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$Unique_ID{BRK04189}
$Pretitle{}
$Title{Rickets, Hypophosphatemic}
$Subject{Rickets, Hypophosphatemic Familial Hypophosphatemic (Vitamin
D-Resistant) Rickets X-Linked Hypophosphatemia X-Linked Vitamin D-Resistant
Rickets Hypophosphatemic D-Resistant Rickets I HPDR I Hereditary Type II
Hypophosphatemia Hypophosphatemic D-Resistant Rickets II HPDR II Phosphate
Diabetes Rickets Pseudovitamin D Deficiency Rickets (Vitamin D-Dependent
Rickets, Type I) Osteomalacia Fanconi's Syndrome }
$Volume{}
$Log{}
Copyright (C) 1987, 1988, 1989, 1992 National Organization for Rare
Disorders, Inc.
417:
Rickets, Hypophosphatemic
** IMPORTANT **
It is possible the main title of the article (Hypophosphatemic Rickets)
is not the name you expected. Please check the SYNONYMS listing on the next
page to find alternate names, disorder subdivisions, and related disorders
covered by this article.
Synonyms
Familial Hypophosphatemic (Vitamin D-Resistant) Rickets
X-Linked Hypophosphatemia
X-Linked Vitamin D-Resistant Rickets
Hypophosphatemic D-Resistant Rickets I
HPDR I
Hereditary Type II Hypophosphatemia
Hypophosphatemic D-Resistant Rickets II
HPDR II
Phosphate Diabetes
Information on the following diseases can be found in the Related
Disorders section of this report:
Rickets
Pseudovitamin D Deficiency Rickets (Vitamin D-Dependent Rickets, Type I)
Osteomalacia
Fanconi's Syndrome
General Discussion
** REMINDER **
The information contained in the Rare Disease Database is provided for
educational purposes only. It should not be used for diagnostic or treatment
purposes. If you wish to obtain more information about this disorder, please
contact your personal physician and/or the agencies listed in the "Resources"
section of this report.
Hypophosphatemic Rickets is a rare genetic form of Rickets characterized
by impaired transport of phosphate and diminished Vitamin-D metabolism in the
kidneys. Additionally, calcium and phosphate are not absorbed properly in
the intestines which can lead to softening of bones. Major symptoms include
skeletal changes, weakness and slowed growth. Cases affecting females are
usually less severe than those affecting males. One rare acquired form of
this disorder may be associated with a benign tumor.
Symptoms
Symptoms of Hypophosphatemic Rickets are usually first noticed after eighteen
months of age. Dental problems may develop such as decay and abscesses or
late eruption of teeth. Abnormalities may include softening or thinning of
bones, fractures, and/or abnormal bony extensions at the site of muscular
attachments. Symptoms such as weakness, intermittent muscle cramps, a
"waddling" walk due to abnormalities in the hip joint, pain in the knees,
knock knees or bow legs, diminished growth (especially of the legs), and
abnormal skull or rib development may also occur. Cases of Hypophosphatemic
Rickets may range from mild to severe. Some cases may have no noticeable
symptoms while others may be marked by pain and/or stiffness of the back,
hips and shoulders possibly limiting mobility. In very rare cases, some hair
loss may occur.
Causes
Hypophosphatemic Rickets is inherited as a dominant X-linked trait. Symptoms
are caused by altered metabolism of phosphorus, calcium, and Vitamin-D
although the exact mechanism through which this occurs is not well
understood.
Human traits including the classic genetic diseases, are the product of
the interaction of two genes for that condition, one received from the father
and one from the mother. In X-linked dominant disorders the female with only
one X chromosome affected will develop the disease. However the affected
male always has a more severe condition. Sometimes affected males die before
birth so that only female patients survive.)
Affected Population
Hypophosphatemic Rickets may affect males and females in equal numbers,
although cases affecting males are usually more severe than those affecting
females.
Related Disorders
Several forms of Rickets exist, all of which are characterized primarily by
weakening of bones due to abnormal calcium metabolism as well as possible
decreases of other substances in the body. Rickets may be either acquired or
inherited. Asymptomatic hypophosphatemic adult carriers are almost always
females.
Symptoms of the following disorders can be similar to Hypophosphatemic
Rickets. Comparisons may be useful for a differential diagnosis:
Rickets is due to a vitamin-D deficiency resulting in deficient
calcification of tissue which normally hardens into bone. This condition can
begin at any time of life and may be successfully treated with large doses of
vitamin-D.
Pseudovitamin D Deficiency Rickets (Vitamin D-Dependent Rickets, Type I)
is characterized by more severe skeletal changes and weakness than those of
Hypophosphatemic Rickets. This disorder is caused by abnormal vitamin D
metabolism and is inherited as an autosomal recessive trait. This type of
rickets often begins earlier than Hypophosphatemic Rickets. Blood levels of
calcium are severely diminished in patients Vitamin-D Dependent Rickets,
although phosphate levels appear normal or only slightly deficient. Amino
acids become lost in the urine due to a kidney dysfunction. Intermittent
muscle cramps may occur. Convulsions and abnormalities of the spine and
pelvis may also develop.
