Abstract
BackgroundTTC19 deficiency is a progressive neurodegenerative disease associated with isolated mitochondrial respiratory chain (MRC) complex III deficiency and loss-of-function mutations in the TT19 gene in the few patients reported so far.MethodsWe performed exome sequencing and selective mutational analysis of TTC19, respectively, in patients from three unrelated families presenting with initially unspecific clinical signs of muscular hypotonia and global developmental delay followed by regression, ataxia, loss of speech, and rapid neurological deterioration. One patient showed severe lactic acidosis at the neonatal age and during intercurrent illness.ResultsWe identified homozygous mutations in all three index cases, in two families novel missense mutations (c.544 T > C/p.Leu185Pro; c.917 T > C/p.Leu324Pro). The younger sister of the severely affected patient 3 showed only mild delay of motor skills and muscular hypotonia so far but is also homozygous for the same mutation. Notably, one patient revealed normal activities of MRC complex III in two independent muscle biopsies. Neuroimaging of the severely affected patients demonstrated lesions in putamen and caudate nuclei, cerebellar atrophy, and the unusual finding of hypertrophic olivary nuclei degeneration. Reviewing the literature revealed striking similarities regarding neuroimaging and clinical course in pediatric patients with TTC19 deficiency: patterns consistent with Leigh or Leigh-like syndrome were found in almost all, hypertrophic olivary nucleus degeneration in all patients reported so far. The clinical course in pediatric patients is characterized by an initially unspecific developmental delay, followed by regression, progressive signs and symptoms of cerebellar, basal ganglia and brainstem affection, especially loss of speech and ataxia. Subsequently, neurological deterioration leading to a vegetative state occurs.ConclusionsOur findings add to the phenotypic, genetic, and biochemical spectrum of TTC19 deficiency. However, TTC19 deficient patients do show characteristic clinical and neuroimaging features, which may facilitate diagnosis of this yet rare disorder. Normal MRC complex III activity does not exclude the diagnosis.
Highlights
TTC19 deficiency is a progressive neurodegenerative disease associated with isolated mitochondrial respiratory chain (MRC) complex III deficiency and loss-of-function mutations in the TT19 gene in the few patients reported so far
Biochemical, and molecular phenotypes of four pediatric patients with TTC19 deficiency identified by exome sequencing and selective mutation analysis, respectively
The boy had four older healthy siblings (1 sister, 3 brothers). He presented with severe lactic acidosis in the neonatal age and during intercurrent infections at the age of 4 months (RSV), 5 months, 10 months, and 16 months
Summary
TTC19 deficiency is a progressive neurodegenerative disease associated with isolated mitochondrial respiratory chain (MRC) complex III deficiency and loss-of-function mutations in the TT19 gene in the few patients reported so far. The TTC19 protein (NP_060245) has been characterized as a high molecular weight complex, which is embedded in the inner mitochondrial membrane and has been reported to be involved in the assembly and activation of mitochondrial respiratory chain (MRC) complex III [1]. TTC19 loss-of-function mutations (4 nonsense mutations, 1 deletion of 4 base pairs, 2 duplications of 2 and 17 base pairs, respectively) have been identified leading to premature protein truncation or nonsense-mediated RNA decay. The biochemical feature indicative for mutations in TTC19 is an isolated deficiency of mitochondrial respiratory chain (MRC) complex III [1,2,3,4,6]. Severe lactic acidosis in blood has not been reported in these patients
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
