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6.3 Growth Hormone Diseases 213
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Signs on Brain MRI
Pituitary adenoma is seen as a bulging lesion in the superior
or inferior aspect of the pituitary gland with low T1/high T2
signal. The adenoma is hypointense compared to the normal
pituitary tissue on postcontrast images (Fig. 6.3.6 ).
a
Fig. 6.3.5. Anteroposterior plain radiograph of the third and
fourth fi ngers of a patient with acromegaly shows widening of
the distal phalangeal tufts (spade-like appearance)
Increased soft tissue thickening of the heel pad (normal up to
23 mm in men and 21 mm in women).
Hypertrophic osteoarthritis of the joints.
Locking of the metacarpals is a relatively rare condition that
can be seen in patients with acromegaly. The condition is
characterized by a hook-like osteophytes formation in the
heads of the metacarpal bones. As the patient makes a fi st or
grasps something, the volar distal part of the proximal
phalanx will be locked against the osteophyte in the
metacarpal head, locking the fi nger in the grasping position.
Hyperostosis frontalis interna is a condition where thickening
of the inner surface of the frontal bone may be seen in some
cases with acromegaly.
In van Buchem disease, there is generalized skull hyperostosis,
mandibular hyperostosis and enlargement, ribs and clavicular
thickening, and diaphyseal endosteal sclerosis that spares the
bone ends, especially in the phalanges. Unlike acromegaly,
there is no dental widening or mandibular prognathism.
b
Fig. 6.3.6. Sagittal T1W ( a ) and T1Wpostcontrast ( b ) sella MRI
in a patient presented with features of acromegaly. The MR
examination showed macroadenoma with cystic changes. The
adenoma is detected as a mass with low contrast enhancement
( arrowhead ) compared with the highly enhanced normal pitu-
itary tissue due to its rich blood supply
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6.3
Indirect signs of pituitary adenoma include: convex upper border
of the gland with shifted pituitary stalk. When the cavernous
internal carotid artery is completely surrounded by the tumor,
then the cavernous sinus is mostly invaded by the tumor.
Growth Hormone Insensitivity (Laron
Syndrome)
Laron syndrome (LS) is a rare, autosomal recessive,
congenital disease characterized by GH receptors gene
defects, resulting in lack of body tissue response to GH.
Patients with LS present with dwarfi sm, severe
growth retardation, and characteristic facial features.
Most cases are reported from patients with Oriental
Jewish origin, or patients originating in the Mediterranean
area like Arab, Turkish, Iranian, and Pakistani origin.
Patients with LS typically have small chin (micrognathia), underdeveloped facial bones, smaller head circumference according to age, protruding forehead, and
saddle nose deformity due to nasal bone underdevelopment. The teeth are defective and crowded due to micrognathia. The hair is silky and shows frontal and temporal
thinning. Alopecia is often seen in males (Fig. 6.3.7 ).
Patients are usually obese due to underdevelopment
of bones and muscles. The children and even adults
have very high-pitched voices due to narrow oropharynx. Hands and feet are small (acromicria). The genitalia and gonads are small since birth, and males show
delayed puberty more than females. LS patients do not
have real pubertal growth spur.
Laboratory investigations show severe hypoglycemia in neonates that improves with age, low serum
alkaline phosphatase and creatinine, low serum cholesterol, and low density lipoproteins.
Hormonal investigations show increased serum GH
levels with very low serum levels of insulin-like growth
factor-I (IGF-I). IGF-I is the anabolic effector hormone
of GH. Prolactin levels may be elevated due to a drift
phenomenon to the GH secretion. Serum insulin level
is usually high with hypoglycemia.
Signs on Radiographs
Generalized bone maturation delay and osteoporosis.
Epiphyseal closure occurs after age 16–18 in girls and 20–22
in boys.
Underdeveloped facial bones, with thin diploe of the skull.
Atlanto-axial joint degeneration and spinal stenosis is often
observed.
