Here is another case:
A 62-year old woman is evaluated for
worsening right leg pain over two years.
The pain is worse with weight bearing.
She is post-menopausal and
is in otherwise good health.
There is no family history of fractures.
She takes no medications.
And on physical exam, the vital signs are normal.
Her BMI is 36.
She is pale and has difficulty bearing
weight and limps when walking.
She has discomfort on palpation
over the right anterior tibia.
The remainder of the physical exam is normal.
Her labs show a calcium of 8.2 mg/dL, a
phosphorous of 2.4 mg/dL, a PTH of 179 pg/mL,
alkaline phosphatase of 145 U/L and 25-hydroxy
vitamin D level that is less than 6 ng/mL
What is the most likely diagnosis?
This patient is post-menopausal,
she has skin pallor and bone pain.
She has difficulty walking and her
labs show a very low vitamin D level,
low calcium and phosphorous as well as
elevated PTH and elevated alkaline phosphatase.
This patient has severe prolonged vitamin D
deficiency and likely associated osteomalacia
The presence of pallor on this patient's
physical exam is a good clue that you may have
prolonged lack of exposure to sunlight and consequently
is manifesting with asymptomatic expression
of very very low vitamin D levels.
Osteomalacia is most commonly caused by
severe prolonged vitamin D deficiency
which leads to inadequate concentrations
of calcium and of phosphate in the bone.
It prevents the mineralization
of newly-formed bone as well.
Chronically low levels of vitamin D can lead to
rickets in children and osteomalacia in adults.
Vitamin D deficiency is caused by factors
such as intestinal malabsorption
due to gastrointestinal disorders
or restricted access to sunlight.
In promoting absorption from the gut, vitamin
D enables proper bone mineralization
by maintenance of calcium
and phosphorous levels.
Vitamin D also modulates the action of osteoblasts and
osteoclasts, ensure proper bone growth and remodelling.
Usually low 25-hydroxy vitamin D, low calcium and phosphate and
elevated parathyroid hormone secondary to hypoparathyroidism
as well as an elevation of alkaline phosphatase
are seen as we found classically in our patient.
A 1,25 dihydroxyvitamin D
may be normal, low or high
and is not usually helpful in the
diagnosis of most forms of osteomalacia.