MedGen

Fumarate hydratase (FH) deficiency results in severe neonatal and early infantile encephalopathy that is characterized by poor feeding, failure to thrive, hypotonia, lethargy, and seizures. Dysmorphic facial features include frontal bossing, depressed nasal bridge, and widely spaced eyes. Many affected individuals are microcephalic. A spectrum of brain abnormalities are seen on magnetic resonance imaging, including cerebral atrophy, enlarged ventricles and generous extra-axial cerebral spinal fluid (CSF) spaces, delayed myelination for age, thinning of the corpus callosum, and an abnormally small brain stem. Brain malformations including bilateral polymicrogyria and absence of the corpus callosum can also be observed. Development is severely affected: most affected individuals are nonverbal and nonambulatory, and many die during early childhood. Less severely affected individuals with moderate cognitive impairment and long-term survival have been reported. [from GeneReviews]

Any combined oxidative phosphorylation deficiency in which the cause of the disease is a mutation in the LYRM4 gene. [from MONDO]

Mitochondrial complex I deficiency nuclear type 29 (MC1DN29) is an autosomal recessive metabolic disorder that usually presents in childhood, adolescence, or adulthood with exercise intolerance and easy fatigue with myalgias and muscle weakness. However, a severe multisystem presentation with chronic renal failure and cardiomyopathy in infancy has been reported (Sanchez-Caballero et al., 2016; Alston et al., 2016). For a discussion of genetic heterogeneity of mitochondrial complex I deficiency, see 252010. [from OMIM]

The mitochondrial matrix refers to the substance occupying the space enclosed by the inner membrane of a mitochondrion, which contains enzymes, DNA, granules, and inclusions of protein crystals, glycogen, and lipid. Mitochondrial swelling refers to an increase in size of the mitochondrial matrix. This phenomenon is thought to be related to a permeabilized inner membrane that originates a large swelling in the mitochondrial matrix. Mitochondrial swelling may distend the outer membrane until it ruptures. [from HPO]