Infectious Diseases Flashcards
What are the features of scarlet fever?
Occurs 24-48 hours after the sore throat
4Ss and 4Ps
S: Sore throat
S: Swollen tonsils
S: Strawberry tongue
S: Sandpaper rash
P: Perioral sparing
P: non-Painful
P: non-Pruritic
P: Peeling
>> Rash 24-48 hours after onset of fever/sore throat/strawberry tongue, occurring in the groin, axilla, neck and antecubital fossa
>> Generalized sandpaper rash with periorbital sparing within 24 hours
>> Look for Pastia’s lines (axillary rash)
>> Rash is nonpruritic and nonpainful, blanchable
>> Fades in 3-4 days
>> May be followed by desquamation
What is the specific management for Scarlet fever?
Penicillin for 10 days
What is the specific management for rheumatic fever?
- Penicillin for 10 days
- Prednisone if carditis is severe
- Secondary prophylaxis with daily penicillin
What is the Jones criteria for diagnosing rheumatic fever?
2 major or 1 major + 2 minor PLUS evidence of preceding streptococcal infection
>> History of scarlet fever
>> Group A streptococcal pharyngitis culture
>> Positive rapid Ag detection test
>> Raised ASOT
>> Raised anti-DNA-ase B
Major criteria:
- Migratory polyarthritis
- Carditis/new heart murmur
- Subcutaneous nodules
- Erythema marginatum
- Syndenham’s chorea
Minor criteria (PEACE)
- PR interval prolonged
- ESR raised
- Arthralgias
- CRP elevated
- Elevated temperature (fever)
What are the common presenting features of rubella?
STAR complex
- Sore throat
- Arthritis
- Rash
+ Low-grade fever and occipital nodes prodrome
Rash:
- 1-4 days after start of symptoms
- Starts on the face
- Spreads to neck and trunk
>> Excellent prognosis in acquired disease
>> Irreversible defects in congenital rubella syndrome
What are the presenting features of EBV?
Peak incidence: 15-19 years
Infants and young children: asymptomatic/mild disease
Adolescents:
- 2-3 days prodrome of malaise and anorexia
- Classical triad of:
>> Fever
>> Generalized non-tender lymphadenopathy
>> Exudative pharyngitis/tonsilitis
- Hepatosplenomegaly
- Periorbital edema
- Rash: more common after inappropriate treatment with B-lactam antibiotics due to misdx of strep throat
- Any “-itis”
What are the investigations that will aid the diagnosis of EBV infection?
- Monospot test
>> 85% sensitive in adults
>> 50% sensitive in children <4 years - EBV titres
- CBC and differentials: anemia, thrombocytopenia
- Blood smear: atypical lymphocytes and Downey cells
- Throat culture to rule out strep throat
What are the complications of EBV infection?
Short-term:
- Splenic rupture
- Airway obstruction
- Guillain-Barre syndrome/ADEM
- Hemophagocytic lymphohistiocytosis
Long-term (can be short-term)
- Burkitt’s lymphoma
- Nasopharyngiocarcinoma (NPC)
What is the management for EBV infection?
SUPPORTIVE
- Adequate rest
- Hydration
- Saline gargles and analgesics for sore throat
Acyclovir does NOT reduce duration of symptoms or result in earlier return to school or work.
What are the possible causes for fever in children?
Infection
- CNS
- Ears
- Eyes
- Upper and lower respiratory tracts
- Lung parenchyma
- Heart
- GI system
- Genitourinary systems: esp. UTI
- Skin - Connective/soft tissue
- Bones and joints
- Sepsis
Inflammatory/Autoimmune causes
- Kawasaki disease
- SLE
- JIA
- IBD
Neoplastic
- Leukemia
- Lymphoma
- Neuroblastoma
Iatrogenic
- Dehydration
- Drugs and toxins
- Post-immunization
What are the questions to ask when evaluating a febrile child?
- Does this child really have a fever?
- How old is this child?
- Are there any risk factors for infections?
- How ill is this child?
- Is there any rash?
- Is there a focus of infection?
What is this lesion? What is the management?
Impetigo
- Honey-crust lesion with fluid exudation
- Common organisms
>> Streptococcus pyogenes
>> Staphylococcus aureus
Management
- Avoid going to school
- Topical antibiotics: fucidic acid or mupirocin cream
- Systemic antibiotics if severe: cephalexin, erythromycin
- Eradicate nasal carriage by nasal antibiotic creams
What is the diagnosis? What are the common organisms? What are the complications?
