HOSP #		WARD	Victoria Hospital Female medical ward
CONSULTANT	Heleen Vreede	DOB/AGE	29y female

Abnormal Result

The magnesium result measured 0.36 mmol/L ( 0.63 – 1.05 mmol/L) despite adequate levels prior to admission to hospital (0.75 mmol/L on 18/04/2020).

Presenting Complaint

The patient was asymptomatic with regards to the at the time when the result was obtained.

History

Patient was diagnosed with Cryptococcal Meningitis on 22/04/2020 with a cryptococcal latex agglutination test.

Patient was known HIV positive with a CD4-count of 9 cells/uL (332-1642).

Examination

Unfortunately this data is not available.

The clinical features of hypomagnesemia is predominantly related to the derangement in the calcium becoming deranged when hypomagnesemia occurs.

Laboratory Investigations

Other Investigations

None available.

Final Diagnosis

Hypomagnesemia with accompanying hypocalcemia due to Amphoterecin B therapy

Take Home Message

• I’ve learned from the attending clinician (and a short literature search) that Hypomagnesemia is a known consequence of Amphotericin B therapy.
• Hypocalcemia is often a consequence of hypomagnesemia (as in this case). This is due to two known mechanisms:
  • Decreased sensitivity of Calcium at the calcium-sensing receptor, with decreased secretion of PTH and hence its effects.
  • Decreased action of PTH due to PTH-receptor resistance being caused by hypomagnesemia.

HOSP #		WARD	Internal Medicine ward
CONSULTANT	George vd Watt / Heleen Vreede / David Marais	DOB/AGE	58 y Male

Abnormal Result

Upon signing out blood results:

Calcium = 1.41 mmol/L – Critically low Calcium result

Magnesium = 0.37 mmol/L – Critically low Magnesium

Presenting Complaint

Loss of breath initially accompanied by weight loss.

Upon admission to the ward, patient was slightly delirious, but still able to walk and talk.

History

Patient with metastatic lung cancer and accompanying hypercalcemia, a week prior to the results as at present.

Doctor has given IV Bisphosphonate after the hypercalcemia was noted a week prior (Calcium = 4.23 mmol/L; Alb = 21 g/L; Corrected Ca = 4.61 mmol/L)

Examination

Extensive Crepitations over all the right lung fields.

Laboratory Investigations

Other Investigations

Final Diagnosis

Invasive lung CA with “hungry bones” after IV Zolendronic Acid

Vitamin D deficiency, preventing Calcium absorbtion after the Zolendronic acid started its action of inhibiting bone resorption.

Take Home Messages

CA causes hypercalcemia

Bisphosphonates inhibits bone resorption. Because 99.95% of Ca in the body resides in bone, the effect in serum (the remaining 0.05% of total body Ca) can be significant.

All bisphosphonate drugs share a common phosphorus-carbon-phosphorus “backbone”:

They differ in the R-groups as above. It binds to calcium hydroxyapatite in bone.

Of the dose infused / absorbed, 50% is excreted unchanged by the kidney, the rest binds to bone tissue, where its elimination half life can apparently be up to 10 years! (UW Courses Web Server- https://courses.washington.edu/bonephys/opbis.html )

Because a bisphosphonate group mimics the structure of pyrophosphate, it can inhibit activation of enzymes that utilize pyrophosphate.

Magnesium follows Calcium levels, but Mg deficiency itself can also cause hypocalcemia.