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Case Report: Investigation and molecular genetic diagnosis of familial hypomagnesaemia.

ABSTRACT: Genetic mutations causing familial hypomagnesaemia syndromes are well-recognised. Affected patients can present with severe symptoms of hypomagnesaemia, such as seizures or cardiac arrhythmia. We report an affected child, from a consanguineous family, who presented in the first weeks of life with seizures secondary to hypomagnesaemia, without other associated clinical features. We performed whole exome sequencing in the affected child and segregation analysis within the family, which revealed a novel homozygous missense mutation in TRPM6, which was confirmed as a heterozygous allele in both parents and two younger siblings who had transient hypomagnesaemia. Using in silico modelling, we provide evidence that the missense variant p.(K1098E) in TRPM6 is pathogenic, as it disrupts stabilising TRP domain interactions. Management of familial hypomagnesaemia relies on prompt recognition, early magnesium replacement and lifelong monitoring.

SUBMITTER: Willows J

PROVIDER: S-EPMC6694456 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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Case Report: Investigation and molecular genetic diagnosis of familial hypomagnesaemia.

Willows Jamie J Al Badi Maryam M Richardson Chloe C Al Sinani Aisha A Edwards Noel N Rice Sarah S Sayer John A JA

F1000Research 20190515

Genetic mutations causing familial hypomagnesaemia syndromes are well-recognised. Affected patients can present with severe symptoms of hypomagnesaemia, such as seizures or cardiac arrhythmia. We report an affected child, from a consanguineous family, who presented in the first weeks of life with seizures secondary to hypomagnesaemia, without other associated clinical features. We performed whole exome sequencing in the affected child and segregation analysis within the family, which revealed ...[more]

PMID: 31448104

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Project description:BACKGROUND:Sixty mutations of claudin 16 coding gene have been reported in familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) patients. Recent investigations revealed that a highly conserved glycine-leucine-tryptophan (115G-L-W117) motif in the first extracellular segment (ESC1) of claudin 16 might be essential for stabilization of the appropriately folded ECS1 structure and conservation of normal claudin 16 function. However, neither missense nor nonsense mutation has ever been described in this motif. Our study aimed at identifying mutations in a Chinese patient with FHHNC and exploring the association between genotype and phenotype. CASE PRESENTATION:A 33-year-old female presented with 4 years history of recurrent acute pyelonephritis without other notable past medical history. Her healthy parents, who aged 56 and 53 respectively, were second cousins, and her only sibling died from renal failure without definite cause at age 25. Renal ultrasound imaging demonstrated atrophic kidneys and bilateral nephrocalcinosis. The laboratory workup revealed impaired renal function (Stage CKD IV), hypocalcemia and mild hypomagnesemia, accompanied with marked renal loss of magnesium and hypercalciuria. During the follow-up, treatment with calcitriol and calcium but not with magnesium was difficult to achieve normal serum calcium levels, whereas her serum magnesium concentration fluctuated within normal ranges. In the end, the patient unavoidably reached ESRD at 36 years old. The clinical features and family history suggested the diagnosis of FHHNC. To make a definite diagnosis, we use whole-exome sequencing to identify the disease-causing mutations and Sanger sequencing to confirm the mutation co-segregation in the family. As a result, a novel homozygous mutation (c.346C?>?G, p.Leu116Val) in 115G-L-W117 motif of claudin 16 was identified. Her parents, grandmother and one of her cousins carried heterozygous p.Leu116Val, whereas 200 unrelated controls did not carry this mutation. CONCLUSIONS:We described a delayed diagnosis patient with FHHNC in the Chinese population and identified a novel missense mutation in the highly conserved 115G-L-W117 motif of claudin 16 for the first time. According to the reported data and the information deduced from 3D modeling, we speculate that this mutation probably reserve partial residual function which might be related to the slight phenotype of the patient.

Dataset Information

Case Report: Investigation and molecular genetic diagnosis of familial hypomagnesaemia.

Publications

Case Report: Investigation and molecular genetic diagnosis of familial hypomagnesaemia.

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