Periorbital cellulitis
Common organisms
- Staphylococcus aureus
- Streptococcus pyogenes
- Hemophilus influenzae type B
Complications
- Orbital cellulitis
- Orbital abscess
- Meningitis
- Cavernous sinus thrombosis
What is the Centor criteria for Streptococcal A pharyngitis (for adults)?
- History of fever
- Tonsilar exudates
- Tender anterior cervical adenopathy
- Absence of cough
Age <15y: +1
Age >44y: -1
>> Score -1, 0, 1: antibiotics and throat culture not necessary
>> Score 2, 3: throat culture, and give antibiotics if throat culture positive
>> Score 4, 5: empirical antibiotics with follow-up throat culture
McIsaac Criteria: HOT LACE
HOT: fever >38C, Lymphadenopathy, Age (3-14 years), Cough absent, Exudative tonsils
What are the complications of Group A streptococcal pharyngitis?
- *Preventable by Antibiotics**
- AOM
- Mastoiditis
- Sinusitis
- Cervical adenitis
- Retropharyngeal/Peritonsillar abscess
- Sepsis
- *Immune-Mediated**
- Scarlet fever
- Acute rheumatic fever
- Post-streptococcal glomerulonephritis
- Reactive arthritis
- PANDAS (pediatric autoimmune neuropsychiatric disorder associated with Group A streptococcus)
Which immune-mediated sequelae of strep throat is preventable by antibiotics?
Rheumatic fever is preventable if antibiotics (penicillin V x 10 days) are given within 9 days of symptom onset. Post-streptococcal glomerulonephritis is NOT preventable.
>> Rheumatic fever: post-strep throat
>> Post-streptococcal glomerulonephritis: post-strep throat and post-skin infection
What are the complications of rheumatic fever?
- *Acute**
- Myocarditis
- Conduction system aberration
- Valvulitis
- Pericarditis
- *Chronic**
- Valvular heart disease (AR, MR)
- Infectious endocarditis +/- thromboembolic phenomenon
When does post-streptococcal glomerulonephritis occur?
1-3 weeks following the initial skin/throat GAS infecton
>> Peak at 4-8 years
>> Males > Females
How can the diagnosis of post-streptococcal glomerulonephritis be confirmed?
History/Presentation
- Asymptomatic
- Microscopic or macroscopic hematuria
- Other signs of nephritic syndrome
>> Proteinuria (<50mg/kg/day)
>> Hematuria
>> Azotemia
>> RBC casts
>> Oliguria
>> Hypertension
- *Investigations**
- Elevated ASOT
- Elevated anti-DNA-ase B levels
- Low C3 complement
- Confirm hematuria and proteinuria with urine dipstick
- Confirm azotemia with RFT
What is the management for post-streptococcal glomerulonephritis?
- Fluid and sodium restriction
- Loop diuretics
>> Edema
>> Hypertension - Dialysis may be required
- Penicillin V x 10 days if active GAS infection is present
95% children recover completely within 1-2 weeks
What is the definition of fever of known origin?
Daily or intermittent fevers for at least 2 consectuvei weeks of uncertain cause after careful history and physical and initial laboratory assessment
How does one assess a child presenting with fever?
History
- Characteristics of the fever
>> Duration
>> Height and pattern of fever
- Associated symptoms: headaches, dizziness, cough, SOB, HOV, rhinorrhea, wheezing/stridor, diarrhea, vomiting, change in stool character, oliguria, foul-smelling urine, change in urine colour and frequency, rash, unwilling to walk etc.
- TOCC: travel, cluster, contact
- Constitutional symptoms: feeding, irritability, ?playful, ?consolable, chills, rigor
- *Physical Examination**
- Toxic VS. Non-toxic
- Alertness and consciousness
- Vitals: temperature, BP, P, RR, SaO2, U/O — tachycardia, tachypnea, desaturation
- Growth chart
- Skin x Rash or foci of infection
- Systematic review: HEENT, chest, CVS, abdomen, genitalia, neuro, lymph nodes
Investigations
- For young children: full septic workup
>> Blood for CBC, d/c, C/ST, ESR, CRP, RLFT
>> Urine for urinalysis, C/ST
>> Stool for C/ST, microscopy
>> Sputum for C/ST, virology
>> NPA for C/ST, virology
>> CXR
NB: Febrile neonates should be considered high risk regardless of clinical presentation and laboratory findings — septic until proven otherwise
What is the disease? What is the causative organism?
