A Rare Case of Neonatal Hypomagnesemia with Secondary Hypocalcemia Caused by a Novel Homozygous TRPM6 Gene Variant

BACKGROUND Familial hypomagnesemia with secondary hypocalcemia (HSH) is a rare autosomal recessive disorder (OMIM# 602014) caused by mutations in the gene encoding transient receptor potential melastatin 6 (TRPM6)) on chromosome 9q22, a channel involved in epithelial magnesium resorption. While a plethora of studies have delineated various clinical manifestations pertinent to this mutation, the literature is devoid of connections between TRPM6 mutations and bleeding diathesis, or sudden infant death syndrome (SIDS). This report presents a case of familial HSH associated with the novel homozygous TRPM6 gene variant c.5281C>G p. (Arg1761Gly) chr9: 77354845. CASE REPORT This report details a 26-day-old neonate, born full term with optimal Apgar scores, who experienced an abrupt emergence of apnea, cyanosis, bilateral nasal bleeding, and diminished alertness. Despite the neonate's initially unremarkable clinical birth indicators, a meticulous assessment unveiled a pronounced family history of SIDS, including a sibling previously diagnosed with hypomagnesemia. Laboratory examination of the infant demonstrated severe hypomagnesemia and hypocalcemia, conditions which were promptly ameliorated following intravenous administration of magnesium and calcium. Whole-exome sequencing identified a homozygous TRPM6 gene mutation c.5281C>G p. (Arg1761Gly) at chr9: 77354845. This gene is crucial for magnesium regulation. The mutation involves a cytosine-to-guanine shift, resulting in an arginine to glycine amino acid substitution at position 1761 of the TRPM6 protein. CONCLUSIONS This report has highlighted that infantile hypomagnesemia may be associated with symptoms and signs that can mimic infection, or it can present with seizures. Although familial HSH is a rare genetic disorder that can be identified by genetic testing, correction of hypomagnesemia is the most important and immediate clinical management strategy.

Hereditary hypomagnesemia with secondary hypocalcemia caused by a novel mutation in TRPM6 gene

OBJECTIVES

Hereditary hypomagnesemia with secondary hypocalcemia (HSH), which results from variations in the transient receptor potential melastatin 6 (TRPM6) genes, is a rare hereditary cause of extremely low serum magnesium levels. We describe an infant with triggered seizures due to hypomagnesemia and a novel mutation in TRPM6 gene was identified.

CASE PRESENTATION

A 10-month-old boy presented with multidrug resistant seizures, and axial hypotonia due to severe hypomagnesemia. Electroencephalography and neuroimaging of the patient was normal. He had a favorable outcome with magnesium supplement. In this study, the patient underwent clinical exome sequencing (CES) which detected a novel homozygous variant in the TRPM6 gene: NM_017662.5: c.5571-3C>G. After replacing his magnesium orally, he was free from seizures and had an encouraging outcome at the twelfth-month follow-up.

CONCLUSIONS

HSH often presents with developmental issues, treatment-resistant seizures, and increased neuromuscular excitability. Untreated hypomagnesemia can potentially be fatal and severely impair cognitive function. Clinical suspicion is essential for early diagnosis and treatment.

Renal diseases that course with hypomagnesemia. Comments on a new hereditary hypomagnesemic tubulopathy

Renal diseases associated with hypomagnesemia are a complex and diverse group of tubulopathies caused by mutations in genes encoding proteins that are expressed in the thick ascending limb of the loop of Henle and in the distal convoluted tubule. In this paper, we review the initial description, the clinical expressiveness and etiology of four of the first hypomagnesemic tubulopathies described: type 3 Bartter and Gitelman diseases, Autosomal recessive hypomagnesemia with secondary hypocalcemia and Familial hypomagnesemia with hypercalciuria and nephrocalcinosis. The basic biochemical patterns observed in renal tubular hypomagnesemias and the modalities of transport and interaction that occur between the transporters involved in the reabsorption of magnesium in the distal convoluted tubule are described below. Finally, the recent report of a new renal disease with hypomagnesemia, type 2 hypomagnesemia with secondary hypocalcemia caused by reduced TRPM7 channel activity is described.

A functional study for verifying the pathogenicity of a TRPM6 variant of uncertain significance: A novel non-canonical splicing-site variant in primary hypomagnesemia with secondary hypocalcemia

INTRODUCTION

Primary hypomagnesemia with secondary hypocalcemia (HSH) is a rare autosomal recessive disease caused by biallelic variants in TRPM6 gene.

METHODS

In this study, we reported a Chinese patient diagnosed with HSH in Tianjin Children's Hospital. Detailed clinical examination and laboratory test were performed and whole exome sequencing (WES) was applied to detect the pathogenic gene in the proband. The suspected compound heterozygous variant in TRPM6 gene was verified by Sanger sequencing and quantitative real-time PCR technology. Minigene assay was performed to verify the function of the variant suspected to affect splicing process.

