Property:Explanation
Jump to navigation
Jump to search
This is a property of type Text.
W
Leukocoria refers to an abnormal white reflection from the retina where a usual red reflex is expected. Leukocoria in infants raises concern for two important entities: congenital cataracts and retinoblastoma. Retinoblastoma is a rapidly progressing tumor that develops from cells of a retina. It can either be sporadic or inherited. In both cases, the tumor develops due to a mutation in the RB1 gene whose protein product, the retinoblastoma protein, is a tumor suppressor that inhibits G1-to-S transition and regulates the cell cycle. In its inherited form, the mutation of the RB1 gene predisposes to other malignancies later in life.<br/>
'''Educational Objective:''' Leukocoria is an abnormal white reflex that can be seen in children with retinoblastoma. Retinoblastoma occurs due to a mutation in the RB1 gene.<br/>
'''References:''' Abramson DH, Frank CM, Susman M, Whalen MP, Dunkel IJ, Boyd NW. Presenting signs of retinoblastoma. J Pediatr. 1998;132(3 Pt 1):505-8. +
Infectious mononucleosis is a clinical syndrome characterized by fever, pharyngitis, and lymphadenopathy usually caused by Ebstein-Barr virus (EBV) although several other infectious etiologies can give a mononucleosis-like syndrome including toxoplasma, and cytomegalovirus (CMV). The diagnosis is usually clinical supported by serologies and by peripheral smear showing atypical lymphocytes. Another test used to detect EBV mononucleosis vs. other mononucleosis-like syndromes is the heterophile antibody test. The test checks for agglutination of horse (Monospot test) or sheep (Paul-Bunnell test) red blood cells when mixed with the patient's serum containing the heterophile antibodies produced by EBV infected plasma cells. EBV binds to CD21 on the surface of B-cells allowing them to fuse and enter. EBV mononucleosis can be easily mistaken for streptococcal pharyngitis, and streptococcal testing is often indicated.<br/>
'''Educational Objective:''' EBV causes mononucleosis by binding CD21 on the surface of B-cells. EBV infectious mononucleosis can be detected via heterophile antibody testing.<br/>
'''References:''' Luzuriaga K, Sullivan JL. Infectious mononucleosis. N Engl J Med. 2010;362(21):1993-2000. +
''Trichomonas vaginalis'' is an anaerobic protozoan and the the causative agent of trichomoniasis, one of the most common sexually transmitted infections. As the organism only has trophozoites and no cysts, transmission occurs directly. ''Trichomonas'' usually infects the urogenital tract causing vaginitis in women and urethritis in men. A frothy thick green vaginal discharge can be observed and is typically very malodorous. Diagnosis is usually by detecting motile trophozoites on vaginal wet-mount. Treatment is with metronidazole for both partners to prevent reinfection.<br/>
'''Educational Objective:''' Patients with ''Trichomonas vaginalis'' vaginal infection typically present with malodorous greenish vaginal discharge associated with vaginal itching and burning. Diagnosis of trichomoniasis is usually by detection of motile trophozoites on vaginal swab.<br/>
'''References:''' Schwebke JR, Burgess D. Trichomoniasis. Clin Microbiol Rev. 2004;17(4):794-803. +
I-cell disease is a rare autosomal recessive lysosomal storage disorder that manifests very early in life. Clinically, it is characterized by failure to thrive, coarse facial features, corneal clouding, and limitations in joint movement with hip dislocation. The pathophysiology of I-cell disease is related to a defect in mannose-6-phosphate tagging of enzymes that are to be transported into lysosomes. Instead, lysosomal enzymes are secreted outside the cell, leading to an increase in their plasma concentrations. Treatment is usually supportive. Bone marrow transplant may be effective in some patients.<br/>
'''Educational Objective:''' I-cell disease is characterized by a defect in mannose-6-phosphate tagging of lysosomal enzymes.<br/>
'''References:''' Güngör N, Coşkun T, Akçören Z, Cağlar M. I-cell disease. A case report and review of the literature. Turk J Pediatr. 1994;36(2):145-52.<br>
First Aid 2015 page 73. +
Buspirone is an anxiolytic drug used mainly in the treatment of generalized anxiety disorder. Compared to other treatments, it was shown to be effective in mild to moderate GAD however, it is particular in that it is nonsedative even causing insomnia in some patients. Buspirone also has very low risk of addiction of tolerance. The mechanism of action of buspirone is poorly understood. It acts as serotonin 5-HT<sub>1A</sub> receptor agonist but also possesses α1 receptor agonist and dopamine antagonist properties. A common mneumonic used to remember the characteristics of buspirone is "I SAT on the BUS". SAT stands for NO sedation, addiction, or tolerance.<br/>
