Normal muscle respiratory chain enzymes can complicate mitochondrial disease diagnosis.
This report presents a case of mitochondrial respiratory chain deficiency in a neonate with elevated plasma lactate, hypotonia, developmental delay, and dysmorphic features. The initial biochemical analyses of muscle tissue for mitochondrial function were normal. Additional testing on skin fibroblasts performed owing to a high clinical suspicion of a possible mitochondrial disorder indicated a deficiency of mitochondrial complex I. Western blotting of samples obtained both from muscle and fibroblast tissues also revealed an extensive defect in mitochondrial respiratory chain complex I, confirming the diagnosis. These observations underscore the fact that both enzymatic and immunological assays should be undertaken in alternate tissues when muscle biopsies are inconclusive in highly suspected cases.
Oglesbee
Devin
D
Biochemical Genetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.
Freedenberg
Debra
D
Kramer
Karen A
KA
Anderson
Bambi D
BD
Hahn
Si Houn
SH
D000140:Acidosis, Lactic / Q000175:diagnosis / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D001284:Atrophy; D001706:Biopsy; D015153:Blotting, Western; D002331:Carnitine / Q000031:analogs & derivatives / Q000097:blood; D020863:Central Nervous System Cysts / Q000175:diagnosis / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D002552:Cerebral Ventricles / Q000473:pathology; D004252:DNA Mutational Analysis; D003937:Diagnosis, Differential; D042967:Electron Transport Complex I / Q000172:deficiency* / Q000235:genetics; D005260:Female; D005347:Fibroblasts / Q000201:enzymology / Q000473:pathology; D005625:Frontal Lobe / Q000473:pathology; D006801:Humans; D007231:Infant, Newborn; D008279:Magnetic Resonance Imaging; D028361:Mitochondrial Diseases / Q000175:diagnosis* / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D018482:Muscle, Skeletal / Q000201:enzymology* / Q000473:pathology; D009413:Nerve Fibers, Myelinated / Q000473:pathology; D017354:Point Mutation
C116917:acylcarnitine; D042967:Electron Transport Complex I; D002331:Carnitine