Question | Answer |
What are the most common causes of impetigo? | Staph aureus (most common) and Strep pyogenes |
What is the cause of bullous impetigo? | Staph aureus - the phage group II production locally |
What protein is cleaved in bullous impetigo that causes the blister? | desmoglein 1 |
What is the clinical presentation of non-bullous impetigo? | -single erythematous macule that rapidly evolves into a vesicle or pustule and rapidly spreads into a "honey-colored" crust |
What is the potential side effect of 5% of causes of nonbullous impetigo caused by strep pyogenes? | post-strep glomerulonephritis
(risk is not changed by giving antibiotics) |
What patient population does bullous impetigo occur in? | usually neonates |
What is the histology of impetigo? | -small neutrophilic vesiculopustules in the epidermis
-spongiosis
-intense infiltrate of neutrophils and lymphs in the upper dermis |
What is the treatment of non-complicated impetigo? | mupirocin
retapamulin |
What is the most common cause of bacterial folliculitis? | Staph aureus |
What is sycosis barbae? | a type deep of folliculitis with large erythematous papules with a central pustule, sometimes coalescing to form pustules and crusts |
How can you eradicate staph aureus nasal carriage? | mupirocin ointment BID to the nares x 5-10 days |
What is the most common presentation of MRSA? | furuncolosis |
What is the cause of methiciliin resistance in staph? | altered penicillin-binding protein (PBP2a) with decreased affinity for beta-lactams |
What is the D test (double-disk diffusion)? | Tests for inducible resistance to clindamycin; if the "erm" gene is present, and the bug is resistant to erythromycin, then resistance to clindamycin will develop |
What are the most common causes of blistering distal dactylitis? | group A strep and staph aureus |
Where is the location of blistering distal dactylitis? | volar fat pad of the finger or toe with occasional involvement of the nail fold |
What is the treatment of blistering distal dactylitis? | 10 day course of antibiotics and drainage |
What patient population typically gets blistering distal dactylitis? | children aged 2-16 years (from nose-picking) |
What is the cause of ecthyma? | strep pyogenes |
What are the clinical features of ecthyma? | initial vesiculopustule that enlarges and develops a hemorrhagi crust with a "punched-out" appearance and necrotic base |
What is the most common location of ecthyma? | lower extremity |
What is the cause of staph scalded skin syndrome? | phage group II strains 55 and 71 |
What protein is cleaved in SSSS? | desmoglein 1 |
What host factors contribute to the development of SSSS? | -decreased renal clearance of the toxin
-lack of toxin-neutralizing antibodies |
Where is the epidermal split in SSSS? | within or below the stratum granulosum |
What is the prodrome of SSSS? | malaise, fever, irritability, tenderness of the skin, rhinorrhea, conjunctivitis
-erythema of the head with variable facial edema that occurs 48 hours before the onset |
What are the differences between staph and strep toxic shock syndromes? | patients with strep typically have a localized soft tissue infection with lacerations, bites, etc
-strep often has positive blood cultures (staph does not)
-mortality is much higher for strep (50-60%) |
What are the clinical features of toxic shock syndrome? | -fever
-rash (diffuse macular erythema)
-desquamation
-hypotension
-involvement of: GI, CNS, renal, hepatic, mucous membranes |
What antibiotic actually suppresses protein and toxin production from staph? | clindamycin |
What bacteria is the cause of scarlet fever? | group A beta hemolytic strep, specifically strep pyrogenic exotoxins A,B,C |
What is the typical patient population for scarlet fever? | children younger than 10 (after 10 most of the population has developed anti-strep pyrogenic toxin antibodies) |
What type of illness does scarlet fever usually follow? | tonsillitis or pharyngitis |
What are the clinical features of scarlet fever? | -sore throat, headache, malaise, chills, anorexia, nausea, and high fever, abdominal pain, vomiting
-cutaneous eruption begins 12-48 hours later as blanchable erythema on the neck, chest, and axillae with small papules that feel like sandpaper |
What are the cutaneous features of scarlet fever? | -"sunburn with goose pimples" that develops 12-48 hours after the onset of the illness
-Pastia's lines (linear petechial streaks) in the axillae, antecubital, and inguinal areas