'''Educational Objective:''' Buspirone alleviates anxiety without causing sedation, addiction or tolerance.<br/>
'''References:''' Eison AS, Temple DL. Buspirone: review of its pharmacology and current perspectives on its mechanism of action. The American Journal of Medicine. 1986;80(3):1-9. +
Oral contraception is a common and relatively safe means of contraception that usally combines both estrogen and progestin in different doses. OCPs work by inhibiting the positive estrogen feedback loop that leads to the LH surge and eventual ovulation. OCPs have been shown to be safe and are not associated with an increased risk of cancer or thromboembolism in the general population. OCPs are usually contraindicated in certain sub-populations at higher risk of adverse events including patients with the following characteristics:
* Smokers >35 years of age
* Previous personal history of DVT, PE, or stroke
* Previous personal history of estrogen dependent breast cancer<br/>
'''Educational Objective:''' OCPs are contraindicated in female smokers >35 years of age due to the increased risk of cardiovascular events.<br/>
'''References:''' Marchbanks PA, Mcdonald JA, Wilson HG, et al. Oral contraceptives and the risk of breast cancer. N Engl J Med. 2002;346(26):2025-32.<br>
Pomp ER, Rosendaal FR, Doggen CJ. Smoking increases the risk of venous thrombosis and acts synergistically with oral contraceptive use. Am J Hematol. 2008;83(2):97-102.<br>
Shapiro S, Rosenberg L, Slone D, Kaufman D, Stolley P, Miettinen O. Oral contraceptive use in relation to myocardial infarction. The Lancet. 1979;313(8119):743-747.<br> +
Foscarnet is an antiviral pyrophosphate analog that is predominantly used in patients with moderate to severe herpes virus and CMV infections. The patient is this scenario is presenting with decreasing visual acquity in the context of a very low CD4 count raising the suspicion for CMV retinitis. Foscarnet acts by binding proximally to the pyrophosphate-binding site on the viral DNA polymerase, blocking the exchange of pyrophosphate from deoxynucleotide triphosphates and leading to DNA chain termination. Forscarnet does not require any ''in vivo'' modification to be functional compared to other antivirals like acyclovir and ganciclovir. A rare but serious complication of foscarnet administration is electrolyte imbalance particularly hypomagnesemia, hypocalcemia, and hypophosphatemia. It is common to observe a decrease in PTH levels as well.
This patient has the typical presentation CMV retinitis which he is at high risk for given his CD4 count. Any patient with a CD4<50 and visual disturbances should be worked-up for CMV retinitis.<br/>
'''Educational Objective:''' A rare complication of foscarnet is electrolyte imbalance, typically hypomagnesemia, hypocalcemia, and hypophosphatemia.<br/>
'''References:''' Buckley MS, Leblanc JM, Cawley MJ. Electrolyte disturbances associated with commonly prescribed medications in the intensive care unit. Crit Care Med. 2010;38(6 Suppl):S253-64. +
Torsades de pointes is a ventricular tachycardia characterized by polymorphic wave forms with typical crescendo-decrescendo pattern about the isoelectric line. Torsades de pointes is a complication of prolonged QT interval that can progress to ventricular fibrillation and sudden death. Many medications can lead to torsades de pointes, but the classical drugs associated with QT prolongation include Class IA and Class III antiarrhythmics (except amiodarone). Dofetilide is a class III antiarrhythmic used in the treatment of atrial fibrillation for the restoration of regular rhythm. It is a complication that can be seen in up to 10% of patients in certain studies often indicating the need for hospitalization and close monitoring of patients receiving this agent.<br/>
'''Educational Objective:''' Torsades de pointes is a complication of medications that increase the QT interval such as Class IA and Class III antiarrhythmics namely dofetilide.<br/>
'''References:''' Viskin S. Long QT syndromes and torsade de pointes. The Lancet. 1999;354(9190):1625-1633. +
The patient's symptoms and signs are classical findings of pancreatic cancer. One of the most lethal human cancers, it is often detected late in the course of disease due to its silent nature. Important risk factors include smoking, male gender, family history, chronic pancreatitis, and ethnicity (African-Americans). The most important pathways involved in the tumorigenenis of pancreatic adenocarcinoma include products of the KRAS, RB1, and TP53 genes. A tri-phasic pancreatic-protocol CT is the initial diagnostic test of choice for patients with suspected pancreatic cancer. An important complication observed in pancreatic cancer patients is Trousseau syndrome or migratory thrombophlebitis. Trousseau syndrome is defined as either spontaneous recurrence of migratory venous thromboses, or arterial emboli by non-bacterial endocarditis in patients with cancer.<br/>
