Bone Pathologies

Achondroplasia

Most common form of dwarfism. Caused by a failure of endochondral ossification (longitudinal growth at growth plates). This is caused by a gain of function mutation at FGFR3, which inhibits chondrocyte proliferation.

Symptoms include shortened extremities or limbs, macrocephaly (enlagred head) trident hand, and frontal bossing

macrocephaly

enlarged head; because bones in the head use membranous ossification so

aren’t affected

chondrocyte

cell that makes cartilage by secreting collagen and proteoglucans

Chondrosarcoma

malignant cartilage tumor. most often seen in males between 30-60 years if age in the pelvis and thoratic cage. Treatments are surgery and chemo.

Ewing Sarcoma

Malignant cells in the bone, possibly from mesenchymal stem cells. most often found in the diaphysis of long bones like the femur. Common in caucasian boys under 15.

Hypoparathyroidism

Decreased levels of parathyroid hormone. Can be casued by the excision of parathyroid glands, DiGeorge Syndrome, autoimmune destruction, or hypomagnesia. Symptoms are mostly muscular due to serum hypocalcemia. These include tetany. Symptoms also include Chvostek’s Sign and Trousseau sign. Treatments are PTH, calcium/vitamin D supplementation.

DiGeorge Syndrome

chromosomal defect which includes the congenital absence

of parathyroid glands

Tetany

involuntary muscle contraction

Lamellar Bone

More mature bone than woven bone, the collagen fibers have parallel organization into sheets which provide mechanical strength to the bone.

Osteoarthritis

Mechanical wear and tear destroys articular cartilage. As the articular cartilage gets worn away, bone con grinding against bone, activating bone remodeling and resulting in osteophytes. X-ray can show decrease of particular cartilage and bones for formation. Symptoms include pain in weight-bearing joints improved with rest.

osteophyte

bone spur

Osteoblastoma

benign but aggressive bone tumor that arises from osteoblasts. The most common area of origination occurs in vertebrate. Tumors larger in size >2cm are resistant to NASID. May cause neurological conditions if touching the spinal cord

Osteochondroma

Most common benign primary bone tumor. Most affected demographic is males under 25. This condition is the lateral projection of growthplate into the metaphysis of the long bone. Presents as a painless mass and is most often not treated.

Osteoid osteoma

Benign primary bone tumor that occurs in the cortex of long bones that arises from osteoblasts. Most affect males under 25. Focal bone pain that worsens at night and is relived by NSAIDS. Radiography will show a bone mass <2cm.

Osteoma

Benign primary bone tumor that occurs on the surface of facial bones. Most effects those in middle age with Gardner Syndrome.

Osteomalacia

Defective mineralization of bone. Most commonly caused by vitamin D deficiency. In adults this can be caused by malabsorption of vitamin D, poor dietary vitamin D intake or lack of sun exposure, or decrease in 1,25 dihydroxyvitamin D synthesis. Symptoms can include bone and joint pain, fractures, difficulty walking. X rays show decreased bone density. Serum blood labs show decreased serum phosphate, decreased serum calcium, increased serum alkaline phosphetase, and increased parathyroid hormone. Treatment is vitamin D supplementation.

Rickets

Defective mineralization of bone in children due to a vitamin D deficiency.

Osteonecrosis

Reduced BF to the bone leads to infarction of the associated bone and bone marrow. Often very painful. The femoral head is the most common area due to insufficiency of the medial circumflex femoral artery. This leads to severe hip pain and difficulty walking.

Risk factors include corticosteroids, alcoholism, sickle cell disease, trauma, the bends (as occurs in divers), Legg-Calve-Perthes disease [idiopathic], Gaucher disease, Slipped capital femoral epiphyses [CAST Bent LEGS]

Osteopetrosis

Failure of normal bone resorption due to defective osteoclast activity where the osteoclast cant adequately acidify the bone matrix to activate the collagenases/proteases. The activated osteoclasts will continue to release TGFB to activate osteoblasts. This causes the bone to thicken. These thickened and dense bones are highly susceptible to fracture. This can lead to pancytopenia, leading to sever anemia, easy bleeding and bruising, and frequent infections. This can also lead to cranial nerve impingement and palsies due to narrow foramina.

Pancytopenia

Decrease in RBC, WBC, and platelets due to a loss or problem in bone marrow

Osteoporosis

decrease in bone mass leading to increased risk of fractures. These are most commonly due to an increase in bone resorption due to a decrease in estrogen levels and old age or drugs. Diagnosed by a bone mineral density measurement via a DEXA scan. One time screening is recomended for women over 65. Treatment includes bisphosphonates, denosumab, and calcitonin

Osteosarcoma

Malignant primary bonetumor from osteoblasts and accounts for 20% of primary bone tumors. peak insidence is in males younger than 20 YO. Occurs in metaphysis of long bones especially in knee region. Painful and large mass. Treatment is surgery and chemotherapy.

Paget Disease of the Bone

Localized disorder of abnormal bone remodeling. There is a dramatic increase in osteoclast activity followed by osteoblast activity that forms poor quality woven bone. If in a long bone can cause bowing deformity or if in the skull can cause narrowing of auditory foramen leading to hearing loss. Treatment is bisphosphonates.

Primary hyperparathyroidism

increase in parathyroid hormone due to parathyroid adenoma or hyperplasia. Causes hypercalcemia, hypercaalcuria, polyuria, hypophospjatemia, increased ALP, decreased bone density, and neuropsychiatric disturbances. [Moans groans, stones, thrones, and psychiatric overtones.

genu varum

pathological bow in the legs due to rickets/vitamin D shortage

craniotabes

soft skull

rachitic rosary

enlarged costochondral joint

secondary hyperparathyroidism

Increase in parathyroid hormone due to a problem somewhere other than the actual parathyroid gland. Most often due to chronic renal disease causing a decrease in vitamin D (and therefore a decrease in serum calcium levels). Parathyroid reacts by increasing PTH release to try to normalize calcium levels. Blood tests will show hypocalcemia, hyperphosphatemia, and increased ALP. Bone density will decrease due to constant activation of osteoclasts

Woven Bone

Primary bone, immature bone found in the embryo, newborn, and during healing of a bone fracture. The collagen fibers are irregular as osteoblasts quickly lay it down, so the bone is mechanically weak. Presence is always abnormal in adults unless its early in a bone fracture