Os odontoideum may be seen. Os odontoideum is a situation
where the axial den (odontoid process) is hypoplastic, absent
or separated from the axis body as a congenital variant (not
due to previous trauma). It is due to failure of the three dens
ossifi cation centers to fuse together with the axis body. It is
seen as a round ossicle with smooth edges over the axis body
in open mouth view (best view to evaluate the dens). It is may
be impossible to diff erentiate os odontoideum from a previous
old dens fracture without history.
Fig. 6.3.7. An illustration of a child demonstrates the characteristic features of Laron syndrome (LS) like micrognathia, silky
hair with temporal thinning, saddle nose deformity, and mildly
protruding forehead
Carney’s Complex
Carney’s complex (CNC) is a rare disease characterized by the formation of multiple endocrine and nonendocrine tumors, spotty skin pigmentation, myxomas,
and endocrine overactivity. The disease is also known
as NAME syndrome (naevi, atrial myxoma, myxoid
neurofi bromata, and freckles), and LAMB syndrome
(lentigines, atrial myxoma, mucocutaneous myxomas,
and blue naevi).
6.3 Growth Hormone Diseases 215
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CNC condition has an autosomal dominant mode of
inheritance. Carney’s syndrome is a different clinical
condition characterized by a triad of several neoplasms
including gastric epithelioid leiomyosarcoma, pulmonary chondroma, and extra-adrenal paraganglioma.
Patients with CNC are diagnosed by fulfi lling two or
more of the CNC diagnostic criteria.
Carney’s Complex Major Diagnostic Criteria
Lentiginosis and blue naevi : Lentigo is a brownish-
black fl at macule that is typically found in the lips,
around the inner canthus of the eye, axilla, or genitals
(Fig. 6.3.8 ). When the macules are found diffusely in
the body, the condition is called “lentiginosis.” The
other characteristic skin lesion found in CNC is blue
skin naevi.
Cutaneous myxomas : are seen on the trunk as small
red papules.
Cardiac myxoma : it is the most common component
of CNC. Cardiac myxoma is a gelatinous tumor, and
it is the most common primary cardiac neoplasm in
adults (50% of cardiac neoplasms). Ninety percent
of cases are seen in adult women between 30 and 60
years of age. Most cases are sporadic. Patients usually present with CNS symptoms, fatigue, arthralgia,
fever, anemia, and weight loss. Twenty percent of
myxomas are asymptomatic. Patients with CNC cardiac myxoma are younger than patients with sporadic myxoma (an average age of 24 years).
Acromegaly : CNC patients can develop acromegaly
due to GH-releasing pituitary micro-/macroadenoma.
Primary pigmented nodular adrenocortical disease
( PPNAD ): It is a rare disease of children and young
adults below 20 years of age. It can be the fi rst manifestation of CNC. Pathologically, the adrenal shows small
black, brown, red, or yellow nodules separated by atrophic adrenal cortex. Diagnosis is essentially based on
histological fi ndings. PPNAD is one of the common
causes of ACTH-independent Cushing’s syndrome.
Large-cell calcifying Sertoli cell tumor ( LCCSCT ):
bilateral germ cell tumors of the testes are the initial
presentation of CNC in 20% of cases. Diagnosis is
strengthened by the detection of high serum levels of
estrogen or androgen.
One or more of the following cancers: breast fi bro-
myxomas (25% of cases), osteochondromyxoma,
follicular thyroid carcinoma, psammomatous melanotic schwannoma.
Fig. 6.3.8. An eye and lip illustrations demonstrates the lentigo
pigmented lesions found in the inner canthus and the lips in a
patient with Carney’s complex (CNS)
Signs on US
In LCCSCT, the testes show multiple, round, well-defi ned, large
(5–10 mm) echogenic calcifi cation with acoustic shadowing
representing the stromal tumors.
