19- Disorders of Growth/Development Flashcards
What is dysplasia?
a condition affecting growth or development in which the primary defect is intrinsic to the affected tissue
What is dysostosis?
condition of abnormal cartilage ossification or bone remodeling. Usually only a single bone or group of bone involved
What is dystrophy?
condition resulting from defective or faulty nutrition, broadly constructed to include nourishment of tissue by all essential substances including those normally manufactured by body itself
What are the 2 extrinsic factors that can affect fetal cartilage?
hormonal abnormalilites, metabolic disturbances
At what height is dwarfism in males and females?
Males < 58in, Females < third percentile for age
What is proportionate dwarfism?
short stature where BOTH trunk and extremities are EQUALLY affected
What is disproportionate dwarfism?
extremities are relatively affected more or less than trunk
What is rhizomelia?
proximal segments are disproportionately shorter than middle and distal segments
What is mesomelia?
middle segments are disproportionately shorter than proximal and distal segments
What is acromelia?
distal segments are disproportionately shorter than proximal segments
What is micromelia?
shortness of limb
What would happen if there are problems with intramembranous ossification?
Abnormalities seen in patients with cleidocranial dysplasis
I) Cranial facial abnormalities
II) no clavicle
What is the etiology of DMD?
disruption of muscle cell membrane physiology which results in abnormal muscle function
What is the predominant ECM component of bone, tendon and ligament?
type I
What is the morphology of collagen?
triple helix
What are the genetic defects to cause osteogenesis imperfecta?
transcription, translation, hydroxylation, glycosylation, cross linking, extracellular transport, cleavage of procollagen
What are the etiologies of short stature?
A)Malnutrition
B) endocrinopathy
C) Skeletal dysplasia
D) Constitutional short stature
Why is family Hx important for pt’s with skeletal dysplasias?
Many skeletal dysplation are caused by genetic mutation transmitted by mendelian patterns of inheritance
What is the incidence of achondroplasia?
A) 1.5 per 10,000 live birth
B) Most common form of dwarfism
What are the physical characteristics of achondroplasia?
avg height of 48 in, short extremities but normal size trunk because of FGFR3 active mutation which stunts endochondral ossification, trident hands, bowlegs common, large head, hyperlordosis
What is the trident hand of achondroplasia?
in full extension the bases of the digits can touch but the distal tips cannot
Why do achondroplasia pt’s have a waddling gait?
) Being bow legged (genu varum)
II)Loss of full hip extension
What are the Sx of spinal stenosis?
A)low back pain,
B) lower extremity paresthesias,
C)weakness,
D) neurogenic claudication (leg pain).
What shows on the radiographs of the long bones of achondroplasia?
short, metaphyseal flaring, prominent muscle insertion sites, distal femoral physis has a characteristic inverted V appearance, long fibula, broad pelvis, shortening of the base of the skull
Why ican surgery be a way to treat spinal stenosis in achondroplasia pts?
Surgical spinal decompression with laminectomy with or without spinal fusion is often necessary for symptomatic relief
How can surgery treat some achondroplasia pt’s knee pain?
I)bony realignment procedures (osteotomies)
II)growth plate arrest (epiphyseodeses)
What is the cause of DMD?
A)X-linked recessive disorder
B)characterized by progressive loss of muscle function
C) replacement of normal muscle by fibrous and fatty tissue.
Why do muscle cells die in DMD pt’s?
lack of dystrophin results in:
I)cell membrane fragility
II)leakage of intracellular contents into the ECM (clinically manifest by increased serum creatine kinase levels)
III)decreased synthesis of dystrophin-associated proteins
What is dystrophin?
a cell membrane protein that stabilizes the muscle cell membrane and links the cytoskeleton to the ECM.
What is the clinical presentation of DMD?
A)Normal skeletal muscle at birth
B)Delayed walking, abnormal gait, and clumsiness
C)Later stages include: walk with a wide based gait, inability to run or maneuver stairs in a reciprocal fashion
D)Pseudohypertrophy of the calves by ages 3-4
What are myopathies?
Myopathies are characterized by functional but not progressive abnormalities
What are muscular dystrophies?
Muscular dystrophies are disorder of progressive muscle deterioration
What is the presentation of DMD at birth?
I)Patients have normal skeletal muscle at birth, over time, this tissue is replaced with fibrofatty tissue
II)Patients present well after birth
III)Parents will report delayed walking, abnormal gait, and clumsiness
What is the presentation of DMD at 18 mo?
Any boy who is unable to ambulate should be screened for Duchenne muscular dystrophy by measuring serum creatine kinase levels
What is the presentation of DMD at 3-4 yrs?
I)By the age of 3-4 years, patients will demonstrate characteristic pseudohypertrophy of the calves which is caused by the replacement of muscle with fibrofatty tissue.
II)Lumbar lordosis can also be quite pronounced
III)The most characteristic clinical feature is Gower’s maneuver(Obj 31)
What is the Growers maneuver?
I) patients will roll prone
II)rise on all four limbs
III) extend the lower extremities
IV walk their hands along the floor and up their legs until they are standing upright
How can corticosteroids treat DMD?
can improve muscle strength and reduce loss of strength over time
What is a good way to prevent and preserve for Tx of DMD?
Musculoskeletal care like heel cord stretching, strengthening and bracing
When does DMD pts lose the ability to walk?
2nd decade
What indicated for any patient with Duchenne muscular dystrophy and a spinal curvature of greater than 20°?
Spinal fusion
What is Osteogenesis imperfecta (OI)?
is a hereditary disorder of connective tissue caused by mutations in the gene for type I collagen
What is mutated to cause OI?
I) Significant number of case also due to new genetic mutation
C)OA results from mutation in the genes encoding type I collagen COL1A1 and COL1A2
I) Genes encode for the procollagen triple helix
II) mutations affects the quality and quantity of the procollagen molecules
a) which in turn affects the production of Type I collagen
What is Type I OI?
the most common form and the mildest clinical manifestations
I)Inheritance pattern is autosomal dominant
II)Patients with type I OI have blue sclerae, exhbit long bone fractures after walking age, and have normal stature and life expectancy
What is Type II OI?
the lethal form
I)Autosomal recessive inheritance
II)Affected individuals are stillborn or die within the first weeks of life, usually because of respiratory failure or intracranial hemorrhage
III)Multiple rib and long bone fractures are seen and sclerae are blue
What is Type III OI?
a severe non-lethal form
I)Most cases are autosomal dominant
II)Sclerae are of normal color but multiple fractures are seen at birth
III)Stature is short and life expectancy is reduced with respiratory failure, intracranial hemorrhage and basilar invagination accounting for premature mortality
What is Type IV OI?
the intermediate form, most rare
I)Sclerae are normal, adult height is variably affected
II)Abnormal dentition and bony fractures are common
III)Life expectancy varies depending on severity of the disease
How is OI managed?
A)Treatment remains primarily supportive, with an emphasis on injury and prevention and maximizing function
B)Fracture treatment should be as minimally debilitating as possible
C) Most treatment is by non surgical means because patient still has capacity to heal
D)Use of braces, supportive devices, and physical therapy is encouraged during recovery, both for bony healing, and further injury prevention
E) Surgical treatment reserved for patients over the age 5
F)Scoliosis is treated by surgical means
I) arthrodesis for progressive spinal curves or curves greater than 40o
