Pseudo-pheochromocytoma due to obstructive sleep apnea: a case report

SUMMARY

Obstructive sleep apnea (OSA) is a condition of intermittent nocturnal upper airway obstruction. OSA increases sympathetic drive which may result in clinical and biochemical features suggestive of pheochromocytoma. We present the case of a 65-year-old male with a 2.9-cm left adrenal incidentaloma on CT, hypertension, symptoms of headache, anxiety and diaphoresis, and persistently elevated 24-h urine norepinephrine (initially 818 nmol/day (89-470)) and normetanephrine (initially 11.2 µmol/day (0.6-2.7)). He was started on prazosin and underwent left adrenalectomy. Pathology revealed an adrenal corticoadenoma with no evidence of pheochromocytoma. Over the next 2 years, urine norepinephrine and normetanephrine remained significantly elevated with no MIBG avid disease. Years later, he was diagnosed with severe OSA and treated with continuous positive airway pressure. Urine testing done once OSA was well controlled revealed complete normalization of urine norepinephrine and normetanephrine with substantial symptom improvement. It was concluded that the patient never had a pheochromocytoma but rather an adrenal adenoma with biochemistry and symptoms suggestive of pheochromocytoma due to untreated severe OSA. Pseudo-pheochromocytoma is a rare presentation of OSA and should be considered on the differential of elevated urine catecholamines and metanephrines in the right clinical setting.

LEARNING POINTS

Obstructive sleep apnea (OSA) is a common condition among adults. OSA may rarely present as pseudo-pheochromocytoma with symptoms of pallor, palpitations, perspiration, headache, or anxiety. OSA should be considered on the differential of elevated urine catecholamines and metanephrines, especially in patients with negative metaiodobenzylguanidine (MIBG) scan results.

[Methanaphylaxis of urolithiasis. Part 3. The factors associated with increase in incidence of urinary stone disease. Current views on the mechanisms of stone formation]

All theories of stone formation are based on the common condition, which is the supersaturation of stone-forming elements. The microelements involved in the stone formation, the most common metabolic disorders and their role in stone formation are discussed.

Metabolic disturbances and renal stone promotion on treatment with topiramate: a systematic review

AIMS

The use of topiramate, which is prescribed for the management of epilepsy, for migraine headache prophylaxis and as a weight-loss agent, has been associated with the development of metabolic acidosis, hypokalaemia and renal stone disease. We systematically reviewed all the literature.

METHODS

The systematic review of the literature was realized using the principles underlying the UK Economic and Social Research Council guidance on the conduct of narrative synthesis and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement.

RESULTS

Fourty-seven reports published between 1996 and 2013 were retained for the final analysis. Five case-control studies and six longitudinal studies addressed the effect of topiramate on acid-base and potassium balance. A significant tendency towards mild-to-moderate hyperchloraemic metabolic acidosis (with bicarbonate ≤21.0 mmol l(-1) in approximately every third case) and mild hypokalaemia (with potassium ≤3.5 mmol l(-1) in 10% of the cases) was noted on treatment with topiramate, which was similar in children and adults. A single study observed that topiramate causes mild hyperuricaemia in male adults. A tendency towards hypocitraturia, a recognized promoter of renal stone formation, was noted in all patients on topiramate.

CONCLUSIONS

Increasing evidence supports the use of topiramate. Topiramate is generally well tolerated, and serious adverse events are rare. Nonetheless, the present systematic review of the literature indicates that its use is linked with the development of acidosis, hypokalaemia, hyperuricaemia and hypocitraturia.

Urinary citrate excretion in healthy children depends on age and gender

BACKGROUND

Hypocitraturia is considered a major risk factor for calcium stone formation. However, there is no widely accepted reference database of urinary citrate excretion in children. The aim of our study was to determine the amount of citrate eliminated in the urine over a 24-h period in a pediatric cohort and to determine an optimal unit reflecting excretion.

METHODS

The study cohort comprised 2,334 healthy boys and girls aged 2-18 years. The levels of urinary citrate were assessed by an enzymatic method in 24-hour urine and expressed in absolute values, as urinary concentration, citrate/creatinine ratio, per kilogram of body weight, in relation to 1.73 m2, and as the calcium/citrate index.

RESULTS

Similar incremental age-related citraturia rates were observed in both male and female subjects until puberty during which time citrate excretion became significantly higher in girls. Urinary citrate adjusted for creatinine and for body weight showed a significantly decreasing trend with increasing age in both sexes. Urinary citrate corrected for body surface was weakly correlated with age. Thus, the assumption of 180 mg/1.73 m2/24 h for males and 250 mg/1.73 m2/24 h for females as lower cut-off values appeared to be reliable from a practical perspective.

CONCLUSIONS

We found distinct sex-dependent differences in citraturia at the start of puberty, with significantly higher values of urinary citrate in girls than in boys. Further prospective studies are warranted to elucidate whether this difference represents a differentiated risk of urolithiasis.

Correspondence between Ca²⁺ and calciuria, citrate level and pH of urine in pediatric urolithiasis

BACKGROUND

Hypercalciuria and hypocitraturia are considered the most important risk factors for urolithiasis. Citrate binds to urinary calcium to form a soluble complex which decreases the availability of ionized calcium (Ca(2+)) necessary for calcium oxalate formation and phosphate crystallization. The aims of this study were to assess the Ca(2+) fraction in relation to total calciuria, citraturia and urinary pH and to determine whether urinary Ca(2+) concentration is a helpful biomarker in metabolic evaluation of children with urolithiasis.

METHODS

We collected 24-h urine samples from 123 stone-forming children and adolescents with hypocitraturia and from 424 healthy controls. Total calciuria (total calcium, Catotal), Ca(2+), pH, citrate, oxalate and Bonn Risk Index (BRI) were assessed and compared between the two groups.

RESULTS

Total calciuria and Ca(2+) content were higher in stone-formers than in the healthy children. In both stone-formers and controls, Ca(2+) content was inversely related to citraturia and urinary pH, whereas the Ca(2+)/Catotal ratio differed slightly between the groups. A large variability in Ca(2+) level was found across individuals in both groups. The BRI increased with increasing calciuria and urine acidity.

CONCLUSIONS

Compared to controls, stone-formers with hypocitraturia demonstrated a higher urinary Ca(2+) concentration, but this was proportional to calciuria. The large individual variability in urinary Ca(2+) content limits its practical use in metabolic evaluation of children with urolithiasis. However, the Ca/Citrate ratio may be a useful clinical tool in evaluating children with urolithiasis.