Signs on MRI
Cardiac myxoma : myxoma typically appears as a heteroge-
neous mass on T2W images with a narrow base attachment
located in the interatrial septum at the area of fossa ovalis
(90% of cases). Eighty percent of myxomas arise in the left
atrium, and 10% in the right atrium. Calcifi cation is frequently
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6.3
Fig. 6.3.9. Coronal T2W testicular MR-illustration shows bilateral hypointense T2 signal intensity lesions in the testes bilaterally
representing large-cell calcifying Sertoli cell tumor (LCCSCT)
seen, and the mass shows heterogeneous contrast enhancement. The location of the tumors is very characteristic.
LCCS CT : are detected as multiple high T2 intratesticular masses
with hypointense areas representing calcifi cations (Fig. 6.3.9 ).
Sella MRI may show pituitary adenoma especially in patients
with signs of acromegaly.
PPNAD : the adrenal glands may be normal, or show limbs
macronodularity (>5 mm in size).
For Further Reading
1. Daughaday WH et al The pituitary in disorders of growth.
Dis Mon. 1962;8:1–47
2. Kaplan SA. Human growth hormone. Dis Mon. 1968;14:
1–33
3. Frohman LA. Diseases of hypothalamic releasing factors.
Dis Mon. 1976;22:1–37
4. Ron E et al Acromegaly and gastrointestinal cancer. Cancer.
1991;68:1673–77
5. Tani Y et al Locking of the metacarpophalangeal joints in a
patient with acromegaly. Skelet Radiol. 1999;28:655–7
6. Fisher MS. An unusual bone change in acromegaly. Skelet
Radiol. 1978;3:177–8
7. Doppman JL et al Cushing syndrome due to primary pigmented nodular adrenocortical disease: fi ndings at CT and
MR imaging. Radiology. 1989;172:415–20
8. Elster AD. Imaging of the sella: anatomy and pathology.
Semin Ultrasound CT MRI. 1993;14:182–94
9. Wyszynski DF. Dysmorphology in the Bible and the Talmud.
Teratology. 2001;64:221–5
10. Laron Z. Growth hormone insensitivity (Laron syndrome).
Rev Endocr Metab Disord. 2002;3:347–55
11. Laron Z. Laron syndrome (primary growth hormone resistance or insensitivity): the personal experience 1958–2003.
J Clin Endocrinol Metab. 2004;89:1031–44
12. Kornerich L et al Laron syndrome abnormalities: spinal
stenosis, Os odontoideum, degenerative changes of the
atlanto-odontoid joint, and small oropharynx. AJNR Am J
Neuroradiol. 2002;23:625–31
13. Chakraborty PP et al Laron’s syndrome in two siblings.
Indian J Pediatr. 2007;74:870–1
14. Jacobs P. Van Buchem disease. Postgrad Med J. 1977;53:
497–506
15. Boikos SA et al Pituitary pathology in patients with carney
complex: growth-hormone producing hyperplasia or
tumors and their association with other abnormalities.
Pituitary. 2006;9:203–9
16. Vandersteen A et al Cutaneous signs are important in the
diagnosis of rare neoplasia syndrome Carney complex. Eur
J Pediatr (2009);168:1401–1404
17. Mateus C et al Heterogeneity of skin manifestations in
Patients with Carney syndrome. J Am Acad Dermatol.
2008;59:801–10
18. Cazabat L et al PRKAR1A mutations in primary pigmented
nodular adrenocortical disease. Pituitary. 2006;9:211–9
19. Haupt HA. Anabolic steroids and growth hormones. Am J
Sport Med. 1993;21:468
6.4 Osteoporosis 217
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6.4
Osteoporosis
Osteoporosis is a group of disorders characterized by
reduced bone mass or density in the absence of defect
in bone mineralization. Osteoporosis can arise due to
unknown reasons (primary) or due to pathological
conditions (secondary).
Bones reach their peak density in the third decade
of life and then decrease gradually at the rate of 0.25–
1% per year. This percentage is higher in women at the
menopause, which may reach up to 8% per year.
Osteoporosis affects the axial skeleton more than the
perpendicular skeleton, while osteomalacia (excess
un-mineralized bone matrix) affects the perpendicular
skeleton more than the axial skeleton. Osteoporosis
starts to show itself on radiographs when 30–60% of
bone mass is lost.
