USMLE Step 1 practice questions — 10 free

Facial pain, headache, and nasal eschar in a patient with likely diabetic ketoacidosis (pH 7.1, positive ketones, and dry mucous membranes in a ‘young patient with unintended weight loss) are highly suggestive of mucormycosis, caused by Mucor or Rhizopus, among others. Most cases are thinocerebral. The infection (acquired by spore inhalation) ascends from the nasal passage to the sinuses/orbits and then sometimes to the brain, leading to confusion, neurological deficits. and death_ The increased incidence of mucormycosis in diabetics could be due to the ketone g = <a > 2. of 1 2 & 7 wa Ss ft, = Rene enti Previous Next FullScreen Tutorial ~~ Lab Values Noles Calculator Reverse Color TextZoom —_Sellings Facial pain, headache, and nasal eschar in a patient with likely diabetic ketoacidosis (pH 7.1, positive ketones, and dry mucous membranes in a young patient with unintended weight loss) are highly suggestive of mucormycosis, caused by Mucor or Rhizopus, among others. Most cases are rhinocerebral. The infection (acquired by spore inhalation) ascends from the nasal passage to the sinuses/orbits and then sometimes to the brain, leading to confusion, neurological deficits, and death. The increased incidence of mucormycosis in diabetics could be due to the ketone reductase activity of Rhizopus (allowing it to survive in an acidotic, hyperglycemic environment) and possibly to the release of iron from binding proteins during ketoacidosis (facilitating Rhizopus growth). Histologic examination is necessary for diagnosis. The fungi appear as broad ribbon-like nonseptate hyphae with right-angle branching. Tissue invasion is seen along blood vessels; vascular thrombosis and tissue necrosis can occur. A black necrotic eschar in the nasal cavity is characteristic. Management includes amphotericin B and surgical debridement. Mucormycosis (commonly seen in diabetics) must be differentiated from invasive aspergillosis causing rhinosinusitis (commonly seen in neutropenic patients). On light microscopy, Aspergillus is seen ‘as septate narrow hyphae with sharp-angle branching. (Choice A) Blood cultures are usually negative in mucormycosis. They can be useful in diagnosing candidemia (clinical manifestations range 7 from low-grade fever to multiorgan failure, occasionally with characteristic chorioretinitis and clustered pustular skin lesions). + 18 (Choice B) Lumbar puncture helps to diagnose cryptococcal meningitis, a fungal infection that typically has an indolent presentation and usually + 19 affects patients with AIDS. India ink staining of cerebrospinal fluid reveals the classic encapsulated yeast of Cryptococcus neoformans. +» 20 rm (Choice D) Ophthalmoscopy is useful for the diagnosis of Candida endophthalmitis, which typically presents with impaired visual acuity. 12 (Choices E and F) Serologic testing is important in the diagnosis of allergic bronchopulmonary asperuillosis (ABPA), where increased titers of IgE 23 and antibodies to Aspergillus fumigatus are seen. Skin hypersensitivity testing is also useful. However, the typical presentation of ABPA is aaa recurrent episodes of fever and bronchial obstruction in a patient with asthma. 25 Educational objective: aS Facial pain, headache, and black necrotic eschar in the nasal cavity in a patient with diabetic ketoacidosis are highly suggestive of mucormycosis 7 Histologic examination of the affected tissue is necessary to confirm the diagnosis. The fungi show broad nonseptate hyphae with right-angle 28 branching. Treatment consists of surgical debridement and antifungal therapy. 29 g 31 TUTOR "=== <a > ee Olena es 7 @ 8 Cs antl atatlt Previous Next FullScreen Tutorial Lab Values_—Noles_ Calculator Reverse Color_—TextZoom —_Sellings 4 Histologic examination is necessary for diagnosis. The fungi appear as broad ribbon-like nonseptate hyphae with right-angle branching. Tissue 5 invasion is seen along blood vessels; vascular thrombosis and tissue necrosis can occur. A black necrotic eschar in the nasal cavity is 6 characteristic. Management includes amphotericin 8 and surgical debridement. Mucormycosis (commonly seen in diabetics) must be 7 differentiated from invasive aspergillosis causing rhinosinusitis (commonly seen in neutropenic patients). On light microscopy, Aspergillus is seen 8 as septate narrow hyphae with sharp-angle branching. (Choice A) Blood cultures are usually negative in mucormycosis. They can be useful in diagnosing candidemia (clinical manifestations range + 10 from low-grade fever to multiorgan failure, occasionally with characteristic chorioretinitis and clustered pustular skin lesions) (Choice B) Lumbar puncture helps to diagnose cryptococcal meningitis, a fungal infection that typically has an indolent presentation and usually affects patients with AIDS. India ink staining of cerebrospinal fluid reveals the classic encapsulated yeast of Cryptococcus neoformans. (Choice D) Ophthalmoscopy is useful for the diagnosis of Candida endophthalmitis, which typically presents with impaired visual acuity. (Choices E and F) Serologic testing is important in the diagnosis of allergic bronchopulmonary aspergillosis (ABPA), where increased titers of IgE and antibodies to Aspergillus fumigatus are seen. Skin hypersensitivity testing is also useful. However, the typical presentation of ABPA is recurrent episodes of fever and bronchial obstruction in a patient with asthma. . 18 ‘o Educational objective: _ Facial pain, headache, and black necrotic eschar in the nasal cavity in a patient with diabetic ketoacidosis are highly suggestive of mucormycosis. y Histologic examination of the affected tissue is necessary to confirm the diagnosis. The fungi show broad nonseptate hyphae with right-angle se branching. Treatment consists of surgical debridement and antifungal therapy. © 22 8 References ae « Novel perspectives on mucormycosis: pathophysiology, presentation, and management + 25 oar Microbiology _—iInfectious Diseases. Mucormycosis a Subject system Topic 28 ae 30 Block Time Remaining: 0 31 TUTOR a = A

