Summary

Distinguishing primary hyperparathyroidism (PHPT) from familial hypocalciuric hypercalcaemia (FHH) can be challenging. Currently, 24-h urinary calcium is used to differentiate between the two conditions in vitamin D replete patients, with urinary calcium creatinine clearance ratio (UCCR) <0.01 suggestive of FHH and >0.02 supportive of PHPT. A 26-year-old Caucasian gentleman presented with recurrent mild hypercalcaemia and inappropriately normal parathyroid hormone (PTH) following previous parathyroidectomy 3 years prior. He had symptoms of fatigue and light-headedness. He did not have any other symptoms of hypercalcaemia. His previous evaluation appeared to be consistent with PHPT as evidenced by hypercalcaemia with inappropriately normal PTH and UCCR of 0.0118 (borderline low using guidelines of >0.01 consistent with PHPT). He underwent parathyroidectomy and three parathyroid glands were removed. His calcium briefly normalised after surgery, but rose again to pre-surgery levels within 3 months. Subsequently, he presented to our centre and repeated investigations showed 24-h urinary calcium of 4.6 mmol/day and UCCR of 0.0081 which prompted assessment for FHH. His calcium-sensing receptor (CASR) gene was sequenced and a rare inactivating variant was detected. This variant was described once previously in the literature. His mother was also confirmed to have mild hypercalcaemia with hypocalciuria and, on further enquiry, had the same CASR variant. The CASR variant was classified as likely pathogenic and is consistent with the diagnosis of FHH. This case highlights the challenges in differentiating FHH from PHPT. Accurate diagnosis is vital to prevent unnecessary surgical intervention in the FHH population and is not always straightforward.

Learning points:

• Distinguishing FHH from PHPT with co-existing vitamin D deficiency is difficult as this can mimic FHH. Therefore, ensure patients are vitamin D replete prior to performing 24-h urinary calcium collection.

• Individuals with borderline UCCR could have either FHH or PHPT. Consider performing CASR gene sequencing for UCCR between 0.01 and 0.02.

• Parathyroid imaging is not required for making the diagnosis of PHPT. It is performed when surgery is considered after confirming the diagnosis of PHPT.

Summary

A patient with atypical partial lipodystrophy who had a transient initial response to metreleptin experienced acute worsening of her metabolic state when neutralizing antibodies against metreleptin appeared. Because her metabolic status continued to deteriorate, a therapeutic trial with melanocortin-4 receptor agonist setmelanotide, that is believed to function downstream from leptin receptor in the leptin signaling system, was undertaken in an effort to improve her metabolic status for the first time in a patient with lipodystrophy. To achieve this, a compassionate use (investigational new drug application; IND) was initiated (NCT03262610). Glucose control, body fat by dual-energy X-ray absorptiometry and MRI, and liver fat by proton density fat fraction were monitored. Daily hunger scores were assessed by patient filled questionnaires. Although there was a slight decrease in hunger scales and visceral fat, stimulating melanocortin-4 receptor by setmelanotide did not result in any other metabolic benefit such as improvement of hypertriglyceridemia or diabetes control as desired. Targeting melanocortin-4 receptor to regulate energy metabolism in this setting was not sufficient to obtain a significant metabolic benefit. However, complex features of our case make it difficult to generalize these observations to all cases of lipodystrophy. It is still possible that melanocortin-4 receptor agonistic action may offer some therapeutic benefits in leptin-deficient patients.

Learning points:

• A patient with atypical lipodystrophy with an initial benefit with metreleptin therapy developed neutralizing antibodies to metreleptin (Nab-leptin), which led to substantial worsening in metabolic control. The neutralizing activity in her serum persisted for longer than 3 years.

• Whether the worsening in her metabolic state was truly caused by the development of Nab-leptin cannot be fully ascertained, but there was a temporal relationship. The experience noted in our patient at least raises the possibility for concern for substantial metabolic worsening upon emergence and persistence of Nab-leptin. Further studies of cases where Nab-leptin is detected and better assay systems to detect and characterize Nab-leptin are needed.

• The use of setmelanotide, a selective MC4R agonist targeting specific neurons downstream from the leptin receptor activation, was not effective in restoring metabolic control in this complex patient with presumed diminished leptin action due to Nab-leptin.

• Although stimulating the MC4R pathway was not sufficient to obtain a significant metabolic benefit in lowering triglycerides and helping with her insulin resistance as was noted with metreleptin earlier, there was a mild reduction in reported food intake and appetite.