Osteomalacia is a disorder characterized by a gradual softening and
bending of the bones. Pain may occur in various degrees of severity.
Softening occurs because solid bones have failed to form properly (calcify)
due to lack of Vitamin-D or a kidney dysfunction. This illness is more
common in women than in men, and often begins during pregnancy. It can exist
alone or in association with other disorders, such as Hypophosphatemic
Rickets.
Fanconi's Syndrome is characterized by kidney dysfunction and bone
abnormalities similar to those of Hypophosphatemic Rickets. Excess amounts
of phosphate, amino acids (usually bicarbonate), glucose, and uric acid are
eliminated in the urine. This rare disorder is thought to be inherited
through a recessive gene. Bone symptoms include rickets in children and
softening of bones (osteomalacia) in adults. Fanconi's Syndrome may be
associated with a variety of inherited metabolic disorders such as
cystinosis, Lowe's Syndrome, a form of Tyrosinemia, hereditary fructose
intolerance, Wilson's Disease, Galactosemia, and a glycogen storage disorder.
For more information on the above disorders, choose the following words
as your search terms in the Rare Disease Database: Fanconi, Lowe, fructose
intolerance, cystinosis, Wilson, galactosemia, and glycogen storage.
Therapies: Standard
Treatment of Hypophosphatemic Rickets consists of increasing phosphate levels
as well as vitamin-D. The dosage of vitamin-D is gradually increased until
bone healing occurs. This treatment must be carefully monitored to prevent
loss of calcium. Vitamin-D alone decreases loss of phosphate through the
kidney but does not influence the patient's growth pattern, the level of
phosphate absorbed in the intestines, nor the kidney dysfunction. Phosphate
alone may improve absorption of calcium and phosphate in the intestines as
well as enhance bone healing, but it may not sustain these improvements
unless vitamin-D is also prescribed. Recent evidence suggests that long-term
calcium plus phosphate supplements may result in better bone mineralization
than occurs with vitamin-D plus phosphate therapy. Covering teeth with
chrome crowns may be successful in preventing spontaneous abscesses. Genetic
counseling may be of benefit for patients and their families. Those rare
cases which are caused by tumors rather than heredity can be treated through
surgical removal of the tumor.
Therapies: Investigational
Bone growth abnormalities associated with Hypophosphatemic Rickets can be
surgically removed in an attempt to prevent further shortening or deformities
of affected arms or legs. More research is necessary before this procedure
can be recommended for all but the most severe cases of Hypophosphatemic
Rickets.
In a study carried out by scientists in Australian children with X-Linked
Hypophsatemic Rickets using the enzyme calcitriol (1x, 25 dihydroxyvitamin
D3) and phosphate, a slight increase in height was noted along with the
development of calcium deposits in the kidneys (nephrocalcinosis). These
scientists recommend conservative use of calcitriol nd careful observation of
patients to guard against serious kidney damage. Treatment should be
discontinued when growth has stopped.
This disease entry is based upon medical information available through
February 1992. Since NORD's resources are limited, it is not possible to
keep every entry in the Rare Disease Database completely current and
accurate. Please check with the agencies listed in the Resources section for
the most current information about this disorder.
Resources
For more information on Hypophosphatemic Rickets, please contact:
National Organization for Rare Disorders (NORD)
P.O. Box 8923
New Fairfield, CT 06812-1783
(203) 746-6518
National Digestive Diseases Information Clearinghouse
Box NDDIC
Bethesda, MD 20892
(301) 468-6344
For information on genetics and genetic counseling referrals, please
contact:
March of Dimes Birth Defects Foundation
1275 Mamaroneck Avenue
White Plains, NY 10605
(914) 428-7100
Alliance of Genetic Support Groups
35 Wisconsin Circle, Suite 440
Chevy Chase, MD 20815
(800) 336-GENE
(301) 652-5553
References
PROPHYLACTIC DENTAL TREATMENT FOR A PATIENT WITH VITAMIN D-RESISTANT RICKETS:
REPORT OF CASE: G. H. Breen; Asdc J Dent Child (Jan.-Feb. 1986, issue
53(1)). Pp. 38-43.
EARLY DIAGNOSIS AND EARLY TREATMENT OF HYPOPHOSPHATEMIC VITAMIN D-
RESISTANT RICKETS: E. Schaumberger, et al.; Klin Padiatr (Jan.-Feb. 1986,
issue 198(1)). Pp. 44-48.
TIBIAL BOWING EXACERBATED BY PARTIAL PREMATURE EPIPHYSEAL CLOSURE IN SEX-
LINKED HYPOPHOSPHATEMIC RICKETS: W.H. McAlister, et al.; Radiology (February
1987, issue 162(2)). Pp. 461-463.