Purpose: The purpose of this statement is to review the literature regarding mitochondrial disease and to provide recommendations for optimal diagnosis and treatment. This statement is intended for physicians who are engaged in diagnosing and treating these patients. Methods: The Writing Group members were appointed by the Mitochondrial Medicine Society. The panel included members with expertise in several different areas. The panel members utilized a comprehensive review of the literature, surveys, and the Delphi method to reach consensus. We anticipate that this statement will need to be updated as the field continues to evolve. Results: Consensus-based recommendations are provided for the diagnosis and treatment of mitochondrial disease. Conclusion: The Delphi process enabled the formation of consensus-based recommendations. We hope that these recommendations will help standardize the evaluation, diagnosis, and care of patients with suspected or demonstrated mitochondrial disease. Genet Med 17 9, 689–701.

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. The panel included members with several different areas of expertise. The panel members utilized surveys and the Delphi method to reach consensus. We anticipate that this statement will need to be updated as the field continues to evolve. Consensus-based recommendations are provided for the routine care and management of patients with primary genetic mitochondrial disease.

Notorious variability in the presentation of mitochondrial disease in the infant and young child complicates its clinical diagnosis. Mitochondrial disease is not a single entity but, rather, a heterogeneous group of disorders characterized by impaired energy production due to genetically based oxidative phosphorylation dysfunction. Together, these disorders constitute the most common neurometabolic disease of childhood with an estimated minimal risk of developing mitochondrial disease of 1 in 5000. Diagnostic difficulty results from not only the variable and often nonspecific presentation of these disorders but also from the absence of a reliable biomarker specific for the screening or diagnosis of mitochondrial disease. A simplified and standardized approach to facilitate the clinical recognition of mitochondrial disease by primary physicians is needed. With this article we aimed to improve the clinical recognition of mitochondrial disease by primary care providers and empower the generalist to initiate appropriate baseline diagnostic testing before determining the need for specialist referral. This is particularly important in light of the international shortage of metabolism specialists to comprehensively evaluate this large and complex disease population. It is hoped that greater familiarity among primary care physicians with the protean manifestations of mitochondrial disease will facilitate the proper diagnosis and management of this growing cohort of pediatric patients who present across all specialties.

Eric Pierce, Xiaowu Gai and colleagues identify mutations in NMNAT1 as a new cause of Leber congenital amaurosis, an early-onset form of retinal degeneration. NMNAT1 encodes an isoform of nicotinamide mononucleotide adenylyltransferase, which is required for nicotinamide adenine dinucleotide (NAD+) biosynthesis. Leber congenital amaurosis (LCA) is an infantile-onset form of inherited retinal degeneration characterized by severe vision loss1,2. Two-thirds of LCA cases are caused by mutations in 17 known disease-associated genes3 (Retinal Information Network (RetNet)). Using exome sequencing we identified a homozygous missense mutation (c.25G>A, p.Val9Met) in NMNAT1 that is likely to be disease causing in two siblings of a consanguineous Pakistani kindred affected by LCA. This mutation segregated with disease in the kindred, including in three other children with LCA. NMNAT1 resides in the previously identified LCA9 locus and encodes the nuclear isoform of nicotinamide mononucleotide adenylyltransferase, a rate-limiting enzyme in nicotinamide adenine dinucleotide (NAD+) biosynthesis4,5. Functional studies showed that the p.Val9Met alteration decreased NMNAT1 enzyme activity. Sequencing NMNAT1 in 284 unrelated families with LCA identified 14 rare mutations in 13 additional affected individuals. These results are the first to link an NMNAT isoform to disease in humans and indicate that NMNAT1 mutations cause LCA.