Muscle involvement on MRI is consistent in patients with LGMD2C-F and can be helpful in distinguishing sarcoglycanopathies from other LGMDs or dystrophinopathies, which represent the most common differential diagnoses. Our data provide evidence about selective susceptibility or resistance to degeneration of specific muscles when one of the sarcoglycans is deficient, as well as preliminary information about progressive involvement of the different muscles over time.
When discussing the test with patients, the physician should reassure the patient and parents regarding the degree of pain that may be encountered, which is not materially different from venipuncture. Muscle Nerve 54: 422-426, 2016.
Congenital neurological disorders are genetically highly heterogeneous. Rare forms of hereditary neurological disorders are still difficult to be adequately diagnosed. Pertinent studies, especially when reporting only single families, need independent confirmation. We present three unrelated families in which whole-exome sequencing identified the homozygous non-sense variants c.430[C>T];[C>T] p.(Arg144*), c.1219[C>T];[C>T] p.(Gln407*) and c.1408[C>T];[C>T] p.(Arg470*) in GTPBP2. Their clinical presentations include early onset and apparently non-progressive motor and cognitive impairment, and thereby overlap with findings in a recently described family harbouring a homozygous GTPBP2 splice site variant. Notable differences include structural brain abnormalities (e.g., agenesis of the corpus callosum, exclusive to our patients), and evidence for brain iron accumulation (exclusive to the previously described family). This report confirms pathogenicity of biallelic GTPBP2 inactivation and broadens the phenotypic spectrum. It also underlines that a potential involvement of brain iron accumulation needs clarification. Further patients will have to be identified and characterised in order to fully define the core features of GTPBP2-associated neurological disorder, but future approaches to molecular diagnosis of neurodevelopmental disorders should implement GTPBP2.
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