Download Snímek 1

Musculoskeletal Pathology
Part II
Joints, Tendons, Tendon Sheaths, Bursae & Muscles
Joint diseases
Congenital defects
Dysplasia coxae congenita
Trauma
Degenerative diseases
Osteoarthritis
Inflammation
Infective arthritis
Lyme disease
Tuberculous arthritis
Rheumatoid arthritis
Gout
Tumours
Pigmented villonodular synovitis
Dysplasia coxae congenita
autosomal recessive congenital disorder
hypoplasia of hip joint with congenital subluxation or luxation
if left untreated → early secondary osteoarthritis
Trauma
disruption of synovial membrane – bleeding into the join cavity
(haemarthros)
organization of haematoma – fibrous adhaesions limiting joint movements or
ankylosis (joint space replaced by metaplastic bone)
haemarthros often complicates disorders of coagulation (haemophilia)
Osteoarthritis
most common of the joint diseases (14% of adult population)
primary process is breakdown of the articular cartilage
weight-bearing joints affected (hip, knee, intervertebral joints)
Clinical features: pain, joint deformity, limitation of movement, crepitus
(creaking sound heard on movement of the joint)
Radiographic features: narrowing of joint space
Two main groups:
Primary OA: no known associated condition
Secondary OA: degeneration of previously damaged joint (congenital
disorders, inflammation, trauma)
Morphology
erosive changes of joint cartilage („fibrillation“), flaking off of small portions
of cartilage, later complete loss of cartilage – polishing of the denuded bone
(smooth ivory-like surface)
thickening of subchondral bone plate, synovial fluid under pressure enters
into small defects in the bone → subchondral pseudocysts
bony outgrowths at the margins of the articular cartilage (osteophytes)
Infective arthritis
Staphylococcus aureus, Neisseria gonorrhoeae
blood spread (most common), direct penetration (trauma) and direct
spread from a contiguous infected site (osteomyelitis)
hyperaemia and acute inflammatory infiltrate in the synovial membrane,
exudate accumulation in the joint cavity (pyarthros)
lysosomal enzymes released from neutrophils → severe damage of the
articular cartilage – secondary osteoarthritis
Lyme disease
spirochaete Borrelia burgdorferi transmitted to humans via tick bites
systemic disease: skin, nervous system heart, joints
Stage I: macular skin lesion (erythema migrans) + low-grade fever,
headache, arthralgia, muscle pain, enlargement of regional lymph nodes
Stage II: early bloodstream dissemination of borrelia: nervous system
(meningitis, meningoencephalitis, neuritis), heart (atrioventricular block,
pericarditis)
Stage III: chronic disease (M or Y after the initial infection): arthritis (large
joints, similar to rheumatoid arthritis), nervous system (encephalopathy),
skin (acrodermatitis chronica atrophicans Herxheimer)
Tuberculous arthritis
children, haematogeneous dissemination
knee, hip, elbow and ankle
insidious development of pain, swelling and limitation of movement, other
signs of inflammation mild or absent
synovial hyperplasia, tuberculous granulomas in 90% of cases, acid-fast
bacilli seldom identified
Rheumatoid arthritis
common multisystem autoimmune disease
three times as common in premenopausal women as in males
small joints of the hands and feet, knees, hips, involvement frequently
symmetrical
rheumatoid factor (IgM) positive in 95%
complication: secondary amyloidosis
Morphology
hyperplasia of synovial membrane with increased vascularity,
cellularity and synovial fluid production
inflammatory infiltrate (lymphocytes and plasma cells), lymphoid
follicles
pannus (proliferation of inflammed hypervascular granulation tissue)
degradation of articular cartilage, fibrous adhesions → joint movement
severely limited, sometimes ankylosis (metaplastic bone), osteoporosis
of adjacent bone
deformities of joints (ulnar deviation of the fingers)
periarticular rheumatoid nodules in 30% (central area of fibrinoid
necrosis surrounded by macrophages and fibroblasts arranged in a
palisaded fashion)
Variants of RA:
Juvenile rheumatoid arthritis (JRA): individuals younger than 16 years,
large joints predominantly involved, rheumatoid factor often negative
Still’s disease (systemic JRA): fever, leucocytosis, enlargement of liver,
spleen and lymph nodes
Felty’s syndrome: RA + splenomegaly + neutropenia
Gout
