Cortical atrophy and hypofibrinogenemia due to FGG and TBCD mutations in a single family: a case report
BMC MEDICAL GENETICS
Authors: Stephen, Joshi; Nampoothiri, Sheela; Vinayan, K. P.; Yesodharan, Dhanya; Remesh, Preetha; Gahl, William A.; Malicdan, May Christine, V
Abstract
Background: Blended phenotypes or co-occurrence of independent phenotypically distinct conditions are extremely rare and are due to coincidence of multiple pathogenic mutations, especially due to consanguinity. Hereditary fibrinogen deficiencies result from mutations in the genes FGA, FGB, and FGG, encoding the three different polypeptide chains that comprise fibrinogen. Neurodevelopmental abnormalities have not been associated with fibrinogen deficiencies. In this study, we report an unusual patient with a combination of two independently inherited genetic conditions; fibrinogen deficiency and early onset cortical atrophy. Case presentation: The study describes a male child from consanguineous family presented with hypofibrinogenemia, diffuse cortical atrophy, microcephaly, hypertonia and axonal motor neuropathy. Through a combination of homozygosity mapping and exome sequencing, we identified bi allelic pathogenic mutations in two genes: a homozygous novel truncating mutation in FGG (c.554del; p.Lys185Argfs*14) and a homozygous missense mutation in TBCD (c.1423G > A;p.Ala475Thr). Loss of function mutations in FGG have been associated with fibrinogen deficiency, while the C.1423G > A mutation in TBCD causes a novel syndrome of neurodegeneration and early onset encephalopathy. Conclusions: Our study highlights the importance of homozygosity mapping and exome sequencing in molecular prenatal diagnosis, especially when multiple gene mutations are responsible for the phenotype.
Developmental Regression and Epilepsy of Infancy with Migrating Focal Seizures Caused by TBCD Mutation: A Case Report and Review of the Literature
NEUROPEDIATRICS
Authors: Zhang, Yunjian; Zhang, Linmei; Zhou, Shuizhen
Abstract
Microtubule dynamics plays a crucial role in neuronal development and function. Variants in the tubulin cofactor D ( TBCD ) gene, which encodes one of the five co-chaperones required for assembly and disassembly of alpha/beta-tubulin heterodimers, may lead to neurodevelopmental disorders. We aimed to study the clinical, electroencephalographic, and imaging features of a male patient with TBCD variants, and to provide a detailed review of the previously reported cases of TBCD -related neurological disorders. The patient presented with early-onset developmental regression, secondary microcephaly, epilepsy of infancy with migrating focal seizures, hypotonia, and brain atrophy with thin corpus callosum on brain magnetic resonance imaging. Genetic analyses of the family members revealed a compound heterozygous variant of c.230A > G (p.H77R) in the proband and deletion of exons 28 to 39 of TBCD , which has not been previously reported and was inherited from his carrier parents. Epilepsy of the patient was refractory to numerous antiepileptic drugs. The review of 33 previously reported patients revealed that the age at the onset was very early, and all the patients had presentations during the first year of life. This case report provides insight regarding the clinical features and genetic etiology of TBCD -related tubulinopathy. Identification of phenotypes and genotypes in patients may help in early diagnosis and appropriate genetic counseling.