-flushed cheeks
-circumoral pallor
-strawberry tongue
-desquamation |
What are Pastia's lines? | linear petechial streaks that occur in the axillae, antecubital fossae, and inguinal area with scarlet fever |
Where does the desquamation in scarlet fever classically occur? | palms and soles |
What is the treatment of scarlet fever? | amoxicillin |
What types of strep cause strep toxic shock syndrome? | M types 1 and 3 of group A strep |
What molecules do superantigens bind to? | MHC class II on APCs and VB region of the T cell receptor |
What is the typical source for strep toxic shock syndrome? | soft tissue infection with sudden onset of pain in an extremity |
What is the treatment of choice for strep toxic shock syndrome? | clindamycin |
Erysipelas is also known as? | St. Anthony's fire |
What is erysipelas? | superficial variant of cellulitis caused by group A strep |
What is the most common cause of erysipelas? | group A strep |
What is the typical patient population that is affected by erysipelas? | -very young
-elderly
-the debilitated (esp lymphedema or chronic cutaneous ulcers) |
What is the classic location for erysipelas? | face |
What is the clinical appearance of erysipelas? | sharply marginated, erythematous plaque that is slightly tender |
What is the treatment of choice of erysipelas? | penicillin |
What patient population often has recurrent erysipelas? | patients with lymphedema |
What are the clinical features of perianal strep? | -sharply demarcated bright red erythema
-perianal pruritus
-painful defectation
-blood-streaked stools
-anal leakage |
What clinical infection often precedes perianal strep? | strep pharyngitis |
What organism can cause positive blood cultures in cellulitis? | H. influenzae |
What is the most common organism involved in pyomyositis? | staph aureus |
What is the diagnostic method of choice of pyomyositis? | MRI |
What is the most common cause of botryomycosis? | staph aureus |
What are the cutaneous features of botryomycosis? | cutaneous and subcutaneous nodules, ulcers, and verrucous plaques that discharge purulent yellow granules |
What are the histologic features of botryomycosis? | chronic inflammatory reaction with fibrosis and foreign body giant cells
-granular bodies (grains) that are bacteria, cells, and debris.
-have basophilic centers and eosinophilic periphery |
What is the Splendore-Hoeppli phenomenon? | -intensely eosinophilic material that radiates around organisms
-caused by a local antigen-antibody reaction |
What is the treatment of botryomycosis? | excision or surgical debridement |
What are Osler's nodes? | TENDER, erythematous papules and noules on the finger pads and thenar/hypothenar eminences
-caused by immune complex deposition and small vessel vasculitis |
What are Janeway lesions? | PAINLESS, small hemorrhagic macules on the palms and soles
-caused by septic emboli with microabscesses |
What is the most common organism implicated in gas gangrene? | Clostridium perfringens (>80%) |
How is the exudate in anaerobic cellulitis and gas gangrene described? | thin, dark gray-brown, (dirty dishwater) |
What toxins are responsible for gas gangrene? | alpha toxin and perfringolysin |
Corynebacterium are gram positive or negative? | gram positive rods |
What organism causes erythrasma? | Corynebacterium minutissimum |
Where are the common locations for erythrasma? | groin, axillae, intergluteal fold, inframammary areas (warm, moist environments) |
What are the clinical features of erythrasma? | pink to red, well-defined patches that are covered with fine scales and have associated wrinkling. with time, the color fades to brown -asymptomatic |
How does erythrasma appear under the Wood's lamp? | bright coral red |
What causes the fluorescent color of erythrasma? | porphyrin produced by the bacteria |
What culture medium is used to grow Corynebactrium? | Tissue Culture Medium 199 |
What are topical therapies for erythrasma? | 20% aluminum chloride, clindamycin, erythromycin, azoles, Whitfield ointment |
What is the most common bacterial infection of the foot? | Interdigital erythrasma (chronic macerated fissuring) |
What organism causes pitted keratolysis? | Kytococcus sedentarius |
What enzymes are produced by Kytococcus sedentarius to cause pitted keratolysis? | serine proteases (K1 and K2) that degrade keratin |
What are the clinical features of pitted keratolysis? | 1-7mm crater like depressions within the stratum corneum of the weight-bearing regions of the soles -no associated erythema -often unnoticed by the patient |
