Journal of Medicine Vol 4 - Amrita Institute of Medical Sciences and ...

Amrita Journal of Medicine
proximal motor neuropathy and metabolic bone disease.
Going a step further, the temporal profile of the illness,
absence of fluctuating weakness/ wasting/
fasciculations/ normal reflexes, narrow down the possibility
to a muscle disease. Prior records from various
hospitals showed that electrodiagnostic studies, serum
CPK and muscle biopsy were all normal. She had also
received steroids, but showed no response, thereby
favouring the possibility of a metabolic myopathy rather
than an inflammatory one.
FUEL FOR THOUGHT
She was investigated at various hospitals and found
to have a raised alkaline phosphatase, normal calcium
and low phosphorus, which was considered as secondary
to hypovitaminosis D and hence she was put on Vit D
and Calcium supplements without any improvement (she
rather worsened).
WHY NO RESPONSE AFTER 4 YEARS OF
APPROPRIATE TREATMENT WITH
VITAMIN D AND CALCIUM???
Fig.1: Multiple fractures of ribs and pelvis
Fig. 1a
Nasal Cure for a Myopathy- A Neuroendocrine Puzzle?
SEEKING ANSWERS FROM LABORATORY
AID’S:
Metabolic workup (Table 1) revealed hypophosphatemia
with normal calcium & a high alkaline
phosphatase. However, Serum Vit D3 and PTH levels
were mildly elevated. Her tubular maximum for phosphate
(TmP/GFR) corrected for GFR (index of renal
threshold for phosphate, which is independent of plasma
Fig. 1b
phosphate) was reduced. X-rays revealed multiple fractures
at the site of maximum pain (Fig.1a & 1b). Whole
body skeletal scintigraphy was performed which was suggestive
of a metabolic bone disease rather than an
infiltrative disorder.
Table 2: Biochemical findings in the major acquired conditions characterized by hypophosphataemia and musculoskeletal
symptoms 2
Condition Plasma indices Urinary indices
Nutritional osteomalacia Calcium or low/normal Calcium
25 OH Vit D Phosphate normalc
1,25 Di OH Vit D , normal or a
PTH
ALP b
Oncogenic osteomalacia Calcium normal Calcium normal
25 OH Vit D normal Phosphate normalc
1,25 Di OH Vit D or normal
PTH normal or
ALP b
Primary hyperparathyroidism Calcium Calcium normal d or
25 OH Vit D normal Phosphate normalc
1,25 Di OH Vit D normal or
PTH
Humoral hypercalcaemia of Calcium Calcium
malignancy (PTHrPe)
25 OH Vit D normal
1,25 Di OH Vit D normal or
PTH normal or
ALP normal
a. Depends on any recent exposure to vitamin D. b. Occasionally within normal limits. c. But renal phosphate
clearance always high. d. Owing to increased renal tubular reabsorption. e. Effects mediated by PTH-related
peptide. Differences between the condition and primary hyperparathyroidism broadly reflect the effects of relative end
organ resistance to PTHrP compared with PTH.
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