: The relationships between fasting ammonia, daily ammonia exposure, and hyperammonemic crises were analyzed in >100 patients with urea cycle disorders.

Results: Fasting ammonia correlated strongly with daily ammonia exposure (r = 0.

Methylmalonic acidemia: a megamitochondrial disorder affecting the kidney.

Background: Classical (or isolated) methylmalonic acidemia (MMA) is a heterogeneous inborn error of metabolism most typically caused by mutations in the vitamin B12-dependent enzyme methylmalonyl-CoA mutase (MUT). With the improved survival of individuals with MMA, chronic kidney disease has become recognized as part of the disorder. The precise description of renal pathology in MMA remains uncertain.

Practice patterns of mitochondrial disease physicians in North America. Part 1: diagnostic and clinical challenges.

Mitochondrial medicine is a young subspecialty. Clinicians have a limited evidence base on which to formulate clinical decisions regarding diagnosis, treatment and patient management. Mitochondrial medicine specialists have cobbled together an informal set of rules and paradigms for preventive care and management based in part on anecdotal experience.

Metabolic profiling of total homocysteine and related compounds in hyperhomocysteinemia: utility and limitations in diagnosing the cause of puzzling thrombophilia in a family.

We describe a family illustrating the diagnostic difficulties occurring when pyridoxine-responsive cystathionine beta-synthase (CBS) deficiency presents with thrombotic disease without associated ocular, skeletal, or CNS abnormalities, a situation increasingly recognized. This family had several thromboembolic episodes in two generations with apparently inconstant elevations of plasma total homocysteine (tHcy). When taking (sometimes even low amounts) of pyridoxine, the affected family members had low-normal tHcy and normal values for cystathionine, methionine, and cysteine.

Ammonia control and neurocognitive outcome among urea cycle disorder patients treated with glycerol phenylbutyrate.

Unlabelled: Glycerol phenylbutyrate is under development for treatment of urea cycle disorders (UCDs), rare inherited metabolic disorders manifested by hyperammonemia and neurological impairment. We report the results of a pivotal Phase 3, randomized, double-blind, crossover trial comparing ammonia control, assessed as 24-hour area under the curve (NH3 -AUC0-24hr ), and pharmacokinetics during treatment with glycerol phenylbutyrate versus sodium phenylbutyrate (NaPBA) in adult UCD patients and the combined results of four studies involving short- and long-term glycerol phenylbutyrate treatment of UCD patients ages 6 and above. Glycerol phenylbutyrate was noninferior to NaPBA with respect to ammonia control in the pivotal study, with mean (standard deviation, SD) NH3 -AUC0-24hr of 866 (661) versus 977 (865) μmol·h/L for glycerol phenylbutyrate and NaPBA, respectively.

Maple syrup urine disease in Cypriot families: identification of three novel mutations and biochemical characterization of the p.Thr211Met mutation in the E1alpha subunit.

We report five mutations, three of them novel, responsible for maple syrup urine disease in four unrelated Cypriot families. The five children studied are the first cases of classic maple syrup urine disease to be reported among Cypriots. The first novel mutation identified is a single-base deletion in exon 6 of the Elalpha gene (c.

N-carbamylglutamate markedly enhances ureagenesis in N-acetylglutamate deficiency and propionic acidemia as measured by isotopic incorporation and blood biomarkers.

N-acetylglutamate (NAG) is an endogenous essential cofactor for conversion of ammonia to urea in the liver. Deficiency of NAG causes hyperammonemia and occurs because of inherited deficiency of its producing enzyme, NAG synthase (NAGS), or interference with its function by short fatty acid derivatives. N-carbamylglutamate (NCG) can ameliorate hyperammonemia from NAGS deficiency and propionic and methylmalonic acidemia.

Adenoviral-mediated correction of methylmalonyl-CoA mutase deficiency in murine fibroblasts and human hepatocytes.

Background: Methylmalonic acidemia (MMA), a common organic aciduria, is caused by deficiency of the mitochondrial localized, 5'deoxyadenosylcobalamin dependent enzyme, methylmalonyl-CoA mutase (MUT). Liver transplantation in the absence of gross hepatic dysfunction provides supportive therapy and metabolic stability in severely affected patients, which invites the concept of using cell and gene delivery as future treatments for this condition.