'''Educational Objective:''' Pancreatic cancer is considered a hypercoagulable state associated with migratory thrombophlebitis or Trousseau syndrome.<br/>
'''References:''' Vincent A, Herman J, Schulick R, Hruban RH, Goggins M. Pancreatic cancer. Lancet. 2011;378(9791):607-20.<br>
Callander N, Rapaport SI. Trousseau's syndrome. West J Med. 1993;158(4):364-71. +
The patient's caloric intake must be calculated based on knowledge of the following:
1 gram of protein = 4 kcal <br> 1 gram of carbohydrates = 4 kcal <br> 1 gram of fat = 9 kcal
Accordingly, the following equation may be calculated: (250x4) + (700x4) + (200x9) = (1000 + 2800 + 1800) = 5600 kcal.<br/>
'''Educational Objective:''' 1 gram of protein = 4 kcal <br> 1 gram of carbohydrates = 4 kcal <br> 1 gram of fat = 9 kcal<br/>
'''References:''' +
The brain generally uses up to 70% of total body glucose requirements, and always requires a steady supply of energy producing substances for normal functioning. The experiment shows that upon starvation, brain cells decrease their consumption of glucose and and increase their consumption of ketone bodies instead. There are 2 main ketone bodies produced in states of starvation: Beta-hydroxybutyrate and acetoacetate. Acetoacetate levels rise following starvation, but they never reach concentrations as high as beta-hydroxybutyrate. An overnight fast in physiologic conditions, is not enough to drive the body to switch to ketotic metabolism. In the first 12-18 hours, glycogen stores kick in to maintain glucose levels at baseline. However, following prolonged starvation, glucose only represents less than 1/3 of the energy source of the brain. The brain's capacity to extract ketone bodies, as well as overall ketone body blood concentrations rise; these bodies become the main supply of nutrition to brain cells in such moments of stress. Although fatty acids can be utilized everywhere else in the body, they are not used by the brain because they do not cross the blood brain barrier.<br/>
'''Educational Objective:''' Beta-hydroxybutyrate and acetoacetate are ketone bodies that are consumed by the brain in prolonged starvation.<br/>
'''References:''' Cahill GF, Veech RL. Ketoacids? Good medicine?. Trans Am Clin Climatol Assoc. 2003;114:149-61. +
Squamous cell carcinoma is a common cancer that affects approximately 100 to 150 per 100,000 persons annually in the United States. Squamous cell carcinoma should be highly suspected in any patient who presents with an ulcerating, non-healing lesion located in a sun-exposed region (such as the face, head, or neck region). Furthermore, physical examination findings, namely the dark-red color, asymmetry, and location at the lower lip, should raise the suspicion of squamous cell carcinoma in this patient. The diagnosis of squamous cell carcinoma requires biopsy, which typically demonstrates concentric epithelialized cells with foci of central keratinization (keratin pearls). The most important risk factor for the development of squamous cell carcinoma of the skin is chronic ultraviolet radiation, often observed among patients with long-standing history of sun exposure and sunburns. Arsenic, which was used in drug manufacturing in the past, is also associated with carcinogenesis and development of squamous cell carcinoma of the skin. Other important risk factors include history of ulcerating or chronic skin lesions (e.g. chronic draining sinuses or osteomyelitis) and precancerous lesions (such as actinic keratosis, bowenoid papulosis, and epidermodysplasia verruciformis). Immunosuppression (transplant, hematologic malignancies, drug-induced), HPV infection (6 and 11), and chronic exposure to ionizing radiation, metal-ore, insecticides, and aromatic hydrocarbons are also predisposing condition. Finally, genetic factors, such as xeroderma pigmentosa or albinisim, are usually associated with the development of early-onset squamous carcinoma of the skin.<br/>
'''Educational Objective:''' Squamous cell carcinoma should be highly suspected in any patient who presents with an ulcerating, non-healing lesion at a sun-exposed region. On biopsy, the lesion typically demonstrates concentric epithelialized cells with foci of central keratinization (keratin pearls).Chronic exposure to arsenic has been associated with the development of squamous cell carcinoma of the skin.<br/>
'''References:''' Alam M, Ratner D. Cutaneous squamous-cell carcinoma. N Engl J Med. 2001;344:975-83.<br>
First Aid 2014 page 438
