A 57 year old man presented to his physician for an annual physical examination.
ID: 126039 • Letter: A
Question
A 57 year old man presented to his physician for an annual physical examination. He had no specific complaints and claimed to be in good health. No abnormal findings were presented on physical examination. Laboratory findings were unremarkable except for an elevated total alkaline phosphate (ALP) of 249 U/L (reference range, 25-90 U/L). There was no indication of liver disease by palpitation, malignancy by increased globulins, or bone dyscrasia. The patient did not recall any incident that may have induced any medication other than aspirin (approximately four tablets per month). Laboratory results are shown. Repeated laboratory tests yielded similar findings.
1. What condition(s) could be responsible for the ALP elevation?
2. What tests could be ordered for the differential diagnosis of elevations in ALP?
3. What other biochemical tests are used for the diagnosis of bone disorders?
Explanation / Answer
1. What condition(s) could be responsible for the ALP elevation?
Answer: As ALP are a group of zinc metalloenzymes that catalyze the hydrolysis of phosphate esters with widespread tissue distribution. This enzyme works best at an alkaline pH, and thus the enzyme is virtually inactive in the blood. Alkaline phosphatases act by splitting off phosphorous, creating an alkaline environment. They are found predominantly in the liver and bone, with intestinal enzymes contributing up to 20% of total activity; other tissue beds include the kidney, placenta, adrenal cortex, lung. Possible reasons for elevated ALP in the given condition could be any of the following disease;
-Primary malignancy (lymphoma, hepatocellular carcinoma) - -Sarcoidosis, tuberculosis, and other granulomatous diseases
- Fatty liver
Amyloidosis
2. What tests could be ordered for the differential diagnosis of elevations in ALP?
Answer: The differential diagnosis required for this patient could be to rule out the followings by detailed history collection and diagnostic evaluation
- History of any fractures and osteoporosis
- Nutritional status -dietary pattern, patterns of bowel movements
- Complete Blood analysis – including Vitamin B12 and Vitamin D, haematocrit values.
- Renal function tests
- Cardiac function tests – ECG, Echogram
- Radiological study – to rule out the fractures and osteoporosis
- Bone densitometry
- USG studies to rule out genito-urinary functions.
- Thyroid function tests
The above tests may help us to rule out other differential diagnosis in our patient scenario
- Gastrointestinal inflammation (ulcerations, inflammatory bowel disease)
- Cancer (bronchogenic, breast, colon, ovarian, cervical, prostate)
- Hyperphosphatemia
- Pernicious anemia
- Myocardial, renal, and sometimes pulmonary infarction
- Renal failure (renal osteodystrophy, decreased clearance
C. Bone diseases;
- Paget's disease (historically known as osteitis deformans)
- Physiologic and pathologic bone growth (healing fracture, osteoblastic bone tumors, metastatic cancer to the bone, myeloma, osteomalacia)
- Hyperthyroidism
- Hyperparathyrodism (osteitis fibrosa cystica)
- Chronic osteomyelitis
- Vitamin D deficiency
- Treatment of osteoporosis
- Acromegaly
3. What other biochemical tests are used for the diagnosis of bone disorders?
Answer: the possible bone diseases could be tested by following tests
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