How does fluorescence of pitted keratolysis appear? | it doesn't fluoresce |
What are treatment options for pitted keratolysis? | topical erythromycin, clindamycin, mupirocin, tetracycline, or azoles |
What organism causes trichomycosis axillaris? | corynebacterium tenuis |
What is the clinical appearance of trichomycosis axillaris? | yellow, red or black adherent concretions on the axillary or pubic hair -characteristic odor -sweat can turn red and stain clothing |
How does trichomycosis axillaris fluoresce with a Wood's lamp? | pale yellow |
What is the treatment for trichomycosis axillaris? | shave the hair and topical erythromycin or clindamycin |
How does cutaneous diphtheria present? | punched out ulcer with a gray pseudomembrane "eschar" |
What is the most common site of cutaneous diphtheria? | acral locations |
What positive impact does cutaneous diptheria have for unvaccinated children? | -can be a form of immunization as the toxin is very slowly absorbed from skin lesions and induces high levels of antibodies |
What 3 ways is anthrax transmitted? | 1) inhalation 2) ingestion 3) cutaneous inoculation |
How is anthrax typically acquired? | occupational exposure with infected animal carcasses (woolsorter's disease) |
Is anthrax gram positive or negative? | gram positive sporulating rod |
What is the function of "edema toxin" | impairs neutrophil function and affects water homeostasis, leading to edema |
What is the function of "lethal toxin"? | causes release of TNF-alpha and IL-1B |
What 3 toxin components does anthrax require for virulence? | protective antigen, lethal factor, and edema factor (combine to form lethal toxin and edema toxin) |
Is cutaneous anthrax painful or painless? | PAINLESS |
What are the clinical features of cutaneous anthrax? | -pupuric macule or papule that looks like an insect bite and then vesiculates and forms non-pitting edema -the vesicle ulcerates and becomes hemorrhagic and depressed with a painless black eschar -the eschar dries over 1-2 weeks - no scar |
How do anthrax spores appear in culture? | "jointed bamboo rod" cells with "curled hair" appearing colonies |
Do systemic symptoms commonly occur with cutaneous anthrax? | NO |
What is the antibiotic of choice for cutaneous anthrax? | ciprofloxacin 500mg bid |
How is cutaneous anthrax treated? | ciprofloxacin- the antibiotic does not alter the evolution of the skin lesions but prevents systemic infection |
What bacterial infection should be suspected in a neutropenic patient with a single necrotic bulla? | bacillus cereus |
What is the causative organism of erysipeloid? | Erysipelothrix rhusiopathiae |
What occupation is most likely to get erysipeloid? | fishermen or people who prepare meat, poultry or fish |
What is the classic clinical presentation of erysipeloid? | localized erythema/cellulitis that can be pruritic or painful and spares the terminal phalanges |
What is the drug of choice for treatment of erysipeloid? | Penicillin |
What body parts are involved/ not involved in erysipeloid? | commonly on the hands with involvement of the finger/web spaces and sparing of the distal phalanx |
What types of infections does listeria cause? | - GI illness (in elderly, pregnant women, and immunocompromised) -meningitis in immunocompromised -neonatal meningitis or septicemia -primary cutaneous disease (usually in vets) |
What is the antibiotic of choice for listeria? | Ampicillin |
What are risk factors for meningococcemia infections? | asplenia and terminal complement deficiency (C5-9) |
What is the source of N meningitidis virulence? | polysaccharide capsule |
Infection with what organism classically causes purpura with irregular outline and central gunmetal gray color? | Neisseria |
What percent of patients with acute meningococcemia develop a petechial eruption? | 30-50% |
What is the histologic appearance of skin biopsies in patient's with disseminated meningococcemia? | LCV and thrombosis with organisms within the vessels |
What are the cutaneous features of disseminated meningococcemia? | -petechial eruption -retiform purpura and ischemic necrosis -purpura with a gunmetal gray appearance |
What are Rocha-Lima inclusions? | masses of intracytoplasmic Bartonella organisms |
What 3 Bartonella species cause human infection?` | 1) B. henselae 2) B. quintana 3) B. bacilliformis |
What two organisms can cause bacillary angiomatosis? | B. henselae and B. quintana |
