A 42-year old white male 8 days post bone marrow transplantation on treatment with FK506 (tacrolimus), among many other medications, is diagnosed with a type IV renal tubular acidosis. Which one of the following features would not be compatible with this diagnosis:
Answer to Sep 16 Electrolyte Quiz is A. Perform a 24 hour urine collection for calcium (case provided by Dr. Alan Yu)
A 59 year old white female presents with a 1 week history of constipation, nausea, polyuria, and polydipsia. She says that she has been consuming cod liver oil after seeing it recommended on a recent health program on television. The patient also reported chronic cough productive of mucoid sputum, unchanged for the preceding 6 years except for one recent episode of slight hemoptysis. She denies use of antacids, weight loss, has not been immobilized, and there is no family history of hypercalcemia or endocrinopathy. Her baseline renal function was normal. Medications: hydrochlorthiazide 50 mg/day for essential hypertension. Examination was unremarkable except for dry mucous membranes. Vital signs: blood pressure 122/78 mmHg, heart rate 92 beats/minute, respiratory rate 14 breaths/minute. Laboratory data shows: Sodium 131 mEq/L, potassium 3.1 mEq/L, Chloride 95 mEq/L, CO2 32 mEq/L, Glucose 108 mg/dL, BUN 29 mg/dL, Cr 1.9 mg/dL, Alb 3.8g/dL, Calcium 17.2 mg/dL and PO4 2.3 mg/dL. Her iPTH is 291 pg/ml (10-65), 25-vitamin D 23 pg/ml (9-43), 1,25-vitamin D 30 pg/ml (15-60), TSH is normal. Her SPEP/UPEP show no monoclonal bands. A skeletal survey is negative and a chest X-ray and chest CT scan are both negative.
Explanation:
There are important clues from the history: the history already reveals use of cod liver oil (vitamin A and D), thiazides, and respiratory symptoms (possible lung malignancy). She denies use of antacids, there has been no weight loss (malignancy less likely), and the patient has not been immobilized. Importantly, there is no family history of hypercalcemia or endocrinopathy. With the elevated PTH, the most likely cause is primary hyperparathyroidism. It is unlikely she has familial hypocalciuric hypercalcemia (FHH), because FHH is autosomal dominant and a family history of hypercalcemia is usually apparent, the hypercalcemia is mild, and the PTH is only mildly elevated. FHH is caused by mutations in the Ca-sensing receptor. In FHH the urine calcium excretion is low, and in primary HPT is high, a 24 hour urine calcium measurement will help sort out the issue; therefore, the correct answer is A
The causes of renal failure in the setting of hypercalcemia are listed below:
The differential diagnosis for the hypercalcemia are below:
–A.) A urine pH of 5.0
–B.) The presence of hyperkalemia
–C.) A negative urine anion gap of -22
–D.) A serum bicarbonate of 18
–E.) A normal anion gap
____________Answer to Sep 16 Electrolyte Quiz is A. Perform a 24 hour urine collection for calcium (case provided by Dr. Alan Yu)
A 59 year old white female presents with a 1 week history of constipation, nausea, polyuria, and polydipsia. She says that she has been consuming cod liver oil after seeing it recommended on a recent health program on television. The patient also reported chronic cough productive of mucoid sputum, unchanged for the preceding 6 years except for one recent episode of slight hemoptysis. She denies use of antacids, weight loss, has not been immobilized, and there is no family history of hypercalcemia or endocrinopathy. Her baseline renal function was normal. Medications: hydrochlorthiazide 50 mg/day for essential hypertension. Examination was unremarkable except for dry mucous membranes. Vital signs: blood pressure 122/78 mmHg, heart rate 92 beats/minute, respiratory rate 14 breaths/minute. Laboratory data shows: Sodium 131 mEq/L, potassium 3.1 mEq/L, Chloride 95 mEq/L, CO2 32 mEq/L, Glucose 108 mg/dL, BUN 29 mg/dL, Cr 1.9 mg/dL, Alb 3.8g/dL, Calcium 17.2 mg/dL and PO4 2.3 mg/dL. Her iPTH is 291 pg/ml (10-65), 25-vitamin D 23 pg/ml (9-43), 1,25-vitamin D 30 pg/ml (15-60), TSH is normal. Her SPEP/UPEP show no monoclonal bands. A skeletal survey is negative and a chest X-ray and chest CT scan are both negative.
The next step in her management should be:
- Perform a 24 hour urine collection for calcium
- Check a PTHrP
- Check a bone scan
- Check a serum aluminum (aluminium) level
- Check a vitamin A level
Explanation:
There are important clues from the history: the history already reveals use of cod liver oil (vitamin A and D), thiazides, and respiratory symptoms (possible lung malignancy). She denies use of antacids, there has been no weight loss (malignancy less likely), and the patient has not been immobilized. Importantly, there is no family history of hypercalcemia or endocrinopathy. With the elevated PTH, the most likely cause is primary hyperparathyroidism. It is unlikely she has familial hypocalciuric hypercalcemia (FHH), because FHH is autosomal dominant and a family history of hypercalcemia is usually apparent, the hypercalcemia is mild, and the PTH is only mildly elevated. FHH is caused by mutations in the Ca-sensing receptor. In FHH the urine calcium excretion is low, and in primary HPT is high, a 24 hour urine calcium measurement will help sort out the issue; therefore, the correct answer is A
The causes of renal failure in the setting of hypercalcemia are listed below:
- Vasoconstriction
- Dehydration
- Acute interstitial nephritis
- Intratubular obstruction
- Chronic interstitial nephritis
- Renal calculi
The differential diagnosis for the hypercalcemia are below:
- Milk-alkali syndrome
- Lytic bone metastases, hematologic malignancy, immobilized Paget’s, hyperthyroidism, hypervitaminosis A, aluminum osteomalacia
- Thiazides
- 1° & 3° hyperparathyroidism, Li, FHH
- Malignancy
- Hypervitaminosis D, sarcoidosis