RESULTS

The patient presented with seizure and markedly decreased levels of serum magnesium and calcium. WES combined with functional study diagnosed a pediatric patient with HSH caused by a compound heterozygous variant in TRPM6 gene, containing a novel non-canonical splicing-site variant c.5058-26A > G and a heterozygous deletion in exons 27-33 (chr9q21.13: 77357467-77376734).

CONCLUSIONS

The compound heterozygous variant in TRPM6 gene is the pathogenic cause of the proband. The combined application of WES and functional study contribute to validating the effect of an uncertain genetic variant on splicing, improving the pathogenicity evidence and identifying the etiology of the disease. It is helpful for early diagnosis and treatment of HSH.

[Familial hypomagnesaemia with secondary hypocalcaemia as a cause of seizures in children]

This case report presents a three-month-old girl, previously healthy, who was admitted to the hospital due to a cyanotic episode during breastfeeding. The episode was initially interpreted as aspiration. She had recurrent generalised seizures, and blood tests revealed hypomagnesaemia and hypocalcaemia. The electrolyte abnormalities were corrected by intravenous magnesium with subsequent normalisation of the calcium level. Genetic testing discovered a deletion in the TRPM6, which is associated with familial hypomagne-s-aemia with secondary hypocalcaemia. It is important to identify electrolyte disturbances in infants with afebrile seizures.

CNNM2 homozygous mutations cause severe refractory hypomagnesemia, epileptic encephalopathy and brain malformations

Magnesium (Mg²⁺) plays a crucial role in many biological processes especially in the brain, heart and skeletal muscle. Mg²⁺ homeostasis is regulated by intestinal absorption and renal reabsorption, involving a combination of different epithelial transport pathways. Mutations in any of these transporters result in hypomagnesemia with variable clinical presentations. Among these, CNNM2 is found along the basolateral membrane of distal tubular segments where it is involved in Mg²⁺ reabsorption. To date, heterozygous mutations in CNNM2 have been associated with a variable phenotype, ranging from isolated hypomagnesemia to intellectual disability and epilepsy. The only homozygous mutation reported so far, is responsible for hypomagnesemia associated with a severe neurological phenotype characterized by refractory epilepsy, microcephaly, severe global developmental delay and intellectual disability. Here, we report the second homozygous CNNM2 mutation (c.1642G > A,p.Val548Met) in a Moroccan patient, presenting with hypomagnesemia and severe epileptic encephalopathy. Thus, we review and discuss the phenotypic spectrum associated with CNNM2 mutations.

First report of a novel missense CLDN19 mutations causing familial hypomagnesemia with hypercalciuria and nephrocalcinosis in a Chinese family

Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC) is an autosomal recessive disorder caused by mutations in the CLDN16 or CLDN19 genes, encoding claudin-16 and claudin-19 in the thick ascending limb of Henle's loop. In patients with claudin-19 mutations, severe ocular involvement (macular coloboma, pigmentary retinitis, nystagmus, or visual loss) has been described. In this report, we presented a 12-year-old girl with rickets, polyuria, and polydipsia. She was the daughter of consanguineous parents, and she had a history of recurred hypocalcemic and hypomagnesemic tetany. On physical examination, bilateral horizontal nystagmus and severe myopia were detected. Laboratory examination revealed hypomagnesemia, hypocalcemia, hypercalciuria, nephrocalcinosis, and renal stone. A clinical diagnosis of FHHNC caused possibly by claudin-19 mutation was decided with the ocular findings. DNA analysis revealed a novel homozygous missense mutation c.241C>T in the CLDN19 gene. In conclusion, in a patient with hypomagnesemia, hypercalciuria, nephrocalcinosis, and ocular findings, a diagnosis of FHHNC caused by claudin-19 mutation should be considered. This is the first study of FHHNC in Chinese population. Our findings of the novel mutation c.241C>T in exon 2 add to the list of more than 16 mutations of CLDN19 gene reported.

Proton pump inhibitor therapy and potential long-term harm

PURPOSE OF REVIEW

This review summarizes the recent literature on the potential side-effects of proton pump inhibitors (PPIs) and known interactions with the metabolism/absorption of other drugs.

