A case of pseudodominant inheritance of limb-girdle muscular dystrophy caused by mutations in the CAPN3 gene

Introduction. Limb-girdle muscular dystrophy (LGMD) includes more than 30 forms caused by mutations in genes located on autosomes. The most common form is calpain-3-related LGMD, with autosomal recessive inheritance pattern (OMIM 253600). An autosomal dominant form of LGMD (OMIM 618129) caused by c.643_663del heterozygous mutation in the CAPN3 gene is also supposed to exist. This article describes a family case of LGMD caused by mutations in the CAPN3 gene with pseudodominant inheritance. Materials and methods. Two patients with LGMD were studied: a 59-year-old woman and her 38-year-old daughter. Clinical, genealogical and molecular genetics methods were used: limb girdle muscular dystrophy MPS panel, Sanger sequencing of DNA of the proband, her affected daughter, and six first- and second-degree relatives across four generations. Results. It was found that identical variants of the nucleotide sequence, c.598_612del and c.1746-20CG, identified in the CAPN3 gene of the proband and her daughter, are in the trans position (compound heterozygous state), causing autosomal recessive calpain-3-related LGMD. This is an example of an incredibly rare pseudodominant inheritance of an autosomal recessive disease, established through indirect evidence that the probands husband is a heterozygous carrier of a nucleotide substitution in the CAPN3 gene. Conclusion. It is crucial to examine the marriage partner for heterozygous carrier status of a gene mutation responsible for the disease in family planning and when clarifying the childs prognosis for a patient with an autosomal recessive disease. Considering the existence of a late-onset (after 30 years) LGMD phenotype associated with the CAPN3 gene, differential diagnosis should begin with testing this gene in families with late disease onset.

Novel mutations of the POLR3A gene caused POLR3-related leukodystrophy in a Chinese family: a case report

Background: POLR3-related leukodystrophy is an autosomal recessive neurodegenerative disorder characterized by onset time ranging from the neonatal period to late childhood, progressive motor decline that manifests as spasticity, ataxia, tremor, and cerebellar symptoms, as well as mild cognitive regression and hypodontia. POLR3-related leukodystrophy belongs to the family of RNA polymerase III-related leukodystrophy, which are caused by biallelic mutations in the POLR3A, POLR3B, POLRC1, or POLR3K genes. Case presentation: In this study, we report a female child with POLR3-related leukodystrophy manifesting as cognitive decline, moderate dysarthria, motor decline, cerebellar syndrome, short stature, dysphagia, hypodontia, and mild delayed myelination by brain imaging. Interestingly, polytrichia and bronchodysplasia were first observed in a POLR3-related leukodystrophy patient. Medical exome sequencing with high coverage depth was employed to identify potential genetic variants in the patient. Novel compound heterozygous mutations of the POLR3A gene, c.1771-6C>G and c.2611del (p.M871Cfs*8), were detected. One of them is an uncommon splice site mutation, and this is the first report of this mutation in a Chinese family. The father was determined to be a heterozygous carrier of the c.2611del (p.M871Cfs*8) mutation and the mother a heterozygous carrier of the c.1771-6C>G mutation. Conclusion: The patient’s newly emerged clinical features and mutations provide useful information for further exploration of genotype-phenotype correlations of POLR3-related leukodystrophy.

Mandibulofacial dysostosis with microcephaly: a syndrome to remember

Mandibulofacial dysostosis with microcephaly (MFDM) is a rare condition that causes abnormalities of the head and face. Other major extracranial malformations may also be found. The authors present a case of an MFDM in a 35 weeks newborn with antenatal growth restriction. The patient required resuscitation at birth and was diagnosed with oesophageal atresia with tracheoesophageal fistula at day 1. At physical examination he presented multiple congenital malformations including prominent forehead, plagiocephaly, low-set ears, malformed auricles, hypertelorism, downward-slanting eyes, micrognathia, everted lower lip, short neck, wide-spaced nipples and inguinal hernia. Imaging investigation showed dysplasia of the inner ear with agenesis of the vestibular–cochlear nerves and global cerebral atrophy. Analysis of the EFTUD2 gene revealed that the patient was a heterozygous carrier of a pathogenic mutation (c.831_832del[p.Lys277Asnsf*7]), which has not been previously described. This case illustrates the challenges faced in diagnosing and treating MFDM patients.

