You come across the following set of serum results from a 72 year old lady,
seeing her Community Physician. Clinical details on the request form are
'crest syndrome'.
Sodium: 140 mmol/L
Potassium: 3.5 mmol/L (3.6 - 5.3)
Urea: 17.1 mmol/L (2.8 - 7.0)
Creatinine: 122 umol/L (62 - 133)
Albumin: 29 g/L (35 - 49)
Total calcium: 1.63 mmol/L
Corrected calcium: 1.91 mmol/L (2.10 - 2.55)
Magnesium: 0.12 mmol/L (0.70 - 0.91)
This extreme case attracted 28 participants, and no major disagreements
between the assessors).
3 would find out what CREST syndrome was before commenting; [1.3]
12 would phone the CP to alert him to the low magnesium and/or to check the
clinical history; [2.0]
6 advised that iv magnesium supplementation was probably needed. [0.8]
14 suggested that the low calcium (and potassium) may be secondary to the
low magnesium; [1.5]
11 queried dysphagia/ malabsorption/ GI tract loss; [1.3]
8 mentioned drug (diuretic) effects; [0.3]
7 thought the high urea was caused by a pre-renal problem/ reduced fluid
intake; dehydration; [0.5]
3 queried renal involvement; [-0.3]
1 said renal involvement is uncommon in CREST [-0.3]
3 advised repeating the sample ensuring no EDTA contamination; [-0.3]
4 would ask for a repeat sample to check the magnesium. [1.3]
4 would check urine magnesium; [0.5]
2 would check albumin/ globulins; [-0.3]
2 would measure anticentromere antibody to confirm CREST; [0]
1 would measure anti Scl 70 to assess a possible alternative diagnosis of
progressive systemic sclerosis. [-0.3]
1 each would measure
LFTs [0]
creatinine clearance; [0]
phosphate; [0.3]
PTH; [0.5]
urine microalbumin; [-0.8]
Vitamin D. [0]
3 would ask for a repeat sample after correction of low magnesium; [1.3]
1 would measure PTH on this repeat sample if the calcium remained low.
[0.8]
I was concerned about the very low magnesium in this patient, and 'phoned
the physician about it, telling him rather shamefacedly that I did not know
what crest syndrome was. The physician didn't know either - the diagnosis
had been made some years before. On previous investigations, the patient
usually had a low magnesium - once as low as 0.35 mmol/L. She had been
given oral magnesium supplements then, but had not tolerated this well. She
was restarted on oral magnesium supplements, and the magnesium climbed as
high as 0.79 mmol/L; but I note today it has slipped back to 0.45 mmol/L.
Two participants (thank you, Gerald and Roy) were kind enough to tell us
what crest syndrome is: an American acronym for
Calcinosis
Raynaud's
Esophogeal dysmotility
Sclerodactyl
Telangectasia
also apparently known as limited cutaneous scleroderma.
My original comment on the report was (please note the maximum limit of two
lines!)
Telephoned. Looks dehydrated. Low divalent cations particularly magnesium.
Replacement needed?
Best wishes
Gordon Challand
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