Late-onset MNGIE without peripheral neuropathy due to incomplete loss of thymidine phosphorylase activity.
Mitochondrial NeuroGastroIntestinal Encephalomyopathy (MNGIE) is an autosomal recessive disorder characterized by severe gastrointestinal dysmotility, cachexia, peripheral neuropathy, ptosis, ophthalmoplegia, and leukoencephalopathy with early onset and severe prognosis. Mutations in the TYMP/ECGF1 gene cause a loss of thymidine phosphorylase catalytic activity, disrupting the homeostasis of intramitochondrial nucleotide pool. We report a woman with a very late onset of MNGIE, lacking peripheral neuropathy. Thymidine phosphorylase activity was markedly reduced in cultured fibroblasts, but only mildly reduced in buffy coat, where the defect is usually detected, and plasma thymidine was mildly increased compared to typical MNGIE patients. TYMP/ECGF1 analysis detected two heterozygous mutations, including a novel missense mutation. These findings indicate that a partial loss of thymidine phosphorylase activity may induce a late-onset and incomplete MNGIE phenotype.
Massa
Roberto
R
Department of Neurosciences, University of Rome-Tor Vergata and IRCCS-Fondazione S. Lucia, Via Montpellier 1, I-00135 Rome, Italy. massa@uniroma2.it
Tessa
Alessandra
A
Margollicci
Maria
M
Micheli
Vanna
V
Romigi
Andrea
A
Tozzi
Giulia
G
Terracciano
Chiara
C
Piemonte
Fiorella
F
Bernardi
Giorgio
G
Santorelli
Filippo M
FM
D017668:Age of Onset; D001921:Brain / Q000473:pathology / Q000503:physiopathology; D002478:Cells, Cultured; D005260:Female; D005347:Fibroblasts / Q000201:enzymology; D006801:Humans; D008875:Middle Aged; D017237:Mitochondrial Encephalomyopathies / Q000097:blood / Q000235:genetics* / Q000503:physiopathology*; D009154:Mutation; D020125:Mutation, Missense; D010525:Peripheral Nerves / Q000503:physiopathology; D010641:Phenotype; D013936:Thymidine / Q000097:blood; D013939:Thymidine Phosphorylase / Q000172:deficiency* / Q000235:genetics
C543750:TYMP protein, human; D013939:Thymidine Phosphorylase; D013936:Thymidine