Primary Osteoporosis
Primary osteoporosis is a term used to describe reduction in bone density in the absence of a specifi c clinical
condition that explains this bone density reduction. It
is divided into juvenile, idiopathic, and postmenopausal types.
Idiopathic juvenile osteoporosis is osteoporosis that
affects children and young adults and is typically seen
before puberty. Patients present with diffi culties and
gait abnormalities, and multiple fractures that typically
involve the metaphyses of distal tibias and the vertebral bodies. Pain in the heels and the lower back is a
common complaint. Diagnosis of this condition is
established after exclusion of all cases that may present with similar manifestations (e.g., osteogenesis
imperfecta and homocysteinuria).
Idiopathic osteoporosis is a term used to defi ne
osteoporosis seen in patients between 20 and 45 years of
age with the same clinical features as the juvenile form.
Postmenopausal osteoporosis is seen in women who
have undergone natural menopause, or after oophorectomy. Primary osteoporosis affects mainly the hip more
than any other area in the skeleton.
Vacuum phenomenon , also known as “intervertebral
cleft sign,” is a term used to describe a condition
characterized by accumulation of gas, mostly nitrogen
(95%), within the vertebral bodies, intervertebral discs,
and synovial joints. The gas is produced from the surrounding soft tissues, and its accumulation mechanism
is poorly understood. The main hypothesis of vacuum
phenomenon suggests ischemic origin. Osteonecrosis of
the vertebral endplates with negative pressure between
the bone fragments is mandatory to release gas from the
surrounding tissue, a situation that can be classically
seen in osteoporotic vertebral fractures and collapse.
Vacuum phenomenon is also seen in osteonecrosis due
to long-term corticosteroid therapy, diabetes mellitus,
arteriosclerosis, multiple myeloma, and alcoholism.
The main differential diagnosis of the intravertebral
vacuum phenomenon is gas produced by osteomyelitis
and malignancies. In infectious gaseous production,
the gas has high pressure and tends to accumulate in
small collections, plus extends into the adjacent soft
tissues, which is not seen in vacuum phenomenon
where gas is limited to the bony or intra-discal areas.
Kümmell disease is a term used to describe vacuum
phenomenon within a vertebra that arises from vertebral endplates osteonecrosis and vertebral collapse.
Kümmel’s disease represents healing failure of an
osteoporotic vertebral fracture with the formation of
pseudoarthrosis (false-joint).
Signs on Plain Radiograph and CT
Thinning of the cortex (compact bone) is the main radio-
graphic feature of osteoporosis (Fig. 6.4.1 ). It is best seen in
the second metacarpal bone diaphysis. Normally, the cortex in
the mid-shaft of the second metacarpal should be almost
one-third the thickness of the metacarpal width. This sign is
seen in up to 50% of cases.
Dowager’s Hump : osteoporotic multiple thoracic vertebrae
causing wedge deformities (Fig. 6.4.2 ).
Pathologic fractures mostly occur at the neck of the femur,
distal radius, and humeral neck.
Intracortical tunneling is a sign of rapid bone loss. It is typically
seen as long lucent lines parallel to the long axis of the bone
(Fig. 6.4.3 ). When the tunneling is severe, a double cortical
line is seen.
Diff use bone resorption occurs in 50% of cases and is
characterized by loss of the trabecular bone.
Linear translucent bands of 4–8 mm thickness are seen within
the bone in radiograph. They are commonly seen with disuse
osteoporosis and leukemic patients.
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6.4
Fig. 6.4.1. A plain radiograph of the knee shows diminished bone
mineral density (BMD) with thinning of the cortex ( arrowheads )
Fig. 6.4.2. A lateral thoracic vertebrae radiograph shows kyphosis
of the thoracic vertebrae due to osteoporosis (Dowager’s Hump)
Fig. 6.4.3. A plain radiograph of osteoporosis of the femoral
shaft demonstrates clearly the intra-cortical tunneling sign
( arrowheads )
Patchy bone resorption : seen as multiple lucent patches
usually in the carpal or tarsal bones. It can be mistaken with
lytic lesions of Ewing’s sarcoma and multiple myeloma
(Fig. 6.4.4 ).
