by Wayne Fuchs, MD
(from
Volume 4, Issue 2, Spring 1996)
There is strong scientific evidence that nutrition plays a
role in a variety of diseases. Patients with PXE develop
calcification of elastic tissue in the skin, blood vessels
and the eyes and are concerned about the amount of calcium
in their diet. This article will examine the role of a
reduced calcium diet in preventing the complications of this
disorder.
One study of 32 patients was performed in 1984 by Renie1,
who found a relationship between overall severity of
PXE and calcium intake during adolescence. Increased
calcification, which was assumed to correspond to the
severity of clinical disease, was also noted to increase
with age. The author concluded that the pathology was
independent of the pattern of inheritance. Some limitations
of the study discussed by the author include the small
number of subjects, and the questionable validity of the
manner in which the data was collected.
A study published in 1979 by Reeve2 also showed
that a positive relationship existed between
childhood-adolescent calcium intake and severity of
disease. In this series of 39 patients followed over one
year, little or no progression was noted of any aspect of
the disease in those adhering to a low-calcium diet.
Limitations of this study acknowledged by the author
included a brief follow-up period in a slowly progressive
disorder, and questionable patient compliance. An important
point discussed was their observation of reversibility of a
skin lesion in a 12-year-old girl with PXE on an 800 mg/day
calcium diet. Reversibility was previously documented by
Eng3 in 1975.
These studies, although limited by their small numbers of
subjects and methods of data collection, offer us some
useful guidelines. Although far from scientifically proven,
which would require a large-well-designed trial, it appears
that the intake of calcium in adolescent years should be
reduced in patients with PXE. It should be noted that 90%
of dietary calcium is derived from dairy products, and that
a reduction in the consumption of these may offer secondary
benefits in a disease which can be associated with
accelerated atherosclerosis. The benefits of a reduction of
calcium in the diet must be weighed against the potential
risks in both men and women. It is especially important for
females, who must consider the risks of a low-calcium diet
on the aggravation of osteoporosis, especially in their post
menopausal years.
Osteoporosis is defined as a disorder of skeletal strength
predisposing to fracture, and is one of the most common
conditions with advancing age. In recent years, scientific
evidence has supported a beneficial effect of dietary
calcium supplements on maintenance of bone mass in post
menopausal women. The controversy is whether a young adult
should increase his/her dietary calcium in an effort to
achieve full genetic potential for adult bone mass. To
achieve this, recommendations include regular and vigorous
exercise, and avoidance of excesses in protein, sodium
(salt), alcohol and smoking, as well as high maintenance of
calcium intake.
Some experts have based recommendations upon the studies and
considerations previously discussed. A reduced calcium diet
is reasonable at the adolescent age in patients with PXE.
However, every effort must be made to achieve peak bone mass
through other factors. At least a threshold level of
calcium intake during adolescence is needed for
approximately 800 mg/day from dairy foods for reasonably
good bone development prior to age 18. It is estimated that
girls entering puberty in the U.S. consume on the average
only 55-60% of the calcium Recommended Dietary Allowance
(RDA) of 1200 mg/day for ages 12-24. The calcium intake of
boys tends to be closer to the RDA. Moderate to heavy
physical exercise during the adolescent years contributes to
the enhanced bone mass as do normal menstrual cycles.
Patients with PXE should avoid exercise which places them at
risk for direct eye trauma, which could cause a retinal
hemorrhage and subsequent vision loss. One should reduce
the phosphorus in the diet as a low calcium to phosphorus
ratio contributes to bone loss. Phosphorus is contained in
all food groups especially animal proteins and soda.
A problem is that the diagnosis of PXE is often not
established at such a young age, as the disease may be
subtle and is frequently overlooked. This emphasizes the
importance of examining family members of affected
individuals at an early age for evidence of disease, when
manipulation of the diet may be most beneficial.
It is a widely held view that the RDA for calcium should be
1500 mg/day for post menopausal women to prevent bone loss.
The importance of adequate vitamin D status is critically
important, especially in the older population, and may be
enhanced by consuming fortified foods or vitamin
supplements. Certainly by this age, the severity of PXE in
a particular patient would be established and serve as a
guide. In a patient with no ocular findings and no history
of bleeding, one would be more likely to follow the RDA. A
patient who has experienced complications from PXE would be
willing to accept the increased fracture risk and continue
on a low calcium diet.
1
Renie, W.A. Pyeritz, R.E., Combs, J., & Fine, S.,
Pseudoxanthoma elasticum: High calcium intake in early life
correlates with severity. American Journal of Medical
Genetics, 1984, 19, 235-244.
2
Reeve, E.B., Neldner, K.H., Subryan, V., & Gordon, G.S.,
Development and calcification of skin lesions in thirty-nine
patients with pseudoxanthoma elasticum. Clinical
Experimental Dermatology, 1979, 4, 291-244.
3
Eng, A., & Bryant, J., Clinical pathologic observations in
pseudoxanthoma elasticum. International Journal of
Dermatology, 1975, 14, 586-605.
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