Archive by category 'Surgpedia'
May 31st, 2010
Pathophysiology
infection with Epstein-Barr virus (or sometimes CMV with slightly different clinical presentation) in adolescence or early adulthood
Signs and Symptoms
1) prodrome of fatigue, malaise, and myalgias 2) tender but mobile lymphadenopathy (especially in posterior cervical chain) 3) fever 4) exudate pharyngitis 5) splenomegaly 6) splenic rupture (0.5%) 7) mouth petechiae 8) gingivitis 9) abdominal pain 10) rash (10%) 11) symptoms usually resolve in 3-4 weeks
Characteristic Test Findings
Laboratory – 1) leukocytosis with at least 10% lymphocytes 2) presence of Paul-Bunnell heterophile antibody (this is the basis of the diagnostic monospot test) 3) presence of transient cold agglutinins 4) increased AST, ALT, alkaline phosphatase
Histology/Gross Pathology
1) atypical lymphcytes (mostly CD8+ T-cells) with clumped chromatin and irregular nuclei surrounded by RBCs (ballerina-skirt) 2) atypical lymphocytes resemble Reed-Sternberg cells, causing diagnostic confusion 3) infiltration of splenic red pulp (and lymph node sinuses) with atypical lymphocytes 4) EBV is a linear, double-stranded DNA virus 5) CMV intranuclear with “halos”
Associated Conditions
1) splenic rupture (0.5%) 2) bacterial superinfection (10%) 3) autoimmune hemolytic anemia (2%) 4) rash if ampicillin is given (90% of cases not considered a true allergic reaction) 5) fulminant liver failure 6) CNS involvement (ataxia, hemiplegia, psychosis) 7) Guillain-Barre syndrome 8) pneumonia 9) arthritis
Biochemistry
1) virus binds to nasopharyngeal cells and B-lymphocytes, which carry it systemically 2) activated T-lymphocytes kill Ebstein-Barr infected B-lymphocytes
Inheritance/Epidemiology
1) prodrome lasts 4-6 weeks 2) asymptomatic carriers intermittently shed virus 3) person-to-person contact is via infected oral secretions
Treatment
supportive in immunocompetent individuals
Tips for USMLE
1) CMV mononucleosis differs from EBV mononucleosis – CMV etiology usually does not cause pharyngitis or posterior neck lymphadenopathy and does not have Paul-Bunnell heterophile antibodies 2) a heterophile antibody is a human antibody that reacts with the blood cells of another species, such as a sheep or guinea pig 3) if question mentions an 18 year old college freshman who develops a “dragged-out feeling” in the middle of the semester and then develops a headache, sore throat, and enlarged posterior neck lymph nodes during finals, think mononucleosis from EBV.
May 30th, 2010
Pathophysiology
1) group of seven different disorders 2) most common variant is caused by deficiency in cystathionine-beta-synthase 3) thought to involve abnormal cross-linking of collagen, fibrillin, and macromolecules
Signs and Symptoms
1) mental retardation/psychiatric problems 2) tall stature 3) skeletal defects (osteoporosis) 4) retinal detachment 5) increased thromboses 6) lens dislocation (downward and medially) 7) severe atherosclerosis
Characteristic Test Findings
Laboratory – 1) increased serum homocystine 2) increased urine homocytine 3) increased serum methionine in some variants 4) positive cyanide-nitroprusside test
Associated Conditions
1) myocardial infarction 2) pulmonary embolus 3) cerebral vascular accidents 4) deep venous thrombosis 5) peripheral artery disease 6) vision loss and glaucoma
Biochemistry
second most common variant has defect in methionine synthase
Treatment
1) early pyridoxine (induces cystathionine beta synthase activity) to blunt development of sequelae 2) low protein diet to methionine intake 3) maintenance of physiologic levels of cofactors folate, vitamin B6, and vitamin B12
Tips for USMLE
1) clinical features can be confused with Marfan’s disease 2) best way to differentiate is the mental retardation that occurs in homocystinuria but not Marfan’s 3) the lens subluxation in Marfan’s is upward and outward; in homocystinuria, it is downward and inward
May 24th, 2010
Pathophysiology
1) Rickettsial infection caused by Coxiella burnetii 2) acute and chronic forms exist
Signs and Symptoms