RECENT FINDINGS

Data confirm that PPIs are a very well tolerated drug class. Their high safety, efficacy and wide distribution lead to overuse, inappropriate dosage or excessive duration of treatment. Despite the absorption of micronutrients or other plausible effects on the development of bacterial infections linked to PPI-induced hypochlorhydria, it is difficult to demonstrate an association between PPI and specific symptoms. A possible negative effect of PPIs on bone integrity appears weak, but hypomagnesemia is likely a PPI drug class effect. A higher risk of Clostridium difficile infection and other infectious diseases such as small intestinal bacterial overgrowth and spontaneous bacterial peritonitis remain controversial in PPI users. However, the careful use of PPIs in cirrhotic or otherwise fragile patients is mandatory. Short-term or long-term PPI use may trigger microscopic colitis, and the management of this condition may include PPI withdrawal. The effect of PPIs on stimulating exocrine or endocrine gastric cell proliferation is poorly understood. A diagnostic delay or masking of diseases such as gastrinoma is difficult to evaluate.

SUMMARY

Short-term standard dose PPI treatment is low risk. Long-term PPI use may complicate health conditions by various mechanisms linked to PPIs and/or to hypochlorhydria.

Junctional ectopic tachycardia after congenital heart surgery

PURPOSE

In this literature review, we try to give anesthesiologists a better understanding about Junctional Ectopic Tachycardia (JET), a narrow complex tachycardia that frequently occurs during and after surgery for congenital heart disease.

SOURCE

Information was found in the databases of Pubmed, Science Direct, Medline and the Cochrane Library, by using the mesh terms "Tachycardia, Ectopic Junctional", combined with "Diagnosis", "Etiology", "Physiopathology", "Complications" and "Therapy". The publication date of the articles ranged from 1990 to 2012.

PRINCIPAL FINDINGS

Risk factors for the development JET are surgery near the AV node, a duration of cardiopulmonary bypass longer than 90 minutes, young age, the use of inotropic drugs and hypomagnesaemia. The diagnosis of Junctional Ectopic Tachycardia can be made on a 12-lead ECG, demonstrating a narrow-complex tachycardia with inverted P-waves and VA dissociation. Adenosine administration and an atrial electrocardiogram can help to confirm the diagnosis. If JET has a minimal impact on the hemodynamic status of the patient, risk factors should be avoided and the adrenergic tonus should be reduced. Hemodynamic unstable JET can be treated by amiodarone, hypothermia and pacing. Extracorporeal membrane oxygenation (ECMO) and radiofrequency or cryoablation are treatment options for life-threatening and resistant JET.

CONCLUSION

JET is the most frequent arrhythmia during and after congenital cardiac surgery. The ECG is the only available method to diagnose JET, demonstrating inverted P-waves and VA-dissociation. Amiodarone seems to be the most effective treatment option, because it can restore sinus rhythm and reduces the JET rate.

Mild hypomagnesemia as the most common Cisplatin nephropathy in Iran

INTRODUCTION

Cisplatin still has a central role in cancer chemotherapy, but is associated with the risk of toxicities, the most common of which is nephrotoxicity. The aim of the present study is evaluation of cisplatin nephrotoxicity in Iranian population of cancer patients.

MATERIALS AND METHODS

All admitted patients to the oncology service who received cisplatin were included in a prospective study from 2004 to 2010. Clinical and laboratory data including kidney function tests were recorded at baseline and during follow-up visits.

RESULTS

One hundred patients (56% men) were included. Their mean age was 44 years. Common adverse events were nausea (85%) and vomiting (78%), followed by anorexia and fatigue (20%), taste change (10%), hearing loss (8%), cramping abdominal pain (8%), and tinnitus (5%). The most important finding was normal kidney function, except for mild hypomagnesemia (grade 1 toxicity) in 18%, without any symptoms or other electrolyte abnormalities. None of the patients with hypomagnesemia had significant serum electrolyte imbalances, diarrhea, severe allergic reactions, difficulty in walking, or chest pain.

CONCLUSIONS

Cisplatin has the potential to produce both mild and severe side effects. Although the neurologic and gastrointestinal toxicities were observed, renal toxicity (rising blood urea and creatinine or electrolyte abnormality) was not observed, and the only toxicity was grade 1 hypomagnesaemia.

Novel TRPM6 mutations in familial hypomagnesemia with secondary hypocalcemia

BACKGROUND

Familial hypomagnesemia with secondary hypocalcemia (HSH) is a rare autosomal recessive disease characterized by severe hypomagnesemia and hypocalcemia associated with neurological symptoms, including generalized seizures, tetany and muscle spasms, which are refractory to anticonvulsant treatment. The pathophysiological hallmarks of HSH are the impaired intestinal absorption of magnesium accompanied by renal magnesium wasting as a result of a reabsorption defect in the distal convoluted tubule. Mutations in TRPM6, the gene encoding the transient receptor potential cation channel subfamily member 6, have been found to be responsible for this disease. In the present study, we report a Chinese family with 2 sisters affected with severe HSH, and elucidate the characteristics of TRPM6 gene mutations in these 2 patients.