Pancreatic divisum is considered the most common variant of pancreatic ductal configuration that occurs in approximately 10% of the population. It is caused by failure of fusion of the dorsal and the ventral pancreatic ducts. Most patients with pancreatic divisum are asymptomatic and the diagnosis is based on incidental findings during ERCP. Only the minority of patients with pancreatic divisum are symptomatic and generally complain of non-specific recurrent abdominal pain and episodes of pancreatitis. Although no definitive cause for the symptoms has been confirmed, it is believed that the partial obstruction of pancreatic fluid at the level of the minor papilla causes an elevated pressure within the ducts and leads to pancreatitis. Symptomatic treatment for such patients is endoscopic sphincterotomy.<br/>
'''Educational Objective:''' Pancreatic divisum is the most common congenital variant of pancreatic ductal configuration. It is caused by the failure of fusion of the distal and ventral pancreatic ducts leading to 2 distinct ducts.<br/>
'''References:''' Manfrendi R, Costamagna G, Brizi MG, et al. Pancreas divisum and "santorinicele": diagnosis with dynamic MR cholangiopancreatography with secretin stimulation. Radiology. 2000;217:403-408. +
Different parts of the GI tract are unique for the presence of different histological aspects that correspond with the function of every part. The histological appearance of esophagus is characterized by nonkeratinized stratified squamous epithelium as shown in the image above. In contrast, the stomach is lined by gastric glands. Generally, the duodenum, jejunum, and ileum have similar histological appearance but each has a unique features that differentiate them from each other. They contain villi and microvilli that increase the absorptive surface of the small intestine, crypts of Lieberkuhn, and plicae circulares. The hallmark of the duodenum is the presence of Brunner's glands. Finally, the colon contains crypts and abundant goblet cells but no villi.<br/>
'''Educational Objective:''' The histological appearance of the esophagus is characterized by nonkeratinized stratified squamous epithelium.<br/>
'''References:''' Kumar V, Abbas AK, Fausto N et al. Robbins and Cotran Pathologic Basis of Disease, Professional Edition, Expert Consult - Online. Elsevier Health Sciences; 2009. +
The patient presents with symptoms typical of direct inguinal hernia. Direct hernias bulge through the external superficial inguinal ring and occur secondary to abdominal wall weakness that occurs with old age. Direct hernias are most commonly present in the Hasselbach's triangle, a unique region that lies low in the posterior aspect of the anterior abdomen delineated medially by the rectus abdominis muscle, inferiorly by the inguinal ligament, and laterally by the inferior epigastric vein and artery. In contrast, indirect inguinal hernias are common at young age; they occur due to the persistence of the processus vaginalis. Patients present with a bulge protruding from the internal deep inguinal ring.<br/>
'''Educational Objective:''' The rectus abdominis muscle occupies the medial aspect of the Hasselbach's triangle, the most common anatomical location of direct hernias.<br/>
'''References:''' Morton D, Foreman KB, Albertine K. Gross Anatomy: The Big Picture. McGraw Hill Professional; 2011. +
Gastric inhibitory peptide (GIP), also known as glucose-dependent insulinotropic peptide is a GI hormone secreted by K cells in the duodenum and the jejunum. GIP is considered an incretin, i.e. a molecule that increases the amount of insulin released from pancreatic beta cells of the islets of Langerhans. As such, oral GIP secretion following the oral intake of fatty acid, amino acids, and glucose, leads to an "incretin effect" due to the increased secretion of insulin following release of GIP in the GI tract. The elevation in insulin levels is not seen in I.V. infusion of GIP. As a result, "incretin effect" is seen following oral GIP but not I.V. GIP, which explains the variation in plasma concentration of compound X (insulin) during each experiment. In addition to GIP, another incretin is GLP-1 (glucagon-like peptide-1) hormone. Both incretins migrate in the circulation to the beta cells of the pancreas, their target cells to stimulate insulin secretion. It has been postulated the incretin effect is defective in type 2 diabetes mellitus (T2DM); GLP-1 analogs are currently pharmacologic options for patients with T2DM.<br/>
'''Educational Objective:''' GIP induces insulin secretion in a phenomenon called the "incretin effect". With increased insulin production and secretion, C-peptide, a by-product of insulin production also increases. Although GIP decreases GI motility, it is not associated with changes in motilin.<br/>
'''References:''' Martin JH, Deacon CF, Gorrell MD, Prins JB. Incretin-based therapies - review of the physiology, pharmacology and emerging clinical experience. Intern Med J. 2011;41(4):299-307. +
