Pathoma Flashcards
What is achondroplasia and what is it caused by?
Impaired proliferation in the growth plate; common cause of dwarfism. Due to an activating mutation in the FGFR3.
Describe the extremities of a patient with achondroplasia?
They will have a normal head and chest, but shortened extremities
What is endochondral bone formation? What bones use this for growth?
Formation of a cartilage matrix which is then replaced by bone; used by long bones
What is intramembranous ossification? What bones use this for growth?
Characterized by formation of bone without a preexisting cartilage network. Flat bones develop this way (skull and ribs)
What is the reason for shortened extremities and not skull bones in patients with achondroplasia?
Long bones use endochondral ossification to develop. The mutation in FGFR3 causes impaired proliferation of cartilage leading to shortened bones.
What is osteogenesis imperfecta and what is the cause of it?
Congenital defect of bone formation resulting in structurally weak bone. Defect in type 1 collage synthesis.
What are some of the clinical features of osteogenesis imperfecta?
Multiple bone fractures - can mimic child abuse
Blue sclera - thinning of scleral collagen revealing underlying chorocoidal veins
Hearing loss - bones of the middle ear fracture easily
What is osteopetrosis and what is the cause of it?
Inherited defect of bone reabsorption resulting in abnormally thick heavy bone that fractures easily.
Due to a defect in osteoclast function. Carbonic anhydrase II deficiency also does not allow for an acidic environment.
What are the clinical features of of osteopetrosis?
Bone fractures
Anemia - due to bony replacement of the marrow
What is the treatment of osteopetrosis?
Bone marrow replacement because osteoclasts are derived from monocytes
What is Rickets/Osteomalacia and what causes it?
Defective mineralization of osteoid - osteoblasts produce osteoid which is then mineralized with calcium and phosphate.
Usually due to a deficiency of Vitamin D
How does Vitamin D act to raise serum calcium?
Intestine - increases absorption of calcium and phosphate
Kidney - increases absorption of calcium and phosphate
Bone - increases absorption of calcium and phosphate
Rickets usually presents in what age group and what are the symptoms?
Arising in children less than 1 year old
Pigeon-breast deformity
Frontal bossing (enlarged forehead) due to osteoid deposition on the skull
Rachitic rosary - due to osteoid deposition at the chostochondral junction - bone bumps on rib cage
Bowing of the legs
Osteomalacia is due to? What can it lead to?
Low vitamin D in adults - inadequate mineralization results in weak bone with an increased risk for fracture
What are the lab findings associated with osteomalacia?
Decreased serum calcium, decreased serum phosphate, increased PTH, and increased alk phos (due to osteoblasts trying to mineralize)
What is osteoporosis and what can it lead to?
This is a reduction in trabecular bone mass and can result in porous bone with an increased risk for fracture
What factors can affect peak bone mass and the rate of decline through life?
Peak bone mass is determined by - exercise, genetics, and diet
The rate can change based on diet and and exercise
What are the clinical features of osteoporosis?
Bone pain and fractures in weight-bearing areas such as vertebrae, hip and distal radius
Bone density is done using a DEXA scan
Calcium, phosphate, PTH and alk phos are all normal
What is the treatment of osteoporosis?
Diet, exercise, Vitamin D
Bisphosphonates - induce apoptosis of osteoclasts
What is Paget’s disease and what is the cause of it?
This is an imbalance between the osteoblasts and osteoclasts - leading to the osteoblast essentially going crazy
A biopsy of a person with Paget’s Disease will reveal?
Mosaic Pattern of Lamellar Bone
Cement lines
What are the clinical features of Paget Disease of the bone?
Bone pain due to microfractures
Increased hat size - skull is most often affected
Isolated elevated alk phos - mineralization of bone
What is the main complication associated with Paget Disease of the bone?
Osteosarcoma
What is osteomyelitis?
Infection of the marrow and bone
What are the most common causes of osteomyelitis?
Transient bacteremia (children) seeding the metaphysis Open-wound bacteremia (adults) seeds epiphysis
What are the most common agents for osteomyelitis?
S. aureus - most cases >90%
N gonorrhoeae - sexually active young adults
Salmonella - sickle cell disease
What are the clinical features of Osteomyelitis?
Bone pain with signs of infection
Lytic focus surrounded by sclerosis of bone on x-ray
What is Avascular Necrosis? What is the cause?
Ischemic necrosis of bone and bone marrow
Causes include trauma or fracture
What is a major risk factor of avascular necrosis?
Osteoarthritis
What is an Osteoma and where does it arise?
Benign tumor bone - most commonly on facial bones
Associated with Gardner Syndrome - FAP and Fibromatosis
What are the characteristics of an Osteoid osteoma?
Benign tumor of osteoblasts (producing osteoid) surrounded by a rim of reactive bone.
Occurs in young adults
Arises in the cortex of long bones.
What is important about the type of pain that is associated with osteoid osteoma?
Presents as bone pain that is relieved with asprin - decreased prostaglandins
How does an osteoblastoma differ from an osteoid osteoma?
Arises in the vertebrae and present as bone pain that does not respond to asprin
What is an osteochondroma?
This is a tumor of bone with an overlying cartilage cap. It arises from a lateral projection of the growth plate; bone is continuous with the marrow space
What are the characteristics of an osteosarcoma?
Malignant proliferation of osteoblasts - arises in the metaphysis of long bones usually in the distal femur or proximal tibia
Peak incidence is seen in teenagers - less common in elderly
What are the risk factors of osteosarcoma?
Familial retinoblastoma
Paget disease - osteosarcoma in elderly
radiation exposure
What is the important X-ray finding associated with Osteosarcoma?
Imaging reveals sunburst appearance and lifting of the periosteum - Codman Triangle
What is a giant cell tumor?
Tumor comprised of multinucleated giant cells and stromal cells
Arises from the epiphyseal plate - only tumor to do so
Soap Bubble appearance on X-ray
What is a Ewing Sarcoma?
Malignant proliferation of poorly-differentiated cells from neuroectoderm
Diaphysis of long bones
What is the important genetic component of Ewing Sarcoma?
11;22 translocation
What are the characteristics of a Chondroma?
Benign tumor of cartilage and usually arises from the small bones of the hand and feet
What are the characteristics of a Chondrosarcoma?
Malignant cartilage-forming tumor that arises in the medulla of the pelvis or central skeleton
What are the characteristics of metastatic tumors of the bones?
These are more common than primary bone tumors
These usually result in osteolytic lesions
Prostatic carcinoma usually produces osteoblastic lesions