3/11/99

Pathology II

 

Infectious Arthritis

·        Lyme Disease

·        Caused by spirochete Borrelia burgdorferi

·        Transmitted from rodents to people via deer ticks

·        The major arthropod-borne disease in US, also frequent in Europe and Japan

·        Clinical disease occurs in three stages:

1.      stage 1

·        skin lesion at site of tick bite—erythema chronicurn migrans

·        fever and lymphadenopathy

·        last few weeks

2.      stage 2 – Early disseminated stage

·        hematogenous spread of spirochetes

·        secondary annular skin lesions, lymphadenopathy, migratory joint and muscle pain, cardiac arrhythmias, meningitis w/cranial nerve involvement

·        last weeks to months

3.      stage 3 – late disseminated stage (chronic)

·        occurs 2-3 years after initial bite

·        chronic arthritis – severe damage to large joints – 80% of patients

·        most common are knee, shoulder and elbow

·        encephalitis that varies from mild to debilitating

·        fig from book; time line

Diseases of Musculoskeleton System

·        type 1

·        type 2

·        diseases

·        1.  Muscle atrophy

 

1.      Neurogenci Atrophy

·        Normal innervation is impaired—skeletal mm undergoes progressive atrophy

·        Microscopically, fiber appear angular and atrophic—tend to lie in clusters; small group atrophy—both type 1 and 2 are affected

·        ­ activities of oxidative enzymes—staining helps distinguish denervated atrophy form other mm atrophies

·        if nerve regeneration and re-establish contact, nerve s

·        clinical features

·        muscle weakness—mild localized to severe, generalized weakness w/respiratory compromise sprouts innervate contiguous fibers, producing fibers

·        infantile spinal muscular atrophy® "floppy infant syndrome"

 

Type II Myofiber Atrophy

·        very common abnormality of skeletal mm

·        disuse atrophy from immobilization or exogenous glucocorticoid use (Cushing's syndrome)

·        microscopic appearance is similar to denervation atrophy, but type I fibers are not affected.  This is primary point of Dx differentiation

·        clinical manifestation—muscle weakness

 

Myasthenia Gravis

·        acquired autoimmune disorder of neruomuscular transmission characterized by muscle weakness

·        females of any age; males in late adult life

·        antibodies against acetylcholine receptor (AchR) either injure receptor or inhibit it binding of acetylcholine

·        other associated autoimmune disorders:  SLE, RA, Sjogren's syndrome

·        thymic abnormalities are common:  2/3rds have thymic hyperplasia, 15%-20% have thymomas.  Thymectomy improves condition

·        muscle weakness—worse w/repeated contraction or stimulatino—esp later in the day

·        muscles of eyelid®ptosis (drooping)

·        eye movement®double vision

·        face and neck muscles®difficulities w/chewing and holding head up

·        speech has a nasal quality

·        respiratory mm involvement may result in respiratory failure, if untreated

 

Muscular Dystrophies

·        Duchenne

·        X-linked hereditary disease cuasd by absences of a

·        Large pro

·        Skeltal and cardiac mm dystrophin attaches to sacrocmer (I and M bands)—structural and fxnal

·        Becker

·        Another x-linked

·        Dystrophin is present, but abnormal

·        Muscle abnormalities are less severe than DMD

 

Morphology

·        Hitologic features (both types)—marked variation in muscle fiber size—concomitant hypertrophy and atophy

·        Comination of degenerative and regenration

·        Connective tissue is increased

·        Males are affected

·        Mm weakness, ititally in proximal mm

·        Early manifestation:  generalized clumsiness, w/ weakness in pelvic and shoulder girdles

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