Musculoskeletal, Skin, and Connective Tissue - Skeletal Muscle, NMJ, Soft Tissue tumors

tonystep1's version from 2013-05-12 19:49


Question Answer
Dermatomyositis PathologyInflammatory disorder of the skin and skeletal muscle - unknown etiology, some cases are associated with carcinoma (e.g. gastric carcinoma)
Dermatomyotistis Clinical FeaturesBilateral proximal muscle weakness ; distal involvement can develop late in disease. Rash of the upper eyelids (heliotrope); malar rash may also be seen. Red papules on the elbows, knucles, and knees (Grotton lesion)
Dermatomyositis Lab FindingsIncreased creatine kinase, positive ANA and anti-Jo-1 antibody. Perimysial inflammation (CD4-T cells) with peri-fasicular atrophy on biopsy.
Dermatomyositis treatmentCorticosteroids
Polymyositis Clincal featuresInflammatory disorder of skeletal muscle - resembles dermatomyositis clinically, but skin is not involved; endomysial inflammation (CD4-T cells) with necrotic muscle fibers is seen on biopsy
X-Linked Muscular Dystrophy PathologyDegenerative disorder characterized by muscle wasting and replacement of skeletal muscle by adipose tissue - Due to mutations of dystrophin - a. Dystrophin is important for anchoring the muscle cytoskeleton to the extracellular matrix b. Mutations are often spontaenous ; large gene size predisposes to high rate of mutation
Duchenne muscular dystrophy PathologyDue to deletion of dystrophin - presents as proximal muscle weakness at 1 year of age; progresses to involve distal muscles - a. Calf-pseudohypertrophy is characterisitic finding b. Serum creatine kinase is elevated - 2. Death results from cardiac or respiratory failure ; myocardium is commonly involved.
Becker muscular dystrophyDue to mutated dysrophin ; clinically results in milder disease
Systemic lupus erythematousus Clinical PresentationFever, fatigue, weight loss, Libman-Sacks endocarditis, hilar adenopathy, and Raynaud's phenomenon - Nephritis is common cause of death in SLE. Diffuse proliferative glomerulonephritis (if nephritic) ; membranous glomerulonephritis (if nephrotic)---------I'M DAMN SHARP - Immunoglobulins , Malar rash, Discoid rash, Antinuclear antibody , Mucositis (oropharyngeal ulcers) , Neurologic disorders, Serositis (pleuritis, pericarditis), Hematologic disorders , Arthritis, Renal disorders, Photosensitivity
Systemic lupus erythematosus Lab findingsa. Antinuclear antibodies (ANA) - sensitive, (primary screening) but not specific for SLE b. Antibodies to double-stranded DNA (anti-dsDNA) - very specific , poor prognosis c. Anti-smith antibodies (Anti-sm) - very specific, but not prognostic d. Antihistone antibodies - more sensitive for drug-induced lupus
Sarcoidosis PathologyCharacterized by immune mediated widespread noncaseating granulomas and elevated serum ACE levels.
Sacoidosis Clinical PresentationCommon in black females often asymptomatic except for enlarged lymp node. Incidental findings on CXR of bilateral hilar adenopathy or reticular opacities. Associated wtih restrictive lung disease (interstial fibrosis) , erythema nodosum, Bell's palsy, epithelial granulomas containing microscopic Schaumann and asteroid bodies, uveitis, and hypercalcemia (due to elevated 1alpha-hydroylase- mediated vitamin D activation in epitheliod macrophages)
Polymalgia rheumatica Clinical PresentationPain and stiffness in shoulder and hips, often with fever malaise, and weight loss. Does not cause muscular weakness. More common in women >50 years of age; associated with temporal giant cell arteritis.
Polymalgia rheumatic Lab findingsElevated EST and normal CK

NMJ Pathology

Question Answer
Myasthenia gravis pathologyAuto-antibodies against the postsynaptic acetylcholine receptor at the neuromuscular junction (most commonly seen in women)
Mysathenia gravis Clinical Featuresa. Muscle weakness that worsens with use and improves with rest ; classically involves the eyes, leading to ptosis and diplopia b. Symptoms improve with anticholinestase agents c. Associated with thymic hyperplasia or thymomal thymectomy improves symptoms
Lambert-Eaton Syndrome PathologyAntibodies against presynaptic calcium channels of the neuromuscular junction - arises as a paraneoplastic syndrome, most commonly due to small cell carcinoma of the lung. Impaired acetylcholine release - firing of presynaptic calcium channels is required for acetylcholine release.
Lambert-Eaton Syndrome Clinical Featuresa. Muscle weaknes that improces with use, eyes are usually spared b. Anticholinesterase agents do not improve symptoms c. Resolves with resection of the cancer

Soft Tissue Tumors

Question Answer
LipomaBenign tumor of adipose tissue - most common benign soft tissue tumor in adults
LiposarcomaMalignant tumor of adipose tissue - most common malignant soft tissue tumor in adults - Lipoblast is the characteristic cell
RhabdomyomaBenign tumor of skeletal muscle - Cardiac rhabdomyoma is associated with tuberous sclerosis
RhabomyosarcomaMalignant tumor of skeletal muscle - most common malignant soft tissue tumor in children - Rhadbomyoblast is the characteristic cell ; desmin positive ---Most common site is the head and neck ; vagina is the classic site in young girls.

Labs for autoimmune pathologies

Question Answer
Anti-dsDNAAnti-dsDNA are specific for SLE. Patients with SLE commonly have a malar "butterfly" facial rash that worsens with sun exposure. Patients also complain of low grade fever, joint swelling and/or tenderness, and oral ulcers
Anti-Centromere CREST syndrome - Calcinosis, Raynuad's phenonmenon, Esophageal dismotility, Sclerodactylyl and Telangiectasias.
Anti - DNA topoisomerase I (Scl-70)Are highly specific for systemic sclerosis (diffuse scleroderma)
Anti- HistoneAre found in drug-induced lupus - Procainamide, hydralazine, isoniazid, and D-Penicllamine are common causes of drug induced lupus - symptoms resemble SLE but without renal or CNS involvement
Anti - Ro/SSA and Anti - La/SSBSjorgen Syndrome - this condition is characterized by keratoconjunctivitis sicca (dry eyes) and xerostomia (dry mouth) - There maybe parotid enlargement, increased risk of other autoimmune diseases, and increased risk of non-Hodgkin lymphomas
Anti-phospholipidIn patients with SLE, and in anti-phospholipid antibody syndrome. Antiphospholipid antibody syndrome causes a hypercoagulable state and patients may suffer from miscarriages. Partial thromboplastin time (PTT) is paradoxically increased in these patients despite propensity toward thrombosis.