Diagnosis and Treatment > Signs and Symptoms > Hypomagnesaemia
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Summary
Familial hypomagnesemia with secondary hypocalcemia (FHSH) is a rare autosomal recessive disorder (OMIM# 602014) characterized by profound hypomagnesemia associated with hypocalcemia. It is caused by mutations in the gene encoding transient receptor potential cation channel member 6 (TRPM6). It usually presents with neurological symptoms in the first months of life. We report a case of a neonate presenting with recurrent seizures and severe hypomagnesemia. The genetic testing revealed a novel variant in the TRPM6 gene. The patient has been treated with high-dose magnesium supplementation, remaining asymptomatic and without neurological sequelae until adulthood. Early diagnosis and treatment are important to prevent irreversible neurological damage.
Learning points:
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Loss-of-function mutations of TRPM6 are associated with FHSH.
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FHSH should be considered in any child with refractory hypocalcemic seizures, especially in cases with serum magnesium levels as low as 0.2 mM.
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Normocalcemia and relief of clinical symptoms can be assured by administration of high doses of magnesium.
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Untreated, the disorder may be fatal or may result in irreversible neurological damage.
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Starship Children’s Health, Auckland District Health Board, Auckland, New Zealand
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Starship Children’s Health, Auckland District Health Board, Auckland, New Zealand
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Summary
Adrenocortical carcinoma (ACC) during childhood is a rare malignant tumor that frequently results in glucocorticoid and/or androgen excess. When there are signs of microscopic or macroscopic residual disease, adjuvant therapy is recommended with mitotane, an adrenolytic and cytotoxic drug. In addition to the anticipated side effect of adrenal insufficiency, mitotane is known to cause gynecomastia and hypothyroidism in adults. It has never been reported to cause precocious puberty. A 4-year-old girl presented with a 6-week history of virilization and elevated androgen levels and 1-year advancement in bone age. Imaging revealed a right adrenal mass, which was subsequently surgically excised. Histology revealed ACC with multiple unfavorable features, including high mitotic index, capsular invasion and atypical mitoses. Adjuvant chemotherapy was started with mitotane, cisplatin, etoposide and doxorubicin. She experienced severe gastrointestinal side effects and symptomatic adrenal insufficiency, which occurred despite physiological-dose corticosteroid replacement. She also developed hypothyroidism that responded to treatment with levothyroxine and peripheral precocious puberty (PPP) with progressive breast development and rapidly advancing bone age. Five months after discontinuing mitotane, her adrenal insufficiency persisted and she developed secondary central precocious puberty (CPP). This case demonstrates the diverse endocrine complications associated with mitotane therapy, which contrast with the presentation of ACC itself. It also provides the first evidence that the known estrogenic effect of mitotane can manifest as PPP.
Learning points:
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Adrenocortical carcinoma is an important differential diagnosis for virilization in young children
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Mitotane is a chemotherapeutic agent that is used to treat adrenocortical carcinoma and causes adrenal necrosis
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Mitotane is an endocrine disruptor. In addition to the intended effect of adrenal insufficiency, it can cause hypothyroidism, with gynecomastia also reported in adults.
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Patients taking mitotane require very high doses of hydrocortisone replacement therapy because mitotane interferes with steroid metabolism. This effect persists after mitotane therapy is completed
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In our case, mitotane caused peripheral precocious puberty, possibly through its estrogenic effect.
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Summary
29-year-old female presenting with an 8-year history of unexplained hypomagnesaemia, which was severe enough to warrant intermittent inpatient admission for intravenous magnesium. Urinary magnesium was inappropriately normal in the context of hypomagnesaemia indicating magnesium wasting. Ultrasound imaging demonstrated unilateral renal cysts and computed tomography of kidneys, ureters and bladder showed a bicornuate uterus. Referral to genetic services and subsequent testing revealed a de novo HNF1B deletion.
Learning points:
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HNF1B loss-of-function mutations are one of the most common monogenic causes of congenital anomalies of the kidney and urinary tract.
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Those with HNF1B mutations may have some of a constellation of features (renal and hepatic cysts, deranged liver function tests, maturity onset diabetes of the young type 5 (MODY5), bicornuate uterus, hyperparathyroidism, hyperuricaemic gout, but presenting features are highly heterogeneous amongst patients and no genotype/phenotype correlation exists.
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HNF1B mutations are inherited in an autosomal dominant pattern but up to 50% of cases are de novo.
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HNF1B mutations can be part of the Chr17q12 deletion syndrome, a contiguous gene deletion syndrome.
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Inorganic oral magnesium replacements are generally poorly tolerated with side effects of diarrhoea. Organic magnesium compounds, such as magnesium aspartate, are better absorbed oral replacement therapies.
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Summary
We describe severe hypokalaemia and hypertension due to a mineralocorticoid effect in a patient with myelodysplastic syndrome taking posaconazole as antifungal prophylaxis. Two distinct mechanisms due to posaconazole are identified: inhibition of 11β hydroxylase leading to the accumulation of the mineralocorticoid hormone 11-deoxycorticosterone (DOC) and secondly, inhibition of 11β hydroxysteroid dehydrogenase type 2 (11βHSD2), as demonstrated by an elevated serum cortisol-to-cortisone ratio. The effects were ameliorated by spironolactone. We also suggest that posaconazole may cause cortisol insufficiency. Patients taking posaconazole should therefore be monitored for hypokalaemia, hypertension and symptoms of hypocortisolaemia, at the onset of treatment and on a monthly basis. Treatment with mineralocorticoid antagonists (spironolactone or eplerenone), supplementation of glucocorticoids (e.g. hydrocortisone) or dose reduction or cessation of posaconazole should all be considered as management strategies.