Name the clinical features of the disease, the management and common complications.
5th Disease/Erythema Infectiosum
- Parvovirus B19
- Incubation 4-14 days
- Mode of transmission: respiratory secretions or infected blood
- 7-10 days of flu-like illness and fever
-
Rash
>> Onset 10-17 days after symptoms of flulike illness and fever
>> May be warm, pruritic and non-painful
>> Uniform, erythematous, maculopapular, “lacy” rash
>> “Slapped cheeks” – bilateral cheecks with circumoral pallor
>> May affect trunk and extremities - Glove-and-socks syndrome
- STAR complex (Sore Throat, Arthritis, Rash)
- Management is mainly supportive
- Complications
>> Aplastic crisis (as in post-viral EBV, HHV-6, HBV, HDV, HEV & HIV infections)
>> Rash may reappear under sunlight or after exercise months later
What is this disease? What is the causative organism? Name the clinical features.
Hand, Foot and Mouth Disease
- Coxsackie A (usually coxsackie A-16) virus
- Incubation period: 3-5 days
- Vesicles and pustules on an erythematous base in the hands, foots and mouth
- Vesicles on the POSTERIOR ORAL CAVITY (pharynx, tongue)
>> Management: supportive
>> Main complication: dehydration
This is measles. Describe the clinical features of the disease, and the mode of transmission.
Measles: Morbillivirus
- Incubation: 8-13 days
- Transmission: Airborne
- 3Cs Prodrome: Cough, Coryza, Conjunctivitis
- Koplik spots 1-2 days before rash onset
-
Rash:
>> Erythematous maculopapular rash that starts from the face down
>> Spares the palms and soles - Desquamation
Definitive diagnosis
- Positive serology for measles IgM
What is the management for measles?
Symptomatic treatment for the patient
- Notify Department of Health
- Respiratory isolation
For close contacts:
- Unimmunized
>> Measles vaccine within 72 hours of exposure
>> IgG within 6 days of exposure
What are the complications of measles?
- *Secondary Bacterial Infections**
- AOM
- Sinusitis
- Pneumonia
- Encephalitis
- *Other rare complications**
- Subacute sclerosing panencephalitis
- Myocarditis
- Pericarditis
- Glomerulonephritis
- Stevens-Johnson Syndrome
- Thrombocytopenia
This is roseola infantum. What is the causative organism? What are the clinical features and possible complications?
HHV-6
- High-grade fever
- Rash
>> Eppears once fever subsides
>> Blanchable, pink, maculopapular rash
>> Starts at neck and trunk; spreads to face and extremities (starts from middle!) - Irritability
- Poor feeding
- Lymphadenopathy
- Erythematous TM and pharynx
- Nagayama sign (see picture)
- *Complications**
- CNS: febrile seizures, aspetic meningitis
- Thrombocytopenia
- Post-viral aplastic anemia
What are the possible complications of varicella infection/chickenpox?
- *Skin**
- Bacterial superinfection (esp. Streptococcus pyogenes >> Scarlet fever)
- Necrotizing fasciitiis
- *CNS**
- Acute encephalitis
- Cerebellar ataxia
Systemic
- Hepatitis
- DIC
- Congenital varicella syndrome
>> Mental retardation/intellectual disability, microcephaly, hydrocephalus
>> Chorioretinitis, cataract
>> Cutnaeous scarring
>> Limb aplasia
>> Soft tissue calcification
What is the diagnosis? Describe the clinical appearance and the management plan.
Diaper Dermatitis: Irritant Contact Dermatitis
- Shiny red macules with NO FLEXURAL INVOLVEMENT >> sparing of skin folds
- Management
>> Eliminate direct skin contact with urine and feces
>> Allow periods of rest without a diaper
>> Frequent diaper changes
>> Topical barriers
:: Perolatum
:: Zinc oxide
:: Paste
>> Short-term low-potency topical corticosteroids in severe cases
What is the diagnosis? Describe the clinical features and management.
Diaper dermatitis: Candidal dermatitis
- Erythematous macerated papules/plaques with SHARP MARGINS, scaling and SATELLITE LESIONS
- Involves the intertriginous areas, i.e. involves skin folds
- Management
>> Examine for coexisting oral thrush
>> Topical antifungal agents: NYSTATIN
What is the diagnosis? Describe the lesion and possible management plan.