Bartonellosis is also known as ? | Carrion's disease |
What is the vector of bartonellosis? | Phlebotomine sandfly |
Where does bartonellosis occur? | Peru, Ecuador, southwestern Colombia |
What are the two phases of Bartonellosis? | 1) Oroya fever 2) verruga peruana |
What are the clinical manifestations of Oroya fever? | sudden onset of dyspnea, weakness, pallor, tachycardia, fever, thirst, anorexia, arthralgias, headache |
What are the lab abnormalities seen in Oroya fever? | drop in RBC count with massive hemolysis and variable immunodeficiency |
What secondary infection are patients with Oroya fever particularly susceptible to? | Salmonella enterica |
What is verruga peruana? | cutaneous nodules that develop on the head and extremities of patients who have recovered from Oroya fever |
What is the clinical appearance of verruga peruana? | bright red papulesa nd nodules that appear within erythematous patches -found on the head and extremities -heals without scarring |
What is the histologic appearance of a verruga peruana? | may look like a pyogenic granuloma or Kaposi sarcoma |
What organism is the causative agent of Cat Scratch Disease? | Bartonella henselae |
What are the clinical manifestations of Cat Scratch Disease? | -red papule or crusted pustule develops at the site of inoculation -single, large, tender, lymph node with erythema and swelling usually in the axilla |
What is the treatment of Cat Scratch Disease? | typically no treatment required; complicated cases may require azithromycin or doxycycline |
What are the systemic symptoms associated with Cat Scratch Disease? | -usually no systemic symptoms -may occasionally have fever, malaise, fatigue |
What patient population is typically affected by bacillary angiomatosis? | HIV patients |
What are the clinical features of bacillary angiomatosis? | superficial angiomatous papules and nodules that can look like a pyogenic granuloma |
What is bacillary peliosis hepatis? | bacillary angiomatosis of the liver caused by B henselae (not quintana) |
What is bacillary peliosis splenis? | bacillary angiomatosis of the spleen |
What are the histologic features of bacillary angiomatosis? | lobular proliferations of capillaries and venules with plump, endothelial cells -lots of neutrophils and leukocytoclasia -interstitial clumps of bacteria |
What is the antibiotic of choice to treat bacillary angiomatosis? | erythromycin |
What organism is the causative agent of trench fever? | B. quintana |
What is the vector of trench fever? | human body louse (Pediculosis humanus) |
How is Brucellosis transmitted? | consumption of unpasteurized milk products or direct contact with animal parts |
What are the cutaneous manifestations of Brucellosis? | (occur in <10% of patients) disseminated eruption of violaceous papulonodules or morbilliform eruptions, E nodosum |
What are the typical clinical manifestations of Brucellosis? | nonspecific signs and symptoms of fever, chills, malaise, headache, arthralgias, etc |
What is the first-line treatment of Brucellosis? | doxycycline |
What is the causative organism of Glanders? | Burkholderia mallei |
What animals does Glanders primarily affect? | donkeys, mules, and horses |
What are the 4 clinical forms of Glanders? | 1) septicemia 2) localized 3) pulmonary 4) chronic |
What are the clinical features of localized Glanders? | nodule, pustule or vesicle surrounded by hemorrhagic edema at the inoculation site that sloughs and forms a gray-brown base |
What are the cutaneous features of chronic Glanders infection? | painful subcutaneous and intramuscular abscesses |
What is the causative organism of Melioides? | Burkholderia pseudomallei |
What types of infections can Melioidosis cause? | -localized cutaneous -pulmonary disease -acute septicemia -abscesses and granulomas -cellulitis, echthyma, purpura, pustulese |
What is the most common organism involved in malakoplakia? | E. coli |
What is the most common location on the skin for malakoplakia? | perianal area |
What is the most common location overall for malakoplakia? | GU tract |
What are Michaelis-Gutmann bodies | intracytoplasmic laminated concretions that are accumulations of calcified, iron-containing phagolysosomes in Malakoplakia |
What are von Hansemann cells? | Large macrophages that contain Michaelis-Gutmann bodies in Malakoplakia |
What is malakoplakia? | chronic granulomatous inflammation with macrophages that are unable to appropriately phagocytose and kill bacteria in immunocompromised hosts |