disorder of purine metabolism → hyperuricaemia
30 – 60 years, male preponderance
deposition of monosodium urate crystals into articular cartilage, synovial
membrane and periarticular soft tissues (tophi, tophaceous gout)
Acute gouty arthritis: metatarsophalangeal joint of the big toe (70%),
ankle, knee, wrist, elbow, the affected joint is red, hot, swollen, very painful
and tender
Chronic gouty arthritis: follows recurrent episodes of acute gouty arthritis,
progressive erosion of cartilage and bone – limited joint function
Pigmented villonodular synovitis
benign tumour rather than inflammatory condition
knee joint (80%)
mild pain, swelling, tenderness
brown-coloured nodular thickening of synovial membrane
villous synovial hyperplasia
diffuse proliferation of mononuclear cells resembling histiocytes
various number of osteoclast-like multinuclear giant cells
depositions of hemosiderin
Diseases of tendons, tendon sheaths and bursae
Ganglion
area of myxoid degeneration of connective tissue of tendon sheath
extensor surfaces of hand and feet
thin walled pseudocyst containing mucoid fluid
Tendovaginitis (inflammation of the tendon sheath)
purulent, rheumatoid (serofibrinous), tuberculous
Tendovaginitis stenosans (deQuervain): stenosis of the tendon sheath by
accumulation of fibrocartilaginous tissue – discontinual movement of the affected
finger (digitus saltans)
Bursitis
bursae around shoulder, elbow and knee
Acute bursitis (mechanical overload): serofibrinous exudate
Chronic bursitis (repeated traumatisation): fibrous thickening of the wall,
hyperplasia of synovial lining and fibrin deposits
Diseases of skeletal muscle
Muscle atrophy
Muscle dystrophy
Myasthenia gravis
Inflammatory disorders (myositis)
Muscle atrophy
Generalized: malnutrition, hypopituitarism, immobilisation
Localized: immobilisation of one limb, denervation (trauma, neuritis,
poliomyelitis)
Microscopic features: decrease in size of muscle fibers
Muscle dystrophy
heterogeneous group of genetically determined disorders
spontaneous progressive degeneration of muscle fibers
microscopic features: different size of muscle fibers (combination of
atrophy and hypertrophy), degenerative changes (fragmentation of the
sarcoplasma, necrosis), signs of regeneration (cells with basophilic
cytoplasm and more nuclei), fibrosis, later lipomatosis
Duchenne-type dystrophy:
X-linked recessive disorder – males affected only
lack of dystrophin (immunohistochemistry)
early childhood (5 years), pelvifemoral groups of muscles (frequent falls,
gait disturbances, difficulty in rising), progress to other muscle groups
(wheelchair bound between the ages of 10 to 12 years), death usually
before the age of 20 years (respiratory difficulties, pneumonia)
Becker-type dystrophy:
similar to the Duchenne-type dystrophy, but much milder clinical picture
dystrophin is produced, but is abnormal
Dystrophia myotonica:
autosomal dominant disorder
after the age of 20 years, sometimes congenital
clinical features: myotonia (prolongation of muscle contraction after
voluntary effort has ceased), muscle weakness (facial muscles, distal
muscle groups)
multisystemic disease: frontal baldness, cataract, cardiomyopathy,
dementia, gonadal atrophy)
Myasthenia gravis
acquired autoimmune disorder: autoantibodies against acetylcholine
receptors on the motor endplate → defect of neuromuscular transmission
hyperplasia of thymus (60%), thymoma (20%)
Clinical features: abnormal muscle fatiguability, muscle weakness
respiratory muscles may be severely affected (patients may need
mechanical ventilation)
Microscopic features: no light-microscopic abnormalities
Myositis (inflammation of muscles)
bacterial, viral (complication of systemic infections)
autoimmune myositis: dermatomyositis/polymyositis
Trichinosis
eating meat containing viable cysts of Trichinella spiralis (improperly cooked
pork products)
larvae released after ingestion, and penetrate into blood throught duodenal
mucosa → dissemination throughout the body (lung, heart, brain, skeletal
muscles)
larvae enclosed within the membrane (parasitic cysts), calcification of dead
cysts
Myositis ossificans
tumor-like lesion sometimes preceded by trauma
must be distinguished from extraskeletal osteosarcoma
central area of plump, mitotically active fibroblasts surrounded by zones of
immature woven bone and mature lamellar bone