Infantile seborrheic dermatitis
- Yellow, greasy macules/plaques on erythema with scaling
- Cradle cap: yellow or white greasy scales on the forehead/face
- Starts from 2-3 weeks of life and usually clears in a few weeks
- Usually never occur
- Can occur in adults
- Management
>> Usually self-limiting
>> Short-term topical low-potency corticosteroids
What is the diagnosis? Describe the lesion and other common clinical features.
Atopic dermatitis
- Erythematous papules with crusting, oozing, excoriation and lichenification
- Location
>> Facial and extensor involvement during infancy
>> Flexural involvement in late childhood
>> Usually spares the diaper area - Chronic relapsing course with a personal or family history of atopy
>> Atopic dermatitis
>> Allergic rhinitis
>> Asthma - Prone to impetigo and are at risk for generalized cutaneous infection of HSV
Delineate the typical management plan for eczema.
Affects 10-20% of children
- *Non-medical Treatment**
- Non-soap cleansers and moisturizing soaps
- Fragrance-free and dye-free laundry detergent
- Food/Allergen avoidance
- Traditional Chinese Medicine
Enhance barrier function of the skin
- Regular application of moisturizers
- Emollients
>> Fragrance-free and dye-free
>> To hydrate skin
>> To reduce pruritis
>> Twice daily application is recommended even in the absence of symptoms
>> Apply especially after swimming or bathing
>> E.g. petrolium jelly, cetaphil cream
Anti-inflammatory therapy
- Topical steroids
>> Intermittent use to treat active, inflamed, palpable plaques
>> Discontinue once the areas are smooth
>> Side effects
:: Skin atrophy
:: Purpura
:: Striae
:: Steroid acne
:: Glaucoma when used around the eyes
- Topical immunomodulators
>> Calcineurin inhibitors: Tacrolimus, pimecrolimus
>> Side effects: skin burning, transient irritation
>> NOT indicated in children younger than 2 years
>> Pros over topical steroids
:: No skin atrophy
:: Safe for face and neck
:: Rapid sustained effect in controlling pruritis
- Systemic immunomodulators
>> Cyclosporin, azathioprine, tacrolimus and mycophenolate mofetil
- Phototherapy
- Antihistamines for pruritis
- Treat concomittant Staphylococcus infection: ?cloxacillin PO x 10 days
What is the diagnosis? What is the management plan?
Eczema Herpeticum
(Eczema + herpes infection)
>> THIS IS PAINFUL
- Admission
- Consult ophthalmologist
- Systemic antivirals (?acyclovir)
What is the diagnosis? Describe the lesion and management plan.
Molluscum Contagiosum
- Caused by poxviruses
- Spread by direct skin-to-skin contact
- Smooth, skin-coloured, 2-6mm, DOMED papules with CENTRAL UMBILICATION
- Predilection for skin folds (axillae and groin)
>> Warts tend to have a more jagged surface
>> Herpes simplex lesions are fluid-filled vesicles
>> Milia tend to be whiter in colour and more concentrated on hte face
Management
- Cantharidin (off-label but effective - extract from blister beetle)
- Cryotherapy
- Laser therapy
- Imiquimod 5% cream
What is the diagnosis? Describe the lesion and provide a typical management plan.
Tinea (corporis)
- Round erythematous plaques with CENTRAL CLEARING and a SCALY BORDER
Management
- Topical anti-fungal for skin (usually 1-6 weeks)
>> Terbinafine 1% cream
>> Clotrimazole 1% cream
>> Luliconazole 1% cream
- Systemic anti-fungal for nails/head (onychomycosis or tinea capitis)
>> Terbinafine
>> Itraconazole
>> Griseofulvin: reserved for severe cases
- Tinea pedis
>> Avoid humidity
>> Anti-fungal for at least 3 weeks
What is this lesion? Describe the clinical features and a possible management plan.
Scabies
(Sarcoptes scabies var. hominis)
- HIGHLY CONTAGIOUS AND PRURITIC
- Polymorphic lesions in web spaces/folds
- Diagnosis: clinical, skin scraping
Management
- Permethrin 5% cream for patient AND FAMILY
>> 2 applications, 1 week apart
>> Apply below the neck in older children and adults
>> Apply to the whole body for toddlers and infants
- Other insecticides
>> Lindane
>> Sulphur
>> Benzyl benzoate
What are the side effects of topical steroids?
- Skin atrophy
- Purpura
- Striae
- Steroid acne
- Glaucoma if used around the eye
What is the diagnosis? Describe the lesion and the common associations.
