Causes and Types of Dwarfism

Regents Biology 2015/2016
Mohamed M.Elsaied
2016/2017
[ Dwarfism ]

 What is Dwarfism?
Mohamed M.Elsaied
2016/2017
 Dwarfism is Hypo-secretion of Growth Hormone
 Hyposecretion (underproduction) of the Growth
Hormone during
growing years causes slow bone growth and the
epiphyseal plates
close before normal height is reached
Is short stature resulting from a particular medical condition.
An adult height of 4 feet 10 inches or under.
Dwarfism is not a disease.
There is a greater risk of some
health problems.

 Causes of Dwarfism
Mohamed M.Elsaied
2016/2017
 Reduction in GH secretion in infancy or early childhood
causes dwarfism.
 It occurs because of the following reasons:
I. Tumor of chromophobes, which compresses and
destroys the normal cells secreting GH
II. Deficiency of GH-releasing hormone secreted by
hypothalamus
III. Deficiency of somatomedin C
IV. Atrophy or degeneration of acidophilic cells in the
anterior pituitary

Mohamed M.Elsaied
2016/2017
 Pan-hypopituitarism
I. Reduction in the secretion of all the hormones of
anterior pituitary gland.
II. This type of dwarfism is associated with other
symptoms due to the deficiency of other anterior
pituitary hormones
 Chromosomal abnormalities
 Kidney disease

 Who is Affected by Dwarfism?
Mohamed M.Elsaied
2016/2017
Every one can be affected by dwarfism
One of the most common of all causes of dwarfism
is a spontaneous genetic mutation in the egg or
sperm cells.
This means while you are more likely to have
dwarfism if you have dwarf parents you can still have
it with average sized parents

 Signs and symptoms:
Mohamed M.Elsaied
2016/2017
 Primary symptom of hypopituitarism in children is the
stunted skeletal growth.
 Max height of anterior pituitary dwarf at the adult age is
only about 3 feet
 Proportions of different parts of the body are almost
normal. Only the head becomes slightly larger in relation to
the body


Mohamed M.Elsaied
2016/2017
Pituitary dwarfs do not show any deformity and their
mental activity is normal with no mental retardation
 Reproductive function is not affected, if there is only GH
deficiency.
 However, during panhypopituitarism, the dwarfs do not
obtain puberty due to the deficiency of gonadotropic
hormone.

 Classification
Mohamed M.Elsaied
2016/2017
 Dwarfism is usually caused by a genetic
variant; achondroplasia is caused by a mutation
on chromosome 4. If dwarfism is caused by a medical disorder,
the person is referred to by the underlying diagnosed disorder.
Disorders causing dwarfism are often classified by
proportionality. Disproportionate dwarfism describes disorders
that cause unusual proportions of the body parts, while
proportionate dwarfism results in a generally uniform stunting
of the body.
 Disorders that cause dwarfism may be classified according to
one of hundreds of names, which are usually permutations of
the following roots

Mohamed M.Elsaied
2016/2017
location
rhizomelic = root, e.g., bones of the upper arm or thigh
mesomelic = middle, e.g., bones of the forearm or lower
leg
acromelic = end, e.g., bones of hands and feet.
micromelic = entire limbs are shortened
source
chondro = of cartilage
osteo = of bone
spondylo = of the vertebrae
plasia = form
trophy = growth

 Dwarfism Types
Mohamed M.Elsaied
2016/2017
 Achondroplasia
 Laron dwarfism
 Psychogenic Dwarfism
Spondyloepiphyseal dysplasia congenita (SED)
 Diastrophic Dysplasia
 Campomelic Dysplasia
 dystrophia adiposogenitalis
 Hypophosphatemia
 Hallerman-Streiff Syndrome
Cartilage Hair Hypoplasia (CHH)
Robinow dwarfism/syndrome
 Turner Syndrome
 Pituitary Dwarfism

 Achondroplasia
Mohamed M.Elsaied
2016/2017
 Achondroplasia is average-size trunk and shortened upper parts of their
arms and leg
 Achondroplasia has a dominant pattern of inheritance.
80% of people with Achondroplasia have average-size parents, so the
mutation on the FGFR3 gene is new.
The remaining 20% of people with Achondroplasia
receive an altered copy from 1 or 2 affected parents.
If it inherited 2 forms they are unlikely
to live for more than a few days after birth.