What is the treatment of malakoplakia? | surgical excision or long-term antibiotics |
What is the causative organism involved in Tularemia? | Francisella tularensis |
What are the reservoirs for F. tularensis? | rabbits, deer flies, and ticks |
What is the most common form of Tularemia? | ulceroglandular |
What are the clinical features of ulceroglandular tularemia? | lymphadenopathy that may suppurate and an erythematous, indurated, punched-out ulcer that may last for several weeks |
What is the antibiotic of choice for Tularemia? | streptomycin |
Infection with what organism can cause facial cellulitis with a violaceous hue in young children following an upper respiratory tract infection? | Haemophilus influenze |
What is the causative organism of Rhinoscleroma? | Klebsiella rhinoscleromatis |
What are Mikulicz cell? | large, vacuolated non-lipidized histiocytes with intracellular bacteria seen in Rhinoscerloma |
What two types of cells are commonly seen in Rhinoscleroma? | Mikulicz cells (large histiocytes with intracellular bacteria) and Russell bodies (plasma cells with lots of Igs) |
What are the 3 stages of Rhinoscleroma? | 1) rhinitic 2) granulomatous/infiltrative 3) sclerotic |
What are the features of the rhinitic phase of Rhinoscleroma? | -rhinitis with purulent rhinorrhea and nasal obstruction |
What are the clinical features of the granulomatous phase of rhinoscleroma? | granulomatous nodules the form in the nose, pharynx, and larynx -epistaxis -destruction of the nasal cartilage |
What are the clinical features of the sclerotic phase of Rhinoscleroma? | nodules replaced by fibrous tissue and resultant scarring and stenosis of the airway |
What is the causative organism of typhoid fever? | Salmonella typhi |
What are the cutaneous manifestations of typhoid fever? | "rose spots"- pink, blanching, slightly elevated papules on the anterior trunk in groups of 5-15 lesions and come in crops during the 2nd to 4th weeks of the illness |
What is the drug of choice to treat typhoid fever? | quinolones |
What is the causative organism of Rat-Bite Fever? | Streptobacillus moniliformis |
What is the classic triad of Rat Bite Fever? | 1) fever 2) migratory polyarthritis 3) rash |
What are the cutaneous manifestations of Rat Bite Fever? | acrally distributed morbilliform eruption on the palms and soles with papules, petecthia, vesicles, pustules 2-4 days following the onset of the fever |
What is the drug of choice to treat Rat Bite Fever? | Penicillin |
What is the causative organism involved in the plague? | Yersinia pestis |
What are the 3 types of plague? | 1)bubonic 2)septicemic 3)pulmonic |
What is the causative organism of typhoid fever? | Salmonella typhi |
What are the cutaneous manifestations of typhoid fever? | "rose spots"- pink, blanching, slightly elevated papules on the anterior trunk in groups of 5-15 lesions and come in crops during the 2nd to 4th weeks of the illness |
What is the drug of choice to treat typhoid fever? | quinolones |
What is the causative organism of Rat-Bite Fever? | Streptobacillus moniliformis |
What is the classic triad of Rat Bite Fever? | 1) fever 2) migratory polyarthritis 3) rash |
What are the cutaneous manifestations of Rat Bite Fever? | acrally distributed morbilliform eruption on the palms and soles with papules, petecthia, vesicles, pustules 2-4 days following the onset of the fever |
What is the drug of choice to treat Rat Bite Fever? | Penicillin |
What is the causative organism involved in the plague? | Yersinia pestis |
What are the 3 types of plague? | 1)bubonic 2)septicemic 3)pulmonic |
What are the clinical features of the bubonic plague? | the site of inoculation may develop a pustule or ulcer followed by painful LAD and suppuration |
What is the treatment of choice for plague? | streptomycin |
What organism should be suspected in a fisherman with a painful erythematous, edematous cellulitis that rapidly progresses to hemorrhagic bullae? | Vibrio vulnificus |
What are the risk factors for Vibrio vulnifus infections? | chronic liver disease, diabetes, or exposure to raw seafood or seawater |
What are the clinical features of Vibrio septicemia? | -fever, chills, nausea, vomiting, diarrhea, abdominal cramps, hypotension -erythematous to pupuric macules and vesicles with hemorrhagic bullae and necrotic ulcers |
What is the first-line treatment of Vibrio vulnificus? | doxycycline + Rocephin |