Novel mutations of POLR3A Gene caused hypomyelinating leukodystrophy type 7 (HLD7) in a Chinese family: a Case Report

Background Hypomyelinating leukodystrophy 7 (HLD7) is an autosomal recessive neurodegenerative disorder characterized by childhood onset of progressive motor decline that manifests as spasticity, ataxia, tremor, and cerebellar symptoms, as well as mild cognitive regression and hypodontia. HLD7 belongs to the family of RNA polymerase III-related leukodystrophy, which are caused by biallelic mutations in the POLR3A or POLR3B gene. Case presentation In this study, we report a female child with HLD7 manifesting as cognitive decline, moderate dysarthria, intellectual disability, cerebellar syndrome, short stature, dysphagia, hypodontia, and aberrant brain imaging. Interestingly, polytrichia and bronchodysplasia were first observed in the HLD7 patient. Medical exome sequencing with high coverage depth was employed to identify potential genetic variants in the patient. Novel compound heterozygous mutations of the POLR3A gene, c.1771-6C>G and c.2611del (p.M871Cfs*8), were detected. One of them is an uncommon splice site mutation, and this is the first report of this mutation in a Chinese family. The father was determined to be a heterozygous carrier of the c.2611del (p.M871Cfs*8) mutation and the mother a heterozygous carrier of the c.1771-6C>G mutation. Conclusion The patient’s newly emerged clinical features and mutations provide useful information for further exploration of genotype-phenotype correlations of HLD7.

Identification of two novel TPK1 gene mutations in a Chinese patient with thiamine pyrophosphokinase deficiency undergoing whole exome sequencing

Background The mutations of thiamine pyrophosphokinase-1 (TPK1) gene have been frequently studied in some patients with thiamine metabolism dysfunction syndrome-5 (THMD5), while TPK1 mutations in Chinese patients have been investigated by only homozygous. A search of the literature on the mutations in the Chinese population currently published revealed that no reports of compound heterozygous mutations were reported. Here, we report a Chinese patient with compound heterozygous TPK1 mutations who underwent magnetic resonance imaging (MRI), whole exome sequencing (WES), molecular diagnosis, bioinformatics analysis, and three-dimensional (3D) protein structure analysis. Case presentation A Chinese boy was born after an uneventful pregnancy to non-consanguineous and healthy parents. On the sixth day after his birth, the lactate level of the patient was between 8.6 mmol/L and 14.59 mmol/L in plasma (the normal level is in the range of 0.5–2.2 mmol/L). Lactate was reduced to the normal level after rehydration, acid correction, expansion, and other treatments. After 4 months, the patient presented with an acute, 3-h-long, non-induced convulsions, and was admitted to our hospital for weakness, decreased oral intake, and lethargy. Results achieved by electroencephalography (EEG), cerebrospinal fluid, and other biochemical findings were normal. A visible hemorrhagic lesion was also observed in the brain. Seizures increased significantly during infection, which was accompanied by higher lactic acid levels. MRI of the brain showed an obvious signal shadow, in which bilateral frontal and temporal parietal subarachnoid cavities were widened, and more abnormal signals were observed; therefore, further consideration of hypoxic-ischemic encephalopathy and genetic metabolic disease was taken into account. Conclusions The results of WES revealed that the patient was associated with compound heterozygous mutations NM_022445.3:c.[263G>A]; [226A>G] of TPK1. His parents were non-consanguineous; while his father was found to be a heterozygous carrier with the mutation c.[263G>A], his mother was identified as a heterozygous carrier with the mutation c.[226A>G]. The results indicated that the patient had a compound heterozygous TPK1 mutation, and this is the first reported case in China.

Prenatal diagnosis of ornithine transcarbamylase deficiency: optimizing pregnancy outcome in a woman with previous affected babies

Ornithine Transcarbamylase (OTC) deficiency is an inherited X-linked disorder which predominantly affects males. Females are usually carriers and may rarely be symptomatic. Affected individuals may present with severe life threatening disease immediately after birth. Those with variants of the disease may have late adult onset symptoms. We report a case of an asymptomatic female heterozygous carrier of the defect with recurrent poor obstetric outcomes and subsequent management with prenatal diagnostic testing.