• Complex features of our case make it difficult to generalize our observation to all leptin-deficient patients. It is possible that some leptin-deficient patients (especially those who need primarily control of food intake) may still theoretically benefit from MC4R agonistic action, and further studies in carefully selected patients may help to tease out the differential pathways of metabolic regulation by the complex network of leptin signaling system.

Summary

A 19-year-old female presented at 25-weeks gestation with pancreatitis. She was found to have significant hypertriglyceridaemia in context of an unconfirmed history of familial hypertriglyceridaemia. This was initially managed with fasting and insulin infusion and she was commenced on conventional interventions to lower triglycerides, including a fat-restricted diet, heparin, marine oil and gemfibrozil. Despite these measures, the triglyceride levels continued to increase as she progressed through the pregnancy, and it was postulated that she had an underlying lipoprotein lipase defect. Therefore, a multidisciplinary decision was made to commence therapeutic plasma exchange to prevent further episodes of pancreatitis. She underwent a total of 13 sessions of plasma exchange, and labour was induced at 37-weeks gestation in which a healthy female infant was delivered. There was a rapid and significant reduction in triglycerides in the 48 h post-delivery. Subsequent genetic testing of hypertriglyceridaemia genes revealed a missense mutation of the LPL gene. Fenofibrate and rosuvastatin was commenced to manage her hypertriglyceridaemia postpartum and the importance of preconception counselling for future pregnancies was discussed. Hormonal changes in pregnancy lead to an overall increase in plasma lipids to ensure adequate nutrient delivery to the fetus. These physiological changes become problematic, where a genetic abnormality in lipid metabolism exists and severe complications such as pancreatitis can arise. Available therapies for gestational hypertriglyceridaemia rely on augmentation of LPL activity. Where there is an underlying LPL defect, these therapies are ineffective and removal of triglyceride-rich lipoproteins via plasma exchange should be considered.

Learning points:

• Hormonal changes in pregnancy, mediated by progesterone,oestrogen and human placental lactogen, lead to a two- to three-fold increase in serum triglyceride levels.

• Pharmacological intervention for management of gestational hypertriglyceridaemia rely on the augmentation of lipoprotein lipase (LPL) activity to enhance catabolism of triglyceride-rich lipoproteins.

• Genetic mutations affecting the LPL gene can lead to severe hypertriglyceridaemia.

• Therapeutic plasma exchange (TPE) is an effective intervention for the management of severe gestational hypertriglyceridaemia and should be considered in cases where there is an underlying LPL defect.

• Preconception counselling and discussion regarding contraception is of paramount importance in women with familial hypertriglyceridaemia.

Summary

We report the renal histology of a 66-year-old man with hypertension, cardiovascular disease, and a 30-year history of type 2 diabetes mellitus with proliferative diabetic retinopathy, diabetic neuropathy, and diabetic foot status post toe amputation. Urinary protein excretion was 1.4 g/gCr, serum creatinine level 0.86 mg/dL, estimated glomerular filtration rate 69 mL/min/1.73 m², and HbA1c 13–15%, despite using insulin. Light microscopy showed global glomerulosclerosis in 37% of the glomeruli, but the remaining glomeruli were intact. Significant polar vasculosis was present, while arteriolar sclerosis was mild. Electron microscopy revealed a thickened glomerular basement membrane, which is compatible with the early stage of diabetic glomerulopathy. The presented case was unique because glomerular changes seen typically in diabetes were not seen in the patient, despite the long-standing history of diabetes and diabetic comorbidities, while prominent polar vasculosis was found. Polar vascular formation helps preserve the glomeruli by allowing hyperosmotic blood bypass the glomeruli; this decreases intraglomerular pressure and minimizes glomerular endothelial damage.

Learning points:

• A 66-year-old man with a 30-year history of type 2 diabetes mellitus with poor glycemic control underwent renal biopsy, which showed scarce glomerular changes typically seen in diabetic kidney disease and instead revealed significant polar vasculosis.

• Past studies demonstrated that the increased small vessels around the vascular hilus in diabetic patients originated from the afferent arterioles and drained into the peritubular capillaries.

• Polar vascular formation may preserve glomerular function by allowing the blood flow to bypass the glomeruli and decreasing the intraglomerular pressure, which minimizes endothelial damage of the glomerular tufts.