What is the vector of Lyme disease? | Ixodes tick |
What organisms are the most common cause of Lyme disease in Europe? | Borrelia garinii and Borrelia afzelii |
How long does a tick have to be attached to transmit Lyme disease? | usually over 24 hours |
What is the classic cutaneous manifestation of Lyme disease? | erythema migrans |
What organisms cause Borrelia lymphocytomas? | B. garinii and B afzelii (not found in the US) |
Where are the classic locations for Borellia lymphocytomas? | earlobes of children and nipple/areola of adults |
What percent of patients with Lyme disease in Europe develop acrodermatitis chronica atrophicans? | 10% |
What is thought to be the cause of acrodermatitis chronica atrophicans? | long-term persistence of the spirochete in the skin |
What are the clinical features of the early stage of acrodermatitis chronica atrophicans? | erythematous to violaceous plaques and nodules develop on acral extremities -follows a waxing and waning course over years |
What are the clinical features of the late stage of acrodermatitis chronica atrophicans? | -glistening "cigarette paper" appearance with prominent blood vessels -hypo or hyper pigmentation, pain, pruritus, hyperesthesia, paresthesia |
What are the treponemal tests that are specific for treponemal infection? | TPHA, FTA-ABS, MHA-TP |
What are the non-treponemal tests? | RPR, VDRL |
What antibiotic should be used to treat patients with treponemal infection who are allergic to penicillin? | doxycycline |
What is the causative organism of Yaws? | T pallidum, subspecies pertenue |
What is the primary stage of yaws? | "mother yaw"- erythematous, infiltrated painless papule that occurs at the site of inoculation and heals spontaneously
-the lesion is rich in treponemes |
What is the secondary stage of yaws? | "daughter yaws"- smaller more widespread papules that usually occur at body orifices, such as the nose and mouth |
Where is yaws endemic? | tropical climates- Africa, Asia, South and Central America |
What is the final stage of yaws? | abscesses form that become necrotic and ulcerate, forming sinus tracts that heal with scarring and may form crippling deformities
-also may have periostitis, dactylitis, osteitis (saber shins) |
What is the causative organism of pinta? | Treponema carateum |
Where is pinta endemic? | Central and South America |
What is the primary lesion in pinta? | tiny macules or papules surrounded by an erythematous halo that develop into poorly defined erythematous plaques over months |
What are the secondary lesions in pinta? | "pintids"- small scaly papules that coalesce to form psoriasiform plaques that are initially red but then become slate-blue, brown or black (highly infectious) |
What are the tertiary lesions in pinta? | symmetric de-pigmented vitiligo-like lesions (not infectious) |
What stages of pinta are considered infectious? | primary and secondary (tertiary not considered infectious) |
Endemic syphilis is also known as? | Bejel |
What is the causative organism involved in endemic syphilis? | T. pallidum, subspecies endemicum |
Where is endemic syphilis found? | North Africa and Southeast Asia (warm climates) |
What is the primary lesion of endemic syphilis? | small inconspicuous papule or ulcer in the oropharynx or nipple of breastfeeding women (usually goes unnoticed) |
What is the secondary lesion of endemic syphilis? | -patches on mucous membranes
-split papules
-angular stomatitis
-condyloma lata
-osteoperiostitis which causes nocturnal bone pain |
What are the cutaneous manifestations of the tertiary stage of endemic syphilis? | gumma formation with gross mutilation of the skin, mucous membranes, muscle and cartilage |
How is leptospirosis transmitted? | contact of non-intact skin or mucous membranes with urine of infected animals (rodents) |
What are the two forms of leptospirosis? | 1) anticteric (>90%)
2) icteric (<10%)- more severe |
What are the cutaneous manifestations of leptospirosis? | variable- erythematous macules, papules, patches, or plaques and petechiae or purpura from vascular involvement |
What is the most common presentation of actinomycosis? | cervicofacial (lumpy jaw) caused by poor dental hygiene or a recent dental infection |
Where is actinomyces normal flora? | the human mouth, GI tract, and female genital tract |
What are the 3 forms of actinomycosis? | 1) cervicofacial (most common)
2) pulmonary (caused by aspiration)
3) GI |
What is the drug of choice for treatment of actinomycosis? | penicillin |