1) Severe headache 2) fever/chills/sweats 3) myalgias 4) extreme fatigue 5) dry cough 6) hepatosplenomegaly 7) nausea/vomiting 8) in immunocompetent hosts usually self-limited over 10-14 days 9) chronic form almost always involves endocarditis with a wide variety of other syndromes (see below)
Characteristic Test Findings
Radiology – 1) chest radiograph shows focal bronchopneumonia 2) CT scan shows “doughnut ring” pattern in liver parenchyma Laboratory – 3) positive rheumatoid factor 4) increased erythrocyte sed rate 5) increased C-reactive protein 6) increased gamma-globulin 7) thrombocytopenia initially followed by reactive thrombocytosis 8) diagnosis is by positive serology via indirect immunofluorescence
Histology/Gross Pathology
1) organism is small, pleomorphic, gram-negative coccobacillus 2) liver granulomata
Associated Conditions
chronic form has increased incidence of – 1) endocarditis 2) pericarditis 3) myocarditis 4) hepatitis 5) pancreatitis 6) deep vein thrombophlebitis 7) optic neuritis 8) Guillain-Barre syndrome 9) SIADH 10) orchitis 11) lymphadenopathy 12) erythema nodosum
Biochemistry
organism enters cells after being phagocytocized by macrophages
Inheritance/Epidemiology
1) infection is via inhalation, drinking infected milk, or contact with infected products of gestation (placenta) 2) vectors are goats, sheep, and cattle 3) most commonly found in butchers, veterinarians, and dairy workers 4) person-to-person contact is possible 5) initial presentation varies by geographical region – pneumonia in Canada and hepatitis in France
Treatment
1) acute disease – doxycycline for 2-3 weeks 2) chronic form – doxycycline and rifampin for 18-36 months
Tips for USMLE
1) unlike most rickettsial infections, there is usually no skin rash 2) WBC are usually normal 3) if sheep herder in France develops severe headache, fever, chills with enlarged tender liver, inflamed blood clots in his left calf, and a platelet count of 800,000/dL, think Q fever
May 23rd, 2010
Pathophysiology
1) type of lysosomal storage disease 2) cause is defect (multiple types possible) in alpha-galactosidase with altered metabolism of glycosphingolipid 3) onset is in childhood
Signs and Symptoms
1) angiokeratomas (telangiectasias of skin) that are blue-black to red and do not blanch – they increase in size and number as patient ages and are most dense on upper legs 2) acroparesthesias 3) small vessel disease of the brain, heart, and kidneys 4) hypohidrosis 5) abdominal pain that is worse with stress or fatigue 6) early coronary artery disease 7) lens and corneal opacities 8) leg lymphedema 9) episodic diarrhea 10) arthropathy of finger joints
Characteristic Test Findings
Laboratory – 1) hematuria 2) proteinuria
Histology/Gross Pathology
1) cellular accumulation of trihexosylceramide (THC), especially in endothelium 2) characteristic myeloid bodies seen on kidney biopsy
Associated Conditions
1) renal failure 2) leg lymphedena 3) hypertension 4) left ventricular hypertrophy 5) angina 6) congestive heart failure 7) stroke 8) focal segmental glomerulosclerosis 9) restrictive cardiomyopathy
Biochemistry
alpha-galactosidase A enzyme cleaves the terminal end of THC, which is a step in the metabolism of glycosphingolipid
Inheritance/Epidemiology
1) X-linked disorder (GLA gene on Xq22) 2) occurs in 1/40,000 3) most severe in men – heterozygous females have some symptoms but lack the severe organ involvement
Treatment
1) phenytoin and carbamazepine decrease the acroparesthesias 2) hemodialysis and kidney transplantation for renal failure 3) enzyme therapy
Tips for USMLE
angiokeratomas tend to be most numerous on thighs
May 22nd, 2010
Pathophysiology
1) glycogen storage disease with increased accumulation of glycogen in skeletal muscles 2) cause is defect in muscle phophorylase 3) not progressive and only slightly debilitating
Signs and Symptoms
1) onset of symptoms in late teens/early adulthood 2) muscle spasms, pain, fatigue, and cramps on exercise or exertion (worse if activity is brief and intense such as running up stairs) 3) if patient rests after exertion, a second wind effect takes place and symptoms lessen
Characteristic Test Findings