Mallory-Weiss syndrome (MWS) is a frequent cause of hematemesis. It is characterized by upper GI bleeding due to the longitudinal mucosal laceration of the distal part of the esophagus or the proximal part of the stomach, the gastric cardia, that causes hematemesis following a submucosal arterial bleed. MWS is commonly caused by violent vomiting and retching in alcoholics and bulimics that cause an increase in intra-abdominal pressure, which is strong enough to cause the gastric cardia to protrude into the thoracic cavity through the hiatus and cause a longitudinal laceration. MWS tear accounts for approximately 15% of all cases of upper GI bleeding. Blood is classically arterial in origin and is bright red. The presentation of patients can vary from one episode of hematemesis to hypotension and progressive shock. depending on the extent of bleeding. Initial management is supportive as the majority of these tears resolve without intervention. Endoscopic ligation is reserved for patients with prolonged bleeding.<br/>
'''Educational Objective:''' Mallory-Weiss syndrome (WMS) is characterized by the longitudinal laceration in the distal esophagus or the gastric cardia. It is a common cause of hematemesis in alcoholics and bulimics.<br/>
'''References:''' Morales P, Baum A. Therapeutic alternatives for the Mallory-Weiss tear. Curr Treat Options Gastroenterol. 2003;6(1):75-83. +
Membranous nephropathy (MN) or membranous glomerulonephritis (MGN) is a common glomerulonephritis that usually presents with nephrotic-range proteinuria, edema, and hypertension. MN is generally classified as primary (idiopathic) or secondary to other systemic disease, such as infections, malignancies, or vasculitides. Primary MN has been associated with the presence of a newly discovered phospholipase A2 receptor (PLA2R) nephrotigenic antigen on the membrane surface of glomerular podocytes and anti-PLA2R antibodies. Kidney biopsy remains the gold standard for the diagnosis of MN, which demonstrates subepithelial deposits with capillary wall thickening and IgG deposition under immunofluorescence. On electron microscopy, MN shows a "spike and dome" appearance with subepithelial deposits. While MN is widely considered a chronic condition with a waxing and waning course, it is usually self-limited in the majority of cases. Heavy proteinuria, a significant marker of prognosis, indicates the need for intervention, usually with corticosteroids and immunosuppressive therapy.<br/>
'''Educational Objective:''' Anti-phospholipase A2 receptor antibodies are nephritogenic antibodies associated with membranous nephropathy. They are classically present in sera of patients with membranous nephropathy and as IgG deposits on podocyte surfaces.<br/>
'''References:''' Beck LH Jr, Bonegio RG, Lambeau G, et al. M-type phospholipase A2 receptor as target antigen in idiopathic membranous nephropathy. N Engl J Med. 2009;361(1):11-21.<br>
Qin W, Laurence H, Beck LH Jr, Zeng C, et al. Anti-phospholipase A2 receptor antibody in membranous nephropathy. J Am Soc Nephrol. 2011;22:1137-1143.<br>
First Aid 2014 page +
Early wound healing is characterized by the presence of the inflammatory cells that produce growth factors to stimulate the migration and proliferation of fibroblasts. Fibroblasts are secretory cells that produce extracellular matrix abundant in collagen. Later during the healing process (proliferation stage) , fibroblasts then differentiate into myofibroblasts to start the process of contracture. Eventually, myofibroblasts normally disappear. Their persistence at the site is associated with cancers, fibromatoses, and fibrotic diseases. Fibroblasts are recognized by immunohistochemical analysis by their spindle-shaped appearance and their strong positivity for vimentin stain.<br/>
'''Educational Objective:''' Vimentin stains fibroblasts, a component of connective tissue that is responsible for the early wound healing.<br/>
'''References:''' Goodpaster T, Legesse-Miller A, Hameed MR, et al. An immunohistochemical method for identifying fibroblasts in formalin-fixed, paraffin-embedded tissue. J Histochem Cytochem. 2008;56(4):347-358.<br>
First Aid 2014 page 78 +
Angina is the most common presentation of aortic stenosis, but it can also present as syncope or heart failure. A crescendo decrescendo systolic ejection murmur is characteristic of aortic stenosis. The murmur increases in intensity with elevation of the legs, and squatting, but decreases in intensity on valsalva maneuver, standing and handgrip. Delayed carotid upstroke is also seen in aortic stenosis. Transthoracic echocardiogram is the best initial diagnostic test and diuretics are the preferred initial therapy. Definitive therapy is valve replacement.
'''Educational Objective:''' A crescendo decrescendo systolic ejection murmur is characteristic of aortic stenosis.
'''References:''' Page 63, 64 Master the boards step 3 2009 edition, Page 86,87,88,89,90,91,92 Master the boards step 2 CK second edition<br/>
'''Educational Objective:''' <br/>
'''References:''' +