Vacuum phenomenon is seen as a gas collection in a collapsed
vertebra or in intervertebral disc space (Fig. 6.4.5 ).
Singh index is a simple method to estimate the level bone
mineral density (BMD) on radiograph by analyzing the
changes in the trabecular pattern of the proximal femur. A
scale of six grades is classically described, with the fi rst grade
showing only basic trabecular structures (low BMD, severe
osteoporosis), and the sixth grade showing trabecular
structures in all areas of the proximal femur (high BMD,
normal bone).
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Signs on MRI
The area of vacuum phenomenon may appear as an area of
fl uid signal intensity on T2W images. This fi nding is explained
by the fact that fl uid replacement tends to fi ll the area of
vacuum gas on long supine position. This T2 fl ow signal
depends on the time of scanning. In the fi rst 10 min of the
scan, the vacuum area is seen as a hypointense area on T2W
images. The signal turns into T2 hyperintense signal between
20 and 40 min after positioning.
In Kümmel’s disease , the vertebral end plates are seen
compressing over the fractured area in fl exion. In extension,
the gap between the fractured end plates open. Intervertebral
air can be seen on CT and MRI, with no signs of infl ammation
on T2W images.
Dual Emery X-Ray Absorptiometry (DEXA) Scan
Fig. 6.4.4. Anteroposterior plain wrist radiograph in a patient
with osteoporosis shows patchy areas of radiolucent opacities
representing patchy osteoporosis ( arrowheads )
Fig. 6.4.5. Sagittal lumbar CT image in a patient with osteoporosis shows severe osteopenia, collapse of L4 vertebra (vertebra
plana), vertebroplasty of L3, with gas formation located in the
intervertebral disc space between L4 and L5 ( arrows )
DEXA scan is a quantitative method for measuring
bone mass by using low energy X-ray beam. The bone
mass is measured in units of gram per cubic centimeter
of bone. The World Health Organization (WHO)
defi nes the T -scores as follows: between +1 and −1
indicates normal bone; between −1 and −2.5 indicates
osteopenia; and osteoporosis is diagnosed when the
T -score is less than −2.5.
Pitfall : sclerosis and osteophytes in the vertebral
column can increase the values of the DEXA scan
giving a false impression of a good bone density. For
this reason, DEXA report should always be written
after comparison of the results with plain frontal and
lateral radiographs of the vertebral column to avoid
misinterpretation.
Secondary Osteoporosis
Secondary osteoporosis is seen in association with
other clinical conditions such as endocrine diseases
(e.g., Cushing’s syndrome), nutritional diseases (e.g.,
scurvy), drug-induced (e.g., heparine), neoplasms
(e.g., multiple myeloma), metabolic diseases (e.g., diabetes mellitus), and chronic infl ammatory conditions
(e.g., rheumatoid arthritis). Radiological manifestations are same as primary osteoporosis.
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6.4
Regional Migratory Osteoporosis of the Hip
(Bone Marrow Edema Syndrome)
Regional migratory osteoporosis (RMO) is a rare condition characterized by migrating arthralgia of weightbearing joints in the lower limbs (hips, knees, and
ankles).
RMO typically affects males between 50 and 60
years of age presenting with pain confi ned to a single
joint. Patients experience progressive pain in one joint
that can last from weeks to months. Peak intensity of
the pain is experienced usually in the second and third
months after the initial presentation. There is no history of trauma or signs suggesting joint infection (e.g.,
septic arthritis). The symptoms resolve spontaneously
often between 4 and 11 months after presentation.
Signs on Radiographs
Typically, there is osteopenia of the aff ected joint compared to
the other joint which normally shows no osteopenia (unless the
patient is generally osteoporotic). Unfortunately, this sign is seen
after 3–6 weeks from the start of symptoms. Remineralization of
the aff ected area may take up to 2 years to complete after the
symptoms are resolved.
