Skeletal Muscle and Peripheral Nerve Pathology Flashcards
Characteristics of polymyositis
Autoimmune disease seen in adults
It presents with bilateral proximal muscle weakness.
Microscopic exam demonstrates endomysial lymphocytic inflammation (mostly cytotoxic T8) and skeletal muscle fiber degeneration and regeneration
Characteristics of dermatomyositis
Connective tissue disorder involving inflammation of skeletal muscle and skin.
It can affect both children and adults.
It presents with bilateral proximal muscle weakness, skin rash of the upper eyelids and periorbital edema
Microscopic exam shows perimysial and vascular lymphocytic inflammation, perifascular fiber atrophy, and skeletal muscle fiber degeneration and regeneration
Characteristics of inclusion body myositis
Affects adults age>50
Causes slowly preogressive, asymmetrical distal muscle weakness.
Light microscopic shows autophagic vaculoes and inclusion bodies in addition to inflammation and necrosis
Characteristics of myasthenia gravis
Autoimmune disease characterized by autoiantibodies against the acetylcholine (ACh) receptor of the neuromuscular junction,resulting in muscular weakness predominantely affecting the facial muscles.
Females are affected more than males
Extraocular muscle weakness may lead to ptosis and diplopia; the weakness worsens with repeated contractions
Respiratory muscle involvement may lead to death
What is mysathenia gravis associated with?
Thymic hyperplasia
Thymomas
Characteristics of Lambert-Eaton syndrome
Frequently arises before a diagnosis of cancer is made, often in cases of small cell lung cancer
Patients report dry mouth and proximal muscle weakness.
Autoantibodies are directed against presynaptic calcium channels of the neuromuscular junction
Characteristics of Duchenne muscular dsytrophy
It is the most common and severe form of muscular dystrophy.
Affected boys are normal at birth but have onset of symptoms by age 5.
Clinical features:
Progressive muscular weakness
Calf pseudohypertrophy
Proximal weakness of shoulder and pelvic girdles
Possible heart failure and arrhythmias
Respiratory insufficiency and pulmonary infections as a result of decreased mucociliary clearance
What is the genetic inheritance of Duchenne muscular dystrophy?
Recessive X-linked form of muscular dystrophy leading to rapid progression of muscle degeneration.
The affected gene is the dystrophin gene on the X chromosome.
Mutation results in a virtual absence of the dystrophin protein
Characteristics of Becker muscular dystrophy
Recessive X-linked inherited disorder leading to slowly progressive muscle weakness of the legs and pelvis
Less severe than Duchenne
Not as common as Duchenne
Has a later onset than Duchenne, with variable progression
Mutation produces an altered dystrophin protein
Cardiac involvement is rare and patients can have relatively normal lifespan
Characteristics of lipoma
Benign adipose tissue tumor that most often arises in subcutaneous tissue of trunk, neck or proximal extremities.
It is the most common benign soft tissue tumor
Microscopically it is composed of mature fat cells but can contain other mesenchymal elements
Characteristics of liposarcoma
Malignant adipose tissue tumor that most often arises in the thigh or retroperitoneum
It is the most commonadult sarcoma.
It is distinguised from lipoma by the presence of lipoblasts
Grossly it tends to be larger than lipoma and the cut surface shows fibrous bands
Microscopically well-differentiated liposarcoma consists of mature fat with varying numbers of hyperchromatic spindle cells and multivacuolated lipoblasts
Characteristics of dermatofibroma
Benign dermal spindle cell proliferation that most often arises in the extremities
A small, red nodule is seen, which is tender and mobile on examination
Characteristics of fibromatosis
Non-neoplastic proliferative connective tissue disorder that can histologically resemble a sarcoma
Fibrous tissue infiltrates muscle or other tissue and may cause a mass lesion. The cut surface is trabeculated
Microscopically bundles of fibroblasts and collagen are seen
Characteristics of superficial fibromatoses
Arise from fascia or aponeuroses
Palmar fibromastosis is the most common type.
Characteristics of deep fibromatoses
Occur in extraabdominal sites (children) and abdominal wall and extraabdominal sites (adults)
Abdominal desmoids often occur in women within a year of pregnancy.
They may also follow surgery or trauma
Characteristics of fibrosarcoma
Malignant fibrous tumor, commonly seen on the thigh and upper limb.
It may arise spontaneously or after therapeutic/accidental irradiation.
Microscopically there are uniform spindle cells with a “herringbone” pattern.
Metastases are hematogenous, often to the lung
Characteristics of undifferentiated pleomorphic sarcoma
Previously known as malignant fibrous histiocytoma
Large multilobulated tumor seen in the extremities and retroperitoneum of older adults
Microscopically they may have a storiform (cartwheel-like) pattern.
They recur and metastasize
Characteristics of rhabdomyoma
Sarcoma botryoides
Affects infants and young children (age<5), in hwom it can cause a polypoid, “grapelike”, soft tissue mass that protrudes from the vagina
Characteristics of embryonal rhabdomyosarcoma
Benign skeletal muscle tumor that can involve the vagina.
It occurs in middle-aged women
Characteristics of leiomyoma
Benign smooth muscle tumor most often seen in the uterus and GI tract.
Less often it is seen in skin, and only rarely in deep soft tissue
Characteristics of leiomyosarcoma
Soft tissue is less common than its counterpart in the GI tract and uterus.
In soft tissue is usually arises in the retroperitoneum of older women
Grossly the tumor is fleshy and white with hemorrhage and necrosis.
Microscopically the the tumor nuclei are blunt ended (“cigar shaped”). Longitudinal striations can be seen with Masson trichrome staining. The tumor is highly aggressive in the retroperitoneum
Characteristics of botulism
Caused by exposure to a neurotoxin produced by Clostridium botulinum
Mechanism of action of the neurotoxin- blocks the release of acetylcholine from presynaptic neurons
Characteristics of toxic myopathy
Caused by corticosteroid use ICU Chloroquine and hydroxychloroquine Alcohol Hypothyroidism
Characteristics of myotonic dystrophy
AD multisystem disorder
Expanisions of CTG triplet repeats in the 3’-noncoding region of the myotonic dystrophy protein kinase (DMPK) gene on chromosome 19
Selective atrophy of type I fibers
Clinical features: Muscle weakness and wasting Myotonia (prolonged muscle contractions) Cataracts Frontal balding Testicular atrophy Arrhythmias
Characteristics of malignant hyperthemia
Mutations in the RYR1 gene
Disrupt the function of the ryanodine receptor
Clinical features: Tachycardia Tachypnea Muscle spasms Hyperpyrexia Rhabdomyolysis
Characteristics of fibromyalgia
Syndrome characterized by widespread MSK pain without evidence of muscle inflammation or increase in muscle enzymes
Clinical features:
Fatigue and sleep disruption (easily fatigued, unrefreshed sleep)
Psychiatric (anxiety, depression)
Somatic symptoms (headache)
Cognitive disturbance (learning, memory, perception and problem solving)
Muliple, symmetric tender spots over joints, muscle, tendons
Characteristics of polymyalgia rheumatica
Muscle pain and stiffness in the neck, shoulder, and pelvic girdle
Worse in the mroning and with activity
Known association with giant cell (temporal) arteritis
Characteristics of psoas abscess
Causes:
Fever, back/flank pain, inguinal mass, difficulty walking
Pain referred to hip or knee
Pain exacerbated by movements that cause the psoas to be stretched to extended, such as hip extension