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Patterns of tissue necrosis Setting: Question Previous Patterns of tissue necrosis Type Etiology Morphology + Necrotic tissue is digested by hydrolytic enzymes into a viscous : : fluid eiquatnctive ae aes il tections (e9) gangrene) © Infected abscess fluid is creamy yellow due to dead shes leukocytes (pus) © Brain infarcts resolve into CSF-filed spaces Fibrinoid | « Hypertension + Damaged vessels leak fibrin/immune complexes necrosis | + Vasculitis + Eosinophilic layer of proteinaceous material in vessel walls «Free fatty acids released by active enzymes (eg, lipases) or Fatnecrosis. |" Actte pancreatitis mechanical damage + Trauma (subcutaneous adipose tissue) «Fatty acids combine with calcium, forming chalky-white deposits (saponification) ae + Friable, cheeselike material composed of cell fragments & Caseous | bis ali gat mae aria ‘amorphous proteinaceous debris necrosis prom se Mcrae ts + Surrounded by epithelioid macrophages & giant cells Cryptococcus, Coccidioides) » (granuloma) «+ Tissue architecture is preserved due to denaturation of lytic os ae ve (i revereie echennciany cuss ChS Be wea necrosis © Cells are anucleate with eosinophilic cytoplasm © Leukocytes eventually infiltrate & digest necrotic tissue Setting:

Diabetes causes impaired autoregulation of glomerular blood flow, leading to significant elevations of intraglomerular pressures and chronic glomerular injury. Patients with diabetes and hypertension are at especially high long-term risk for chronic kidney disease. Angiotensin-converting enzyme (ACE) inhibitors (eg, lisinopril) cause preferential dilation of the glomerular efferent arteriole, lowering intraglomerular pressures and reducing the risk of chronic glomerular injury. In addition to converting angiotensin | to angiotensin Il, ACE normally degrades bradykinin and substance P_ Inhibition of ACE leads to elevated + ~ ee Feedback Suspend = = Item 22 of 40 ~ Vv eee i @) - 0.25 a a EYE £3

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‘Sleep deprivation is common among physicians and can have a profound effect on patient safety. Sleep science has demonstrated "dose- dependent" effects of sleep deprivation on physician cognitive performance and risk of medical errors. Impairments in cognitive performance and motor skills typically manifest after 17 hours of wakefulness and are comparable to those seen in an alcoholintoxicated individual._Although the = Item 11 of 13 mY mac <q Se ie (O) al i=) = la Qa ‘Suspend — Item 11 of 13 mY mark <q Se Real (O) al i=) = la Ga &

This patient with Crohn disease initially responded to treatment with adalimumab but subsequently experienced treatment failure with a relapse of symptoms after nearly a year of therapy. Adalimumab is a recombinant human IgG that binds tumor necrosis factor-alpha (TNF-alpha), an inflammatory cytokine involved in promoting leukocyte migration, neutrophil and macrophage function, and granuloma integrity. Adalimumab prevents TNF-alpha from associating with its cell-surface receptors, blocking its pro-inflammatory effects. TNF-alpha inhibitors are used for a Ga\A) Text “oom - 1 fi _ ttem1 of 38 6 ~s om tn fe tl mB Le ee ee ee ee ee ee So 6 6& Sw om Fo & WwW mM FP S&S 6 © SN Om wo & Ww mM HF & ee Ld ji 5 =& GA & oe m V7 Mark Lat ry al = ‘A Cw AA

This patient's dysuria, suprapubic tenderness, and urinalysis abnormalities suggest acute simple cystitis. Women are at much greater risk than ‘men for urinary tract infections (UTIs) because they have a shorter urethra lying in close proximity to the anus and vaginal introitus, which allows enteric flora (eg, Escherichia coli) to spread to the vaginal opening and subsequently ascend through the urethra to the bladder. The major tisk factor in otherwise healthy young women is recent sexual intercourse. Although urinating after intercourse flushes bacteria from the lower urinary tract (thereby reducing UTI risk), patients may still develop a UTI (Choice B) Hematologic infections generally enter the urinary tract through the glomeruli and cause pyelonephritis. Although pyuria and g 3 Ss - &A eile, mY Mark a4 a