Erythema multiforme
- TARGET (classically bull’s-eye) lesions with damaged skin in the CENTRAL ZONE
- All lesions appear within 72 hours
- Fixed by at least 7 days
- Severe forms: Stevens-Johnson Syndrome (toxic epidermal necrolysis)
- *Common associations**
- Virus: HSV, Orf virus
- Bacteria: Mycoplasma
- Parasite: Histioplasma
- Drugs: NSAIDs, carbamazepine (1502), other anticonvulsants, allopurinol (5801), sulfonamides and penicillins
What kills in Stevens-Johnson syndrome?
Dehydration and infections
Morbidity:
- Ocular sequalae
- Scarring of skin
- Esophageal stricture
What is the diagnosis? Name the clinical features/diagnostic criteria and the possible management plan.
Stevens-Johnson Syndrome
- Variable skin rash and at least 2 mucosal lesions
- Usually preceded by a respiratory prodrome
- Mucosal lesions include:
>> Purulent conjunctivitis
>> Hemorrhagic erosions or necrosis over lips, peri-anus and urethral opening
Associations
- Drugs: NSAIDS, sulfonamides, penicillins, tetracyclines, anticonvulsants etc.
- Infections: HSV, Mycoplasma, Orf virus, EBV, TB, histioplasmosis etc.
>> Usually milder erythema multiforme (VS. drugs – SJS)
Management
- Hospitalization: burns unit or PICU where standard burn protocols are followed
- Fluid replacement
- Nutritional support
- Increased environmental temperature (28-30C)
- Regular culture of skin, blood and urine for infection
- Ophthalmology follow-up regularly
- Treat with acyclovir if HSV suspected
What is the diagnosis? What is the management?
Urticaria
- Can be very florid but usually disappears within 24 hours
- Skin is normal-looking after the rash recedes
- Second most common type of drug reaction
- Results from a release of histamine from mast cells in the dermis
Management
- Antihistmaines
- IV hydrocortisone for any accompanying angioedema
- IM adrenaline
>> 1:1000 = 1mg/mL
>> Adrenaline 0.05-0.5mL
Describe fixed drug eruptions.
Sharply demarcated erythematous oval patches on the skin or mucous membranes that reoccurs in the SAME location upon subsequent exposure to the drug – FIXED LOCATION – and thus the name “fixed drug eruptions”
Common drugs
- Antimicrobials: tetracycline, sulfonamides
- Anti-inflammatories
- Barbiturates
- Phenophthalein
What are the common drug reactions?
- Exanthematous eruptions
- Urticaria
- Fixed Drug Eruptions
- Erythema multiforme >> Stevens-Johnson Syndrome >> Toxic Epidermal Necrolysis
What is the diagnosis? How would you manage this patient?
Meningococcemia
- *Investigations**
- Blood culture
- Blood: CBC, clotting, RLFT, ESR, CRP
- CSF culture
- Skin lesion culture
- Urinalysis and C/ST
- *Treatment**
- Resuscitation
- Fluids
- Antibiotics
What are the differential diagnosis of a rash following a viral infection?
- Idiothrombocytopenic purpura
- Henoch-Scholein Purpura (HSP) — see picture
>> Vasculitis with RBC extravasation
>> Usually benign and self-limiting
>> Palpable purpura on buttocks and legs
>> Abdominal pain
>> Athralgia
>> Fever
>> Transient microscopic hematuria
How does one manage a case of diphtheria?
- Throat swab and culture to confirm
- Treatment is based on clinical suspicion
>> Diphtheria antitoxin
>> Penicillin G or erythromycin to halt further toxin production and prevent carrier
What are the possible complications of diphtheria?
5-10% mortality
- Airway obstruction
- Recurrent nerve palsy
- Diphtheritic peripheral neuritis
- Diphtheritic myocarditis
In whom does pertussis have the greatest incidence?
Children <1year (not fully immunized)
Adolescents (waning immunity)
What are the common causative organisms of preorbital and orbital cellulitis?
- *- Staphylococcus aureus
- Streptococcus pyogenes
- Streptococcus pneumoniae
- Moraxella catarrhalis**
- Hemophilus influenzae type B
ORBITAL CELLULITIS IS AN OCULAR AND MEDICAL EMERGENCY.
What are the cardinal signs of orbital involvement?
- Decreased visual acuity
- Ophthalmoplegia/diplopia
- Pain with extraocular eye movement
- Googly eyes