METHODS

We evaluated the clinical, laboratory, and radiographic findings. All 39 TRPM6 exons and flanking exon-intron junctions from genomic DNA were amplified and sequenced in 2 affected members suffering from HSH and their family.

RESULTS

We found two novel mutations in the family, one frameshift mutation (c.1196delC) and one non-sense mutation (c.4577G>A). These mutations were predicted to result in a complete loss of function of TRPM6. Both of the sisters were compound heterozygotes for these mutations.

CONCLUSION

Our results suggested that the compound heterozygous mutations in TRPM6 were responsible for HSH in the Chinese family.

[Congenital hypomagnesemia]

MORE PRECISE IDENTIFICATION: The progress in molecular genetics has led to better understanding of primitive magnesium deficiency. Transporters of this cation have been identified in the intestines and kidneys. The majority of congential hypomanesemia phenotypes have been correlated with a defect in magnesium transport. The primary deficiency of intestinal absorption of magnesium is responsible for hypomagnesemia and subsequent hypocalcemia. DEPENDING ON THE MECHANISM: Magnesium absorption defects in Henle's loop induce hypomagnesemia with hypercalciuria and nephrocalcinosis, autosomal dominant hypocalcemia or Bartter syndrome. In isolated dominant hypomagnesemia and Gitelman syndrome, an abnormality in the distal convoluted tubule explains the primitive hypomagnesemia, through renal leaking. Conversely, the mechanisms of recessive isolated hypomagnesemia remains unknown. ORIENTING GENETIC DIAGNOSIS: In a context of primitive hypomagnesemia, the clinical and biological presentation will orient genetic research leading to correct diagnosis. However, there are many border-line phenotypes and the pheno-genotype correlation is still imperfect.

Gestational diabetes and its impact on the neonate

Gestational diabetes mellitus is a relatively common medical condition that was described as early as the nineteenth century. This article discusses the maternal and fetal pathophysiology and the impact of the maternal condition on the neonate. Fetal macrosomia and infant respiratory distress syndrome, cardiomyopathy, hypoglycemia, hypocalcemia, hypomagnesemia, polycythemia, and hyperviscosity all can occur as a result of maternal hyperglycemia and are discussed in detail. Therapeutic approaches and treatment options for the mother, manifestations and diagnosis of the infant, and current research related to this condition are also included.

Isolated magnesium malabsorption in a 10-year-old boy

Isolated magnesium malabsorption (congenital hypomagnesemia) has been reported in approximately 30 patients worldwide. Patients typically present by 6 months of age with convulsions and diarrhea. We report an unusual case of isolated magnesium malabsorption in an older boy with no diarrhea.

Primary infantile hypomagnesaemia: report of two cases

OBJECTIVE

To present case reports of two siblings with primary hypomagnesaemia both presenting with seizures, and one also with a cardiac arrhythmia. To briefly review the pathophysiology, clinical features, diagnosis, management and genetics of this disorder.

METHODOLOGY

Published literature reports of primary hypomagnesaemia and studies of hypomagnesaemia in humans. Reports of the clinical features and inheritance of primary hypomagnesaemia.

RESULTS

The information is descriptive of the pathophysiology, clinical features, diagnostic criteria, and management. Considered modes of inheritance are presented. Two cases of primary hypomagnesaemia in brothers of consanguineous parents are described. Cardiac arrhythmia at presentation has not previously been reported. Diagnosis and adequate magnesium supplementation controls the biochemical disorder and the neurological development is normal.

CONCLUSIONS

Primary hypomagnesaemia should be considered in infants with seizures, as failure to identify this metabolic disorder can result in death. Subsequent siblings, particularly male, should be closely monitored.

Reversible hypocalciuria with marginal hypercalcaemia in renal magnesium wasting

Low urinary calcium levels and hypomagnesaemia were observed in three subjects with renal tubular abnormalities. The first, with severe hypomagnesaemia due to congenital renal magnesium wasting, had mildly raised serum ionized calcium levels (1.34-1.36 mmol/l). The other two, a brother and sister, had features of Bartter's syndrome with hypokalaemia, mild hypomagnesaemia and hyperreninaemia with normal serum ionized calcium levels. Hypocalciuria was seen in 24-h urine collections and in 2-hourly timed urine collections. Magnesium loading with intramuscular MgSO4 was used to raise serum Mg to within the normal range. Tubular reabsorption of Mg (TMg) rose while TCa fell, with a rise in fractional excretion of ionized Ca and a small drop in serum ionized Ca. Serum parathyroid hormone levels rose or remained constant. This pattern is consistent with a shared Ca/Mg reabsorptive pathway with a rise in TCa when TMg is low, returning to normal when TMg is raised by Mg loading. In one subject, this imbalance was associated with marginal hypercalcaemia. The site for this pathway is likely to be the thick ascending limb of the loop of Henle.