 Laron dwarfism
Mohamed M.Elsaied
2016/2017
Genetic disorder, also called GH insensitivity.
It occurs due to the presence of abnormal growth hormone
secretagogue (GHS) receptors in liver.
GHS receptors become abnormal because of the mutation of genes
for the receptors.
GH secretion is normal or high.
But the hormone cannot stimulate growth because of the abnormal
GHS receptors

 Psychogenic Dwarfism
Mohamed M.Elsaied
2016/2017
Dwarfism occurs if the child is exposed to extreme emotional
deprivation or stress.
The short stature is because of deficiency of GH.
This type of dwarfism is called psychogenic dwarfism, psychosocial
dwarfism or stress dwarfism

 Dysplasia
Mohamed M.Elsaied
2016/2017
 Most types of dwarfism are known as Skeletal Dysplasias-conditions of
abnormal bone growth.
 They're divided into two types:
I. Short-Trunk :
-Those have a shortened trunk
with more average-sized limbs
II. Short-Limb:
-Those have an average-sized
trunk but shortened arms
and legs

 Spondyloepiphyseal dysplasia
Mohamed M.Elsaied
2016/2017
This genetic condition results in short stature, with adult height
usually varying from slightly under 3ft to slightly 4 ft.
Other characteristics can include clubfeet, a cleft palate, and a
barrel-chested appearance.
SED occurs approximately once in every 100,000 births.

Diastrophic Dysplasia
Mohamed M.Elsaied
2016/2017
It occurs about one in 100,000 births
First it was thought to be a different form ofAchondroplasia.
The condition is often characterized by short-limbed dwarfism and,
in some cases, cleft palate, clubfeet, hitchhiker's thumb, and ears with
a cauliflower appearance.
 Respiratory problems are sometimes present in infancy,

Diagnosis
Mohamed M.Elsaied
2016/2017
Most cases of achondroplasia can be diagnosed before birth
(through the use of an ultrasound in the later stages of pregnancy).
Ultrasounds can show shorter than average arms and legs, or whether
the baby's head is larger than average.
There are other types of dwarfism that can be diagnosed even
earlier inpregnancy and there are other types that can't be diagnosed
until after birth.
There is no cure available for dwarfism caused by genetic disorders.
Prevention and treatment of accompanying health concerns are the
only course of action available at this time for little people and their
families.

Are there Treatments for Dwarfism?
Mohamed M.Elsaied
2016/2017
Dwarfism’s treatments don't increase stature but may alleviate
problems caused by complications
Surgical procedures that may correct problems with bones in people
with disproportionate dwarfism
Some people with dwarfism elect to undergo limb-lengthening
surgery.
Growth hormone deficiency is treated with injections of a synthetic
version of the hormone.

 Reference
Mohamed M.Elsaied
2016/2017
 Little People of America. (2005, June 28). What is Dwarfism?
Retrieved from
http://www.pbs.org/pov/bigenough/special_dwarfism.php
 Mayo Clinic Staff. (2011, August 27). Dwarfism . Retrieved from
http://www.mayoclinic.com/health/dwarfism/DS01012
 A.D.A.M Medical (2011). Growth hormone deficiency-children In N.
Kaneishiro K. & D. Zieve (Eds.), PubMed Health MD: National Center for
Biotechnology Information,. Retrieved from
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002159/
 Seattle Children's Hospital, Research & Foundation.. "Dwarfism and
Bone Dysplasias".

Causes and Types of Dwarfism

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