Signs on MRI (Four Morphological Criteria at
T1W Images Are Needed to Indicate RMO of
the Hip)
The bone marrow edema must involve the femoral head, and
often spares the subchondral bone resulting in a thin rim of
unaff ected subchondral marrow. The edema may extend to
the femoral neck.
The bone marrow lacks the defi nite margins or transitional
zone between the lesion and the adjacent marrow.
The signal is homogeneous with areas of high- or low-
intensity foci.
The signal intensity of the marrow is moderately reduced. All
the above four criteria must be evaluated on T1W images.
Joint eff usion is seen in 75% of patients.
RMO of the knee has the same diagnostic criteria as the RMO
of the hip, and typically involves the lateral femoral condyle,
although it can aff ect any part of the knee (Fig. 6.4.6 ).
RMO Diff erential Diagnoses
Avascular necrosis : usually with history of trauma,
steroid use, chemotherapy, or renal disease. No such
history is associated with RMO. Risk factors for RMO
include low dietary calcium and tobacco smoking.
Fig. 6.4.6. Anteroposterior plain radiograph of the left knee ( a ),
with coronal T1W image ( b ), and coronal PD image ( c ) of a
57-year-old lady who presented with nonspecifi c knee pain for 3
weeks’ duration. The plain radiograph shows no signs of obvious
pathology or diminished bone density. On the MR images, the
lateral femoral condyle showed bone marrow edema signal with
no sign of a fracture of cortical destruction. The knee showed no
signs of abnormalities that explain the knee pain. The diagnosis
was regional migratory osteoporosis (RMO) of the knee and the
patient was advised a 3-month MRI follow-up examination
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Refl ex sympathetic dystrophy : there are atrophic skin
changes and history of neurological disease, which
are not seen in RMO.
Chronic recurrent multifocal osteomyelitis : has the
same picture as RMO on MRI, but plain radiographs
show both lytic and sclerotic lesions, which is not
characteristic of RMO.
For Further Reading
1. Goldring SR et al Metabolic bone disease: osteoporosis and
osteomalacia. Dis Mon. 1981;27:1–103
2. Lutwak L et al Osteoporosis. Dis Mon. 1963;9:1–39
3. Freedman BA et al Kummel disease: a not-so-rare compli-
cation of osteoporotic vertebral compression fracture. J Am
Board Fam Med. 2009;22:75–8
4. Lorenc RS. Idiopathic juvenile osteoporosis. Calcif Tissue
Int. 2002;70:395–7
5. Williamson MR et al Osteoporosis: diagnosis by plain chest
fi lm versus dual photon bone densitometry. Skelet Radiol.
1990;19:27–30
6. Aloia JF et al Risk for osteoporosis in black women. Calcif
Tissue Int. 1996;59:415–23
7. Karantanas AH. Acute bone marrow edema of the hip: role
of MR imaging. Eur Radiol. 2007;17:2225–36
8. Cahir JG et al Regional migratory osteoporosis. Eur J Radiol.
2008;67:2–10
9. Vande Berg BC et al Bone marrow edema of the femoral
head and transient osteoporosis of the hip. Eur J Radiol.
2008;67:68–77
10. Akpinar E et al The intravertebral vacuum phenomenon.
Eur J Radiol Extra. 2008;66:e55–7
11. Sarli M et al The vacuum cleft sign: an uncommon radiological sign. Osteoporos Int. 2005;16:1210–14
12. Kumpan W et al The intravertebral vacuum phenomenon.
Skelet Radiol. 1986;15:444–7
13. Libicher M et al The intravertebral vacuum phenomenon
as a specifi c sign of osteonecrosis in vertebral compression
fractures: results from a radiological and histological study.
Eur Radiol. 2007;17:2248–52
14. Hauschild O et al Evaluation of Singh index for assessment
of osteoporosis using digital radiography. Eur J Radiol.