Laboratory – 1) lack of lactate production (used as a diagnostic test) 2) myoglobinuria 3) increased CK (may be 100 times normal) 4) increases serum ammonia 5) diagnosis is also made by histochemical reaction for myophosphorylase, gene studies of DNA, and biochemical assay of enzyme activity in muscle
Histology/Gross Pathology
1) myofiber necrosis is evident on strenuous exercise 2) slight accumulation of glycogen particles is visible in sarcoplasm
Associated Conditions
renal failure if severe myoglobinuria occurs and is not treated
Biochemistry
1) muscle phophorylase causes release of glucose-1-phosphate from glycogen 2) if muscle phophorylase is absent the 1.4 glycosidic chains cannot be cleaved
Inheritance/Epidemiology
1) autosomal recessive 2) cause is a nonsense gene mutation on chromosome 11q13, which causes arginine to be changed to a stop codon 3) more common in men
Treatment
1) symptoms do not occur if there is no muscle exercise 2) if myoglobinuria occurs, patient needs hydration and vigorous diuresis 3) exercise tolerance can be improved with graduated aerobic activity 4) controversy exists as to whether diet modification (high protein diet, glucose ingestion before exercise) lessens symptoms
Tips for USMLE
if a 17 year old male experiences for the first time stabbing pain in his legs and arms when he is carrying furniture into his third-floor dorm room and then notices wine-colored urine, think McArdle’s
May 22nd, 2010
Pathophysiology
1) caused by an infection with Mycobacterium leprae 2) clinical disease occurs in peripheral nervous system, skin, eyes, testes, and upper respiratory tract 3) four different forms occur along a continuum of mild and self-limiting disease to severe and disfiguring disease; they are least to most severe – polar tuberculoid, borderline tuberculoid, borderline lepromatous, and polar lepromatous 4) the lepramatous forms can have an additional superimposed disease exacerbation – lepra type 1 reaction and lepra type 2 reaction 5) lepra states are immunologically mediated inflammatory states 6) an additional disease condition called Lucio’s phenomenon occurs only in Mexico and the Caribbean
Signs and Symptoms
Tuberculoid forms – 1) initial lesion is nonpruritic, hypopigmented, hyperesthesic, and sharply demarcated papule that enlarges peripherally 2) edges elevate as lesion expands, with center becoming atrophic and anesthetic – also with dry, scaly skin and loss of sweat glands and hair follicles Lepromatous forms- 3) skin-colored papules and nodules up to 2 cm in diameter that eventually coalesce 4) leonine facies 5) loss of eyebrows and eyelashes (in lateral areas initially) 8) ulceration of skin over plantar heads 9) foot drop 10) destruction of nasal cartilages with saddle nose deformity 11) blindness (cataracts, uveitis) 12) impotence and infertility 13) amyloidosis
Characteristic Test Findings
Laboratory – 1) false-positive ANA, VDRL, RA Erythema nodosum leprosum – 2) increased alpha-TNF 3) anemia 4) leukocytosis 5) increased transaminases
Histology/Gross Pathology
1) obligate intracellular bacillus with complex cell wall – stains acid fast and best visualized in tissue with modified Fite stain 2) destruction of dermal nerves by T cells (pathognomonic for leprosy) 3) enlargement of peripheral nerves – especially peroneal and ulnar 4) noncaseating granulomas with Langhans’ giant cells and lymphocytes (tuberculoid forms) 5) large clumps of bacilli in dermis (lepromatous forms) 6) foam cells in dermis 7) axonal and Wallerian degeneration
Associated Conditions
Lucio phenomenon – large, ulcerative lesions on legs that become secondarily infected with bacteria
Inheritance/Epidemiology
1) occurs almost entirely in third world countries (India, Brazil, Nigeria, Myanmar, Indonesia, Caribbean) 2) in USA – 200 cases/year; almost entirely in immigrants from those areas, except in Texas where armadillo contact can transmit the organism 3) incubation period is 5-25 years.
Treatment
1) polar tuberculoid form can be self-limited and heal spontaneously 2) lepra type 1 state – glucocorticoids for 3 months 3) lepra type 2 – antipyretics, steroids for 1-2 weeks, and thalidomide if two courses of steroids has failed 4) rapid surgical decompression of nerve abscesses 5) dapsone is main drug used in combination with rifampin and clofazimine.