Summary

Diabetic myonecrosis, also known as diabetic muscle infarction is a rare complication of diabetes mellitus usually associated with longstanding suboptimal glycaemic control. Although theories of atherosclerosis, diabetic microangiopathy, vasculitis, ischaemia-reperfusion injury and hypercoagulable state have been proposed to explain the pathophysiology, none of these have been able to individually explain the pathophysiology in entirety. Diabetic renal disease is the most common risk factor for developing DMN and its recurrence. The diagnosis is often missed due to lack of awareness and the presentation mimicking other conditions associated with DM. The routine laboratory investigations are often non-specific and do not provide much value in the diagnosis as well. Muscle biopsy can provide a definite diagnosis but is not currently recommended due to its invasiveness and association with prolonged time to symptoms resolution. Magnetic resonance imaging, in combination with classic history and risk factors can clinch the diagnosis. Treatment is generally analgesia and rest, although the former’s use may be limited in the presence of renal disease.

Learning points:

• Diabetic myonecrosis is a rare complication of diabetes mellitus associated with longstanding suboptimal glycaemic control.

• Diabetic renal disease is a known risk factor, although the evidence is merely observational.

• Although muscle biopsy could provide a definite diagnosis, it is not recommended as it can prolong the disease process and should be reserved only for cases not responding to conventional treatment.

• Typical MRI findings in combination with classic symptoms and risk factors can clinch the diagnosis

• Current treatment recommendations include NSAIDs and/or aspirin (if not contraindicated) alongside bed rest. Physiotherapy is not recommended in the acute phase but should be started as soon as patient is discharged from hospital.

• Optimal glycaemic control is key to prevent recurrence.

Learning points:

• Clinicians prescribing ferric carboxymaltose (Ferinject^®) should be aware of the common side effect of hypophosphataemia, which could be mild, moderate or severe.

• Patients receiving iron infusion should be educated concerning this potential side effect.

• Pre-existing vitamin D deficiency, low calcium levels, low phosphate levels or raised parathyroid hormone levels may be risk factors, and these should be evaluated and corrected before administering intravenous iron.

• Patients may require phosphate and vitamin D replacement along with monitoring for a long period after iron infusion-induced hypophosphataemia.

• Every incident should be reported to the designated body so that the true prevalence and management thereof can be ascertained.

Learning points:

• High glycemic variability is frequent in patients operated with gastric bypass.

• Diverse eating patterns, such as prolonged fasting and simple carbohydrate ingestion, and mental health disorders, including anxiety, can promote and be confused with worsened hypoglycemia.

• CGM requires a detailed record of food ingested that can be accompanied by associated factors (circumstances, eating patterns, emotional symptoms). This allows the detection of particular behaviors and amount of dietary simple carbohydrates to guide recommendations provided within clinical care of these patients.

Learning points:

• Hypertriglyceridemia-induced acute pancreatitis has significant morbidity and mortality, and prompt treatment is imperative.

• When no secondary causes are readily identified, genetic evaluation should be pursued in hypertriglyceridemia in children.

• Intravenous insulin is a safe and effective acute treatment for hypertriglyceridemia in children, even in infants.

• Long-term management with dietary modifications alone could be effective for primary hypertriglyceridemia due to lipoprotein lipase deficiency, at least in early childhood phase.

Learning points:

• Tumour expansion may occur in acromegaly during pregnancy.

• Treatment options for tumour expansion in pregnancy include both medical and surgical options.

• Somatostatin analogues may be a viable medical alternative to surgery in patients with tumour expansion during pregnancy.

Learning points:

• Primary hyperparathyroidism in pregnancy is associated with a high incidence of associated maternal fetal and neonatal complications directly proportionate to degree of maternal serum calcium levels.

• Parathyroidectomy is the definitive treatment for primary hyperparathyroidism in pregnancy and was used in the management of all three cases in this series. It is recommended when serum calcium is persistently greater than 2.75 mmol/L and or for the management of maternal or fetal complications of hypercalcaemia. Surgical management, when necessary is ideally performed in the second trimester.

• Primary hyperparathyroidism is genetically determined in ~10% of cases, where the likelihood is increased in those under 40 years, where there is relevant family history and those with other related endocrinopathies. Genetic testing is a useful diagnostic adjunct and can guide treatment and management options for patients diagnosed with primary hyperparathyroidism in pregnancy, as described in case 1 in this series, who was diagnosed with MEN1 syndrome.

• Women of reproductive age with primary hyperparathyroidism need to be informed of the risks and complications associated with primary hyperparathyroidism in pregnancy and pregnancy should be deferred and or avoided until curative surgery has been performed and calcium levels have normalised.