Infection and Immunology Flashcards
Define abscess.
- a painful collection of pus, usually caused by bacterial infection
What are the presenting signs and symptoms of skin abscesses?
- Swollen, pus-filled lump under the surface of the skin with associated fever and chills
What are the presenting signs and symptoms of internal abscesses?
- Pain in the affected area (or referred pain)
- Swinging fevers
- Malaise
What are the appropriate investigations for abscesses?
o Ultrasound - can be useful in visualising an abscess
What is the appropriate treatment for abscesses?
o Some small skin abscesses may disappear by themselves
o Incision and Drainage
o Antibiotics
What is the most common cause of candidiasis?
- candida albicans
What are the risk factors for candidiasis?
Broad-spectrum antibiotics
Immunocompromise (e.g. HIV, corticosteroids)
Central venous lines
Cushing’s disease
Diabetes mellitus
GI tract surgery
What are the presenting signs and symptoms of oral candidiasis?
o curd-like white patches in the mouth, which can be removed easily revealing an underlying red base
- aka as oral thrush
What are the presenting signs and symptoms of oesophageal candidiasis?
Dysphagia
Pain on swallowing food or fluids
Name some AIDS-defining illnesses?
Candidiasis of the esophagus, bronchi, trachea, or lungs (but NOT the mouth)
Cervical cancer, invasive
Coccidioidomycosis, disseminated or extrapulmonary
Cryptococcosis, extrapulmonary
Cryptosporidiosis, chronic intestinal (greater than one month’s duration)
Cytomegalovirus disease or CMV (other than liver, spleen, or nodes)
Cytomegalovirus retinitis (with loss of vision)
Encephalopathy, HIV related
Herpes simplex: chronic ulcer(s) (more than 1 month in duration); or bronchitis, pneumonitis, or esophagitis
Histoplasmosis, disseminated or extrapulmonary
Isosporiasis, chronic intestinal (more than 1 month in duration)
Kaposi sarcoma
Lymphoma, Burkitt’s (or equivalent term)
Lymphoma, immunoblastic (or equivalent term)
Lymphoma, primary, of brain
Mycobacterium avium complex or M kansasii, disseminated or extrapulmonary
Mycobacterium tuberculosis, any site (pulmonary or extrapulmonary)
Mycobacterium, other species or unidentified species, disseminated or extrapulmonary
Pneumocystis pneumonia (PCP)
Pneumonia, recurrent
Progressive multifocal leukoencephalopathy
Salmonella septicemia, recurrent
Toxoplasmosis of brain
Wasting syndrome due to HIV
What are the presenting signs and symptoms of candidal skin infections?
Soreness and itching
Skin appearance can be variable
Red, moist skin area with ragged, peeling edge and possibly papules and pustules
What are the appropriate investigations for candidiasis?
o depends on the site
- oral candidiasis = swabs and cultures are not particularly useful because a lot of normal people have candida in their mouth
- oesophageal candidiasis = definitive diagnosis is by endoscopy
- invasive candidiasis = blood cultures required if candidaemia is possible
o therapeutic trials of antifungal (e.g. fluconazole) can help with diagnosis
Define cellulitis?
Acute non-purulent spreading infection of the subcutaneous tissue, causing overlying skin inflammation
What are the presenting symptoms of cellulitis?
o History of cut, scratch or injury
o Symptoms dependent on the location of the cellulitis
- periorbital cellulitis - painful swollen red skin around the eye
- orbital cellulitis - painful or limited eye movements, visual impairment
What are the signs of cellulitis on examination?
o Lesion - erythema, oedema, warm tender indistinct margins, pyrexia - may suggest systemic spread
o Periorbital - swollen eye lids, conjunctival infection
o Orbital Cellulitis - proptosis, impaired visual acuity and eye movements, test for RAPD, visual acuity and colour vision
What is the treatement for cellulitis?
o Medical = oral penicillins (e.g. flucloxacillin) or tetracyclines are effective
o Surgical = orbital decompression may be needed in orbital cellulitis (EMERGENCY)
What are the possible complications of cellulitis?
Sloughing of overlying skin
Orbital cellulitis - may cause permanent loss of vision, spread to the brain, abscess formation, meningitis, cavernous sinus thrombosis
Was viruses cause herpes?
- HSV1 = oral herpes
- HSV2 = genital herpes
What are the presenting symptoms of HSV1 infection?
o Pharyngitis, Gingivostomatitis (eating might be painful), Herpetic whitlow (abscess at the end of the finger caused by infection with HSV - it is very painful)
o THEN WHEN ON REACTIVATION = Prodrome of perioral tingling and burning, Vesicles/cold sores appear, Complete healing within 8-10 days
What are the presenting symptoms of HVS2?
Painful blisters and rash in the genital, perigenital and anal area
Dysuria
Fever
Malaise
What are the presenting symptoms of HSV2 encephalitis?
Usually caused by HSV1 so causes HSV1 type symptoms
What are the presenting symptoms of HSV2 keratoconjunctivitis?
Watering eyes
Photophobia
What are the signs of HVS1 infection on examination?
Tender cervical lymphadenopathy
Erythematous, oedematous pharynx
Oral ulcers filled with yellow slough (gingivostomatitis)
Herpetic whitlow
o Herpes Labialis (reactivation affecting the mouth) - Perioral vesicles/ulcers/crusting
What are the signs of HVS2 infection on