Tips for USMLE
1) if question mentions destruction of dermal nerves or neurons by T cells, it is leprosy 2) if question mentions enlarged peripheral nerves, think leprosy 3) if question mentions globi, think leprosy 4) leprosy is chiefly a disease of the dermis
April 27th, 2010
Pathophysiology
1) necrotizing vasculitis of early childhood 2) generalized rash (exantham) 3) fever 4) conjuncitivitis 5) lymphadenitis 6) oral lesions 7) possible infectious cause includes parvovirus B19
Signs and Symptoms
1) fever (always present) 2) skin rash 3) conjuncitivitis 4) lymphadenopathy 5) coronary artery aneurysms (25%) 6) cervical adenitis 7) strawberry tongue (also seen in scarlet fever) 8) crusting and fissuring of lips 9) erythema of hands and feet followed by desquamation 10) edema of mucous membranes
Characteristic Test Findings
Laboratory – 1) antiendothelial cell antibodies 2) increased IL-2 receptors 3) increased IL-1 receptors
Histology/Gross Pathology
1) infarcts and hemorrhage in heart and kidney 2) vasculitis of medium-size arteries
Associated Conditions
1) pericarditis 2) myocarditis 3) myocardial infarction 4) cardiomegaly 5) Staphylococcus aureus 6) toxic shock syndrome
Biochemistry
1) overstimulation of immune system is postulated 2) possibly caused by microbial stimulated production of superantigen to major histocompatiblity class 2 receptors and V-beta region of T cell receptor
Inheritance/Epidemiology
mortality is 3%
Treatment
1) generally unresponsive to antibiotics 2) aspirin 3) high dose gamma globulin
Tips for USMLE
1) clinically resembles scarlet fever and toxic shock syndrome 2) diagnosis – presence of fever ofr > 5 days and presence of four of the following: bilateral conjunctivitis, exanthem
April 13th, 2010
Pathophysiology
1) focal area of cystic, spongiform expansion of spinal cord (syrinx) 2) often produces a progressive myelopathy 3) most typical in high cervical and cervical/thoracic cord areas (although can occur anywhere in cord and also in medulla and pons) 4) syrinx is usually filled with collection of CSF 5) some cases result from blocked outflow of CSF from fourth ventricle through foramina of Luschka and Magendie to subarachnoid space (also occurs in absence of obstruction)
Signs and Symptoms
Typical – 1) “central cord syndrome” with pain and sensory loss in upper extremities 2) sensory loss to patient feels like a cape has been placed on back of neck, shoulders, and arms 3) arreflexia in upper extremities 4) weakness in upper extremities 5) muscle loss in same distribution as sensory loss 6) bladder/bowel dysfunction 7) spasticity and weakness in legs 8) Horner’s syndrome If associated with Arnold-Chiari malformation 9) cough 10) headache If affects medulla and pons - 11) vocal cord paralysis 12) dysarthria 13) nystagmus 14) recurrent dizziness 15) tongue weakness If affects descending tract of trigeminal nerve - 16) facial numbness and sensory loss
April 12th, 2010
Pathophysiology
1) pneumoconiosis owing to chronic inhalation of crystalline silicon dioxide 2) can result in pulmonary fibrosis from chronic injury to lung tissue
Signs and Symptoms
1) nonproductive cough 2) in advanced disease with pulmonary fibrosis, dyspnea and tachypnea occur
Characteristic Test Findings
Radiology – 1) chest radiograph shows “eggshell” calcifications in hilar lymph nodes and honeycomb lung PFTs – 2) both restrictive and obstructive impairment occurs
Histology/Gross Pathology
1) macrophages phagocytose silica particles 2) results in nodule formation in lung parenchyma (areas of fibrosis entrapping silica particles) 3) especially affects upper lung lobes
Associated Conditions
1) increased incidence of tuberculosis 2) Caplan’s syndrome (fibrosis and rheumatoid disease)
Biochemistry
macrophages are killed when they engulf silica, with the resultant destruction of phagolysosomes and release of free radicals, proteases, and Il-1
Inheritance/Epidemiology
occurs in sandblasters, miners, and people who work in quarries
Treatment
removal from offending environment
Tips for USMLE
1) no increased risk of cancer 2) fibrosis may be progressive even though exposure stops
April 12th, 2010
Pathophysiology
1) inflammation of large arteries (especially aorta and branches) 2) type 1 – involvement of the aortic arch and branches 3) type 2 – involvement of descending thoracic and abdominal aorta and branches 4) type 3 – involvement of both arch and descending aorta and branches 5) other vessels commonly involved – retinal, CNS, and pulmonary arteries
Signs and Symptoms
1) dizziness/syncope 2) visual problems 3) dyspnea 4) intermittent claudication 5) loss of pulses 6) hypertension 7) arterial bruits 8) fever/night sweats 9) weight loss 10) malaise 11) arthralgias 12) anorexia 13) pain over involved vessels
Characteristic Test Findings
Laboratory – 1) increased serum renin (owing to renal artery stenosis) 2) mild anemia 3) increased sed rate 4) increased serum immunoglobulin levels Radiology - 5) stenosis and occlusion of affected arteries and aneurysms in aortic arch and distal aorta on arteriogram
Histology/Gross Pathology
1) thickened, focal, raised, plaques in arteries 2) panarteritis of walls with mononuclear cells, neutrophils, and Langerhans’ cells 3) intimal hyperplasia
Associated Conditions
1) stroke 2) relapsing polychondritis
Inheritance/Epidemiology
1) 90% of patients are women 2) onset usually before age 30 years 3) most patients are Asian 4) highly variable course with fulminant disease to spontaneous remissions
Treatment
1) early in course – corticosteroids or immunosuppression drugs (especially methotrexate) 2) late treatment – requires surgical bypass or atherectomy
Tips for USMLE
1) almost always affects the subclavian arteries 2) if a 23 year old Japanese woman develops pain over her right carotid artery, a blood pressure of 140/60 in her left arm and 80/40 in her right arm and no detectable pulse at her right radial artery, think Takayasu’s
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