Methods: To assess the effectiveness of gene delivery to restore the defective metabolism in this disorder, adenoviral correction experiments were performed using murine Mut embryonic fibroblasts and primary human methylmalonyl-CoA mutase deficient hepatocytes derived from a patient who harbored two early truncating mutations, E224X and R228X, in the MUT gene.

Newborn screening for hepatorenal tyrosinemia by tandem mass spectrometry: analysis of succinylacetone extracted from dried blood spots.

Objectives: To develop a method for the determination of succinylacetone (SA) in dried blood spots (DBS) using tandem mass spectrometry (MS/MS).

Methods: SA was extracted from DBS with an acetonitrile and water solution (80:20 by volume) containing formic acid and hydrazine hydrate (both at 0.1% by volume), and analyzed by MS/MS with a total run time per sample under 2 min.

Determination of phenylalanine and tyrosine in dried blood specimens by ion-exchange chromatography using the Hitachi L-8800 analyzer.

Objectives: The treatment for phenylketonuria (PKU) includes monitoring blood phenylalanine (Phe) levels on a regular basis. To reduce inconvenience to the patient and family, blood specimens on filter paper can be obtained at home and mailed to the clinic or analytical laboratory. For this reason, we validated an 8-min isothermal and isocratic HPLC method using the Hitachi L-8800 analyzer for quantitation of Phe and tyrosine (Tyr) from dried blood specimens (DBS).

The importance of gut motility in the metabolic control of propionic acidemia.

We hypothesized that gut motility likely plays a critical role in the metabolic stability in propionic acidemia (PA). Therefore, 4 known patients with PA (aged 47 months to 185 months) were prospectively studied over 7 days in the Clinical Research Center at Children's Hospital, Boston. Determinations of ammonia, bicarbonate, and amino acids in blood; organic acids and propionylglycine in urine; and a lactulose breath test were conducted under two study conditions: on regular therapy (for 4 days) and on regular therapy plus Senekot (Purdue Frederick Company, Norwalk, Conn), an intestinal motility agent (for 3 days).

Effect of expanded newborn screening for biochemical genetic disorders on child outcomes and parental stress.

Context: Tandem mass spectrometry now allows newborn screening for more than 20 biochemical genetic disorders. Questions about the effectiveness and risks of expanded newborn screening for biochemical genetic disorders need to be answered prior to its widespread acceptance as a state-mandated program.

Objectives: To compare newborn identification by expanded screening with clinical identification of biochemical genetic disorders and to assess the impact on families of a false-positive screening result compared with a normal result in the expanded newborn screening program.

Improved growth and nutrition status in children with methylmalonic or propionic acidemia fed an elemental medical food.

Background: Failure-to-thrive (FTT) has been described in patients with organic acidemias treated with low protein diets.

Objective: To determine if patients with methylmalonic (MMA) or propionic acidemia (PA) can achieve normal growth and nutrition status.

Methods: A 6-month multicenter outpatient study was conducted with infants and toddlers treated with Propimex-1 Amino Acid-Modified Medical Food With Iron (Ross Products Division, Abbott Laboratories, Columbus, OH).

Four cases with hypoplastic thumbs and encephaloceles.

We report on four infants with hypoplastic thumbs and occipital encephaloceles. None had either a chromosome abnormality or a family history of any major malformation. The literature and database were searched intensively.

Rod photoreceptor function in children with mitochondrial disorders.

Objective: To test the hypothesis that function of the rod photoreceptors is abnormal in pediatric patients with mitochondrial disorders.

Methods: Patients (n = 22; median age, 5 years) with a deficiency of 1 or more of the mitochondrial enzyme complexes, or a mutation in mitochondrial DNA, were studied by means of scotopic, full-field electroretinography (ERG). The conditions of ERG testing allowed derivation of the parameters of the activation of rod phototransduction from the ERG a-wave, and postreceptoral function from b-wave and P(2) stimulus-response functions.