Learning points:
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Combined hypertension and hypokalaemia are suggestive of mineralocorticoid excess; further investigation is appropriate.
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If serum aldosterone is suppressed, then further investigation to assess for an alternative mineralocorticoid is appropriate, potentially using urine steroid profiling and/or serum steroid panelling.
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Posaconazole can cause both hypokalaemia and hypertension, and we propose that this is due to two mechanisms – both 11β hydroxylase inhibition and 11β HSD2 inhibition.
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Posaconazole treatment may lead to cortisol insufficiency, which may require treatment; however, in this clinical case, the effect was mild.
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First-line treatment of this presentation would likely be use of a mineralocorticoid antagonist.
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Patients taking posaconazole should be monitored for hypertension and hypokalaemia on initiation and monthly thereafter.
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Search for other papers by Cristina Lamas in
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Summary
Mutations in hepatocyte nuclear factor 1β gene (HNF1B) are responsible for a multisystemic syndrome where monogenic diabetes (classically known as MODY 5) and renal anomalies, mostly cysts, are the most characteristic findings. Urogenital malformations, altered liver function tests, hypomagnesemia or hyperuricemia and gout are also part of the syndrome. Diabetes in these patients usually requires early insulinization. We present the case of a young non-obese male patient with a personal history of renal multicystic dysplasia and a debut of diabetes during adolescence with simple hyperglycemia, negative pancreatic autoimmunity and detectable C-peptide levels. He also presented epididymal and seminal vesicle cysts, hypertransaminasemia, hyperuricemia and low magnesium levels. In the light of these facts we considered the possibility of a HNF1B mutation. The sequencing study of this gene confirmed a heterozygous mutation leading to a truncated and less functional protein. Genetic studies of his relatives were negative; consequently, it was classified as a de novo mutation. In particular, our patient maintained good control of his diabetes on oral antidiabetic agents for a long period of time. He eventually needed insulinization although oral therapy was continued alongside, allowing reduction of prandial insulin requirements. The real prevalence of mutations in HNF1B is probably underestimated owing to a wide phenotypical variability. As endocrinologists, we should consider this possibility in young non-obese diabetic patients with a history of chronic non-diabetic nephropathy, especially in the presence of some of the other characteristic manifestations.
Learning points:
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HNF1B mutations are a rare cause of monogenic diabetes, often being a part of a multisystemic syndrome.
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The combination of young-onset diabetes and genitourinary anomalies with slowly progressive nephropathy of non-diabetic origin in non-obese subjects should rise the suspicion of such occurrence. A family history may not be present.
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Once diagnosis is made, treatment of diabetes with oral agents is worth trying, since the response can be sustained for a longer period than the one usually described. Oral treatment can help postpone insulinization and, once this is necessary, can help reduce the required doses.
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Summary
A 33-year-old male was diagnosed with a metastatic neuroendocrine carcinoma of uncertain primary. He defaulted from follow-up without therapy and some months later developed episodic severe hypoglycaemia, which was found to be associated with inappropriately elevated insulin and C-peptide levels. It was considered likely that the neuroendocrine tumour was the source of the insulin secretion. Diazoxide and somatostatin analogue were used to control hypoglycaemia. Much later in the course of the disease, he developed metabolic derangement, increased skin pigmentation and psychological disturbance, without frankly Cushingoid physical findings. Investigations revealed highly elevated cortisol levels (the levels having previously been normal) with markedly raised ACTH levels, consistent with the co-secretion of ACTH and insulin by the tumour. Treatment with metyrapone improved his psychological state and electrolyte imbalance. Unfortunately, despite several cycles of first-, second- and third-line chemotherapy from the start of the first hormonal presentation onwards, imaging revealed widespread progressive metastatic disease and the patient eventually passed away. This case highlights the importance of keeping in mind the biochemical heterogeneity of endocrine tumours during their treatment.
Learning points
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The clinical presentation of insulin-secreting tumours includes symptoms of neuroglycopaenia and sympathetic overstimulation.
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Tumour-associated hypoglycaemia can be due to pancreatic insulinomas, and although ectopic hormone production occurs in a number of tumours, ectopic secretion of insulin is rare.
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A possible switch in the type of hormone produced can occur during the growth and progression of neuroendocrine tumours and, when treating neuroendocrine tumours, it is important to keep in mind their biochemical heterogeneity.
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Summary
Hypokalaemia may present as muscle cramps and Cardiac arrhythmias. This is a condition commonly encountered by endocrinologists and general physicians alike. Herein, we report the case of a 43-year-old gentleman admitted with hypokalaemia, who following subsequent investigations was found to have Gitelman's syndrome (GS). This rare, inherited, autosomal recessive renal tubular disorder is associated with genetic mutations in the thiazide-sensitive sodium chloride co-transporter and magnesium channels in the distal convoluted tubule. Patients with GS typically presents at an older age, and a spectrum of clinical presentations exists, from being asymptomatic to predominant muscular symptoms. Clinical suspicion should be raised in those with hypokalaemic metabolic alkalosis associated with hypomagnesaemia. Treatment of GS consists of long-term potassium and magnesium salt replacement. In general, the long-term prognosis in terms of preserved renal function and life expectancy is excellent. Herein, we discuss the biochemical imbalance in the aetiology of GS, and the case report highlights the need for further investigations in patients with recurrent hypokalaemic episodes.
Learning points
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Recurrent hypokalaemia with no obvious cause warrants investigation for hereditary renal tubulopathies.
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GS is the most common inherited renal tubulopathy with a prevalence of 25 per million people.
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GS typically presents at an older age and clinical suspicion should be raised in those with hypokalaemic metabolic alkalosis associated with hypomagnesaemia.
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Confirmation of diagnosis is by molecular analysis for mutation in the SLC12A3 gene.
