PATHOLOGIES OF THE MUSCULOSKELETAL SYSTEM
I. Diseases of Bone Framework
Disease Etiology Clinical Features
OSTEOPOROSIS a group of diseases charac by a ↓ in bone Immobilization: confinement to bed > 6 months
mass resulting in vulnerability to loss of 30% of initial bone. Lack of exercise leads
fracture. Mostly a consequence of to ↑ in bone resorption and ↑ bone formation.
aging, part. in post-menopausal Other: can occur in Cushings Syndrome,
women. hypogonadism, hyperthyroid, hypopituitary,
MORPH: Cortex ↓ thickness pregnancy and lactation, malabsorption,
Trabeculae of cancellous bone ↓ in malnutrition, prolonged admin of heparin
number and size. Bone mineralization is Clinical: bone pain, deformity, height loss,
normal and osteoid seams are normal fractures of femoral neck and vertebrae
width. Common in vertebrae, femoral Diagnosis: XRay with thin cortices. Osteopenia or
neck, wrist. “little bone” seen in osteomalcia, OI, osteitis
Aging: most imp. factor, esp > 40-50 fibrosa, renal osteodys, multiple myeloma. Serum
when mass decreases at a faster rate Ca2+ and PO4- normal.
and more pronounced in women. Cause Estrogen replacement, exercise, and Ca2+ help ↓
of ↓ mass and ↑ osteoclastic resorption risks.
is unknown. Ca2+ absorption also ↓
with aging.
↓ Estrogenic activity post-menopause:
↑ loss of cortical bone in post-
menopausal and post-oophorectomy.
For men, androgen deficiency is imp.
RICKETS Vit. D deficiency or PO4- depletion in CLINICAL: pain, bone deform including rachitic
children. Can result from dietary rosary (swollen costochondral jxn of ribs), outward
deprivation, fat malabsorption, curvature of sternum (pigeon chest), shortened and
prolonged lack of sunlight, chronic renal deformed limbs with severe bowing of arms and
failure. PO4- depletion can occur from legs, freq. fxs.
Fanconi syndrome, heavy metal XRAY: thickened, irreg. and Lobulated epiphyseal
poisoining, idiopathic PO4- leak. plate
MORPH: defective mineralization of
osteoid wide osteoid seams and a
decrease in calcified bone.
OSTEOMALACIA Vit. D deficiency or PO4- depletion in CLINICAL: In dietary Vit D deficiency, serum levels
(Soft Bones) adults. Can result from dietary of Ca2+ and PO3 are low due to diminished
deprivation, fat malabsorption, absorption, esp. of Ca2+. Low Ca2+ stimulates
prolonged lack of sunlight, chronic renal Parathyroid glands Secondary HyperPTH
failure. PO4- depletion can occur from XRAY: osteopenic patten with compression fxs,
Fanconi syndrome, heavy metal decreased in bone thickness.
poisoining, idiopathic PO4- leak.
MORPH: defective mineralization of
osteoid wide osteoid seams and a
decrease in calcified bone.
OSTEITIS FIBROSA “von Recklinghausen Disease” XRay shows “moth-eaten” in phalanges and
CYSTICA ↑ parathyroid hormone mobilizes Ca2+ clavicles.
(Hyperparathyroidism) from bone ↑ osteoclastic activity Tumor like masses with giant cells, cysts,
subsequent fibrous replacement. hemorrhages, and fibrous tissue Brown Tumors
↑ resorption and fibrosis formation of reparative giant cell granulomas.
cysts and areas of hemorr.
RENAL Changes include: osteitis fibrosa May be osteosclerosis if severe
OSTEODYSTROPHY cystica, osteomalacia, osteoporosis
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Disease Etiology Clinical Features
PAGET DISEASE disease of uncertain etiology assoc. with AGE: 40-60, most common in Caucasians
(Osteitis Deformans) irreg. thickening and softening of MICRO: Osteolytic stage resorption with
bones. increased osteoclasts Mixed Stage new bone
ETIOLOGY: paramyxovirus infection formation with abundant osteoblasts. Bone
suggested, but not proven. Polyostotic haphazardly laid down mostly as woven bone, some
85% and monostotic 14% of cases converted to lamellar. Mosaic Pattern:
STAGES: 1) Initial Osteolytic: bone minerlization lags and newly laid down bone well
resorption by osteoclasts 2) Mixed demarcated by osteoid seams or cement lines.
Osteolytic-osteoblastic: woven bone Marrow spaces filled with loose, vascular connective
with mosaic pattern 3) Burnt-out, tissue Osteosclerotic Stage predom. bone
quiescent Osteosclerotic formation and osteosclerosis
MACRO: most common in spine, pelvis, CLINICAL: Initially, bone pain, fxs, deformities.
femur, skull, tibia, humerus. Deafness common when skull affected. Vertebral
Spine thickening and softening of compression with height distortion. Coarsening of
resulting in kyphosis, shortening of trunk facial bones leontiassi ossea (lion-like) Serum
and pressure on nerves in vertebral ALP markedly ↑. Can have high output cardiac
foramina. Skull prog. ↑ in size due to failure in polyostotic cases. Osteosarcoma may
thickening, the base may be involved dev. in 1%
with pressure in nerves. Femur ↑ XRAY: bone lysis and reformation
thickness with coax vera and anterior
bowing.
FIBROUS DYSPLASIA benign replacement of bone by disorg Albright Syndrome: 5% most commonly in
fibrous and osseus elements. Occurs in precocious puberty in females. Other endocrine
children or adults and may be problems include acromegaly, Cushings Syndrome,
monostotic. Polyostotic assocl with skin hyperthyroid. Skin Lesions: pigmented macules
pigmentation and endocrine problems. (Café au lait spots) usually over buttocks, back,
Monostotic FD: most common (70%) sacrum.
and most common in prox femur, tibia, XRAY: lucent ground glass appearance with well-
ribs, facial bones. Can lead to marginated borders and thin cortex
pathologic fx. MICRO: benign fibroblastic tissue in a whorled
Polyostotic FD: 25% usually in children pattern with haphazardly arranced trabeculae of
with pthologic fxs, limb deformities, woven bone which lack osteblastic rimming and
limb length discrepancies. Most common form configurations likened to Chinese charac.
in females. RARELY, sarcomas may arise.
Serum ALP elevated. Ca2+ and PO4- normal.
NONOSSIFYING non-neoplastic developmental lesion in MICRO: cellular fibroblastic tissue with scattered
FIBROMA children most commonly in femur, tibia, lipid-laden Macros and multinucleated giant cells.
(Fibrous Cortical and fibula. Well-demarcated, CLINICAL: extremely common, usually asx and
Defect) radiolucent defects of cortex with thin often disappears spontaneously within years. NO
intact layer of subperiosteal cortical TX to sarcomas.
bone.
HYPERTROPHIC periosteal new bone formation, arthritis, New bone formation distal ends of long bones,
OSTEOARTHROPATHY clubbing of digits usually in pts with metatarsals, metacarpals, and prox phalanges.
bronchial CA, pleural tumors, Arthritis adjacent joints and is nonspecific with
pulmonary METS, mediastinal Hodgkins, edematous thickening of synovium and mild
Chronic Lung Infections, Chronic Liver lymphoplasmacytic infiltrate
Dz. Clubbing edematous fibrovascular overgrowth in
Clubbing alone may occur secondary to tips of digits and appears dusky to cyanotic.
same conditions but also with cyanotic Resection of underlying CA reverses changes.
heart disease, infective endocarditis,
UC, Crohns, CA of Eso and Colon.
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