2009;71:152–8
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6.5
6.5
Rickets and Osteomalacia
Rickets is a group of conditions characterized by accumulation of nonmineralized bony matrix (osteoid)
within the skeleton in children, while osteomalacia is
an accumulation of nonmineralized bony matrix in the
mature skeleton of adults (the bone quantity is normal,
but the bone quality is abnormal).
Understanding bone physiology and metabolism is
crucial for understanding the pathology of rickets and
osteomalacia. Bones are made up of bony cells surrounded by extra-cellular matrix. The extra-cellular
matrix has organic and inorganic components. The
organic component, also called “osteoid,” is made of
type I collagen fi bers embedded in a ground substance
composed of proteoglycans and other components.
The osteoid is secreted by the osteoblasts, and it
accounts for 35% of the bone mass. In contrast, the
inorganic component is composed of osteoid plus cal-
cium and pyrophosphate (mineral salts). The inorganic
materials are what give bone its density, and account
for 65% of the bone mass. Rickets and osteomalacia
are diseases of matrix mineralization, while osteoporosis is a disease of bony matrix.
After osteoid mineralization, the mineralized collagens are arranged in either woven or lamellar pattern.
Woven bone is immature bone with its fi bers not arranged
in any direction. Normally it presents in life as a transitional stage and then is replaced by lamellar bone.
Woven bone is not found in mature skeleton normally;
however, it is produced during healing of fractures or
remodeling (callus formation). Its presence indicates
abnormality when found in mature skeleton. Lamellar
bone , on the other hand, is mature bone with its fi bers
arranged in a certain pattern to withstand mechanical
pressure. The mature skeleton is made only of lamellar
bone, and the fi bers are arranged in vertical form in the
cortical bone and arranged in transverse form in the trabecular bone. Some sheets of lamellar bone are circumferentially arranged around a bundle of blood vessels
and lymphatics, forming what are known as “Haversian
canals or osteons.” These Haversian canals are found
in the cortical bone and arranged along the long axis of
the bone, and they communicate with each other
through channels of interstitial lamellae.
The physis is the cartilaginous growth plate in
immature skeleton which is responsible for adding
length to bone. The growth plate functions as a oneway barrier to blood vessels, allowing the blood from
epiphyseal capillaries to supply the metaphysis but not
vice versa.
Hormones that affect bone metabolism and hemostasis include the parathyroid hormone (PTH) and the
active form of vitamin D, 1,25-dihydroxyvitamin D
(1,25(HO)
calcium concentration. PTH promotes bone formation
on the physiological level, but it causes bone resorption at high concentrations. Vitamin D undergoes two
hydroxylation steps in the liver and the kidney before
it becomes metabolically active, promoting calcium
absorption from the intestines. Calcitonin is a hormone
that opposes the action of both PTH and vitamin D.
From the latter explanation of the bone metabolism,
any condition that can result in hormonal imbalance or
matrix mineralization defects can result in the development of rickets or osteomalacia. Causes of rickets
include:
Acquired rickets due to vitamin D defi ciency (most
common form).
Congenital rickets due to vitamin D enzyme hydrox-
ylation defi ciency.
Congenital rickets due to vitamin D resistance and
receptors mutation.
Congenital rickets due hypophosphatemia (low
phosphates). It can be X-linked, autosomal-dominant, or autosomal-recessive.
Acquired rickets due to hypocalcemia.
Acquired rickets due to renal failure. Reasons for
developing rickets or osteomalacia are loss of the
hydroxylation step of vitamin D and raised PTH
levels.
Patients with rickets often present with bowing of the
legs, swollen joints, bone pain, and muscle weakness.
Patients with rickets due to vitamin D resistance may
present with alopecia.
D). PTH is secreted in response to low plasma
2
D i ff erential Diagnoses and Related Diseases
Dent’s disease is a rare disease characterized by
X-linked recessive hypophosphatemic rickets, idiopathic low molecular weight proteinuria, and X-linked
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