Chapter 26: Metabolic Bone Diseases Flashcards
An elderly woman presents with a distal radius fracture. You identify reduced bone mass by a DEXA scan.
A biopsy is taken.
It is determined that the ratio of osteoid to mineralized bone is normal.
Years later, the patient develops kyphosis.
Osteoporosis - enhanced bone resorption relative to formation.
Distal radius fracture called Colles Fracture.
Kyphosis due to compression fractures of the vertebrae are called dowager’s hump.
Primary: Uncertain origin. Estrogen deficiency and aging***. Genetics (peak bone mass), calcium intake, absorption and vitamin D, exercise, environmental factors.
Causes of secondary osteoporosis include…
Side effects of drug therapy (corticosteroids, glucocorticoids),
Endocrine conditions: PTH excess. Loss of estrogen. Hyperthyroidism, hypogonbadism
Eating disorders, immobilization, marrow-related disease, disorders of GI or biliary tracts, renal disease, cancer.
An older patient presents complaining of muscle weakness, diffuse aches, and pains. A slight waddling gait is noted. A biopsy is taken and stained with the von Kossa stain. A diagnosis is made.
Osteomalacia - inadequate minearlization of newly formed bone matrix. von Kossa stain shows abnormally thick osteoid layer.
Can be due to low vitamin D.
A child presents with irritability and shortness. He has prominent frontal bones and conspicuous suture lines.
Severe dental caries and enamel defects are seen. The chest has a grossly beaded appearance of the costochondral junctions.
The sternum is curved outward.
Rickets.
Frontal bossing
Rachitic rosary
Pectus carinatum (pigeon breast)
What are the vitamin D-dependent types of rickets?
Vitamin D-dependent rickets type 1: Deficiency of renal 1 alpha hydroxylase activity. Hypocalcemia, hypophosphatemia, and high PTH.
Vitamin D-dependent rickets type II: Inherited mutations of the vitamin D receptor. Serum concentrations of vitamin D are high.
Acquired alterations in vitamin D metabolism: Defective 1-alpha hydroxylation, end organ insensitivity. Hypoparathyroidism, tumer-induced osteomalacia, chronic renal diseases.
What are renal disorders of phosphate metabolism, which interfere with vitamin D metabolism?
X-linked hypophosphatemia: Impaired transport of phosphate across luminal membrane of proximal renal tubular cells. PHEX gene.
Fanconi syndromes: Renal wasting of phosphate, glucose, bicarb, amino acid. Tubular acidosis. Wilson disease, tyrosinemia, galactosemia, glycogen storage disease, cystinosis.
Tumor-associated osteomalacia: Phosphate-wasting syndrome.
A patient prtesents with stones, bones, moans, and groans. A radiograph of the hands is shown below. An elevated PTH level is discovered, Investigation reveals a parathyroid adenoma.
Osteitis fibrosa: Primary hyperparathyroidism. Trabecular bone resorbed, marrow replaced by loose fibrosis, hemosiderin-laden macrophages, hemorrahge, woven bone.
Osteitis fibrosa cystica: Cystic degeneration of bone, osteoclast giant cells, “brown tumor”, shown below. Multiple, localized, lytic lesions.
Subperiosteal bone resorption evident in subperiosteal outer surface of the cortex - dissecting osteitis. Lamina dura of teeth can disappear.
An elderly patient presents with hypocalcemia, hyperphosphatemia, low vitamin D, and high PTH.
The spine is noted for having alternating bands of radiopaque and normally dense bone.
Combinations of osteitis fibrosa, osteomalacia, osteosclerosis, and adynamic bone disease are found.
Renal osteodystrophy.
Metastatic calcification at varius sites due to hyperphosphatemia.
Adynamic bone disease: Arrested bone remodeling. Reduction in cellular activity of the bone. See below.
A patient presents with localized bone pain. Radiograph shows “flame sign” and widespread osteolysis. Additionally, larger than normal bone is observed in the spine with a “picture frame” appearance
Biopsy shows osteoclasts with more than the usual number of nuclei and virus-like particles.
Paget disease of bone.
Picture shows cortical thickening and coarse trabeculations of the femoral head and neck.
This biopsy was taken from a person complaining of bone pain. What disease is this, and what phenomenon is imaged?
Paget’s disease of bone. Cement lines/mosaic pattern in the bone due to abnormal osteoblast activity.
Imaged is abnormal osteoclast with too many nuclei.
What are some characteristic lesions of the skull for a patient with Paget’s disease of bone?
Osteoporosis circumscripta - localized lysis in the frontal or parietal bones.
Platybasia - flattening on the base of the skull, compress medulla and upper spinal cord. Hearing loss.
Leontiasis ossea - lionlike facies due to enlargement of facial bones (especially maxillary).
In this symptom of paget’s disease of bone, patients feel lightheaded.
Pagetic steal - blood shunted from internal carotid system to bones.
A autosomal recessive storage disease involving lipids. Failure of remodeling (erlenmeyer flask shape), crisis (infarction of bone after viral illness), localized and diffuse bone loss, osteosclerotic lesions, corticomedullary osteonecrosis, pathologic spontaneous fractures, osteomyelitis and septic artheirits.
Gaucher disease.
A child presenting with disorganized mixture of fibrous and osseous elements in the medullary region of afected bones.
Radiograph is shown.
Fibrous dysplasia.
Activating mutation in the GNAS1 gene encoding alpha subunit of guanine nucleotide binding protein - increased levels of cAMP.
Radiograph shows shepherd’s crook deformity - multiple fractures over th ehears, ground-glass lucencies surrounded by reactive bone. Soap-bubble appearance.
Picture below shows histology. Loose, whorled pattern of fibroblastic tissue. Irregularly arranged, purposeless spicules of woven bone lacking osteoblastic rimming embedded in fibrous tissue.
Fibrous dysplasia presenting with endocrine dysfunction (acromegaly, Cushing, hyperthyroidism, and vitamin D-resistant rickets. Short stature.
Mccune-Albright syndrome.
Cafe au lait spots and coast of maine borders.
