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Case Study 2
CASE STUDY 2
A 45-year old high school teacher
with seizures and asthma
Submitted by Marjorie M. Luckey, MD
PATIENT PROFILE
Susan T. is a 45-year-old African American
high school teacher. Her history includes
surgical menopause five years previously.
She never took estrogen and currently has
mild vasomotor symptoms only. She was
diagnosed with a seizure disorder at age
20 and is currently well controlled on
phenytoin 300 mg daily. She has had asthma
since childhood; her current medications
include a b.i.d. steroid inhaler and oral
glucocorticoids 5-6 times per year for 2-6
weeks for exacerbations. She takes a multivitamin
daily, TumsŪ 500 mg b.i.d., and
has one dairy serving daily. She has no
history of osteoporotic fractures.
Her physical exam results showed a height
of 5'5" (no loss), a weight of 150 lbs, and
a BP of 140/82. Expiratory wheezes were
noted. Her lab test results showed the following:
sCa: 8.9 (normal: 8.6-10.2), normal
CBC, normal cholesterol, 24-hour
urine calcium: 50 mg, and 25 OH vitamin
D: 8 ng/mL (normal: > 20). Her BMD
results are listed in the table below.
DISCUSSION
This patient's BMD is much lower than
would be expected for her age, which suggests
a secondary cause for her bone loss.
Although African American women are
less prone to develop osteoporosis than
Caucasian women, this case underscores
the importance of obtaining BMD scores
in all ethnic groups. All women should be
screened by age 65, while those with risk
factors, such as exposure to drugs that may
cause bone loss, should be screened earlier.
Compared with normal mean BMDs for
African American women, Susan's T-score
suggests that she is at significant risk for
fractures, while her Z-score suggests a secondary
cause of bone loss. In fact, she has
several risk factors for secondary osteoporosis,
including early surgical menopause
and chronic exposure to anticonvulsants and
corticosteroids. In this case, the primary
culprit was a vitamin D deficiency: vitamin D
is critical for calcium absorption. In addition
to reducing calcium absorption, vitamin D
deficiency has adverse neuromuscular effects
that significantly increase the risk of falls
and fractures. It has recently been recognized
that 15-20% of the Caucasian
population has vitamin D deficiency,
and the incidence is even higher in the
African American population. One cause
of vitamin D deficiency is anticonvulsant
therapy; many anticonvulsants, including
phenytoin, interfere with the metabolism
of vitamin D. In general, people under age
70 should receive 400 units of vitamin
D daily; for those 70 and older, the recommended
dose is 600-800 units, while
patients with osteoporosis should have a
daily vitamin D intake of 800-1000 units.
In summary, this case is a timely reminder
that not all low bone density is simple
osteoporosis. Several potential causes of
secondary osteoporosis needed to be
addressed before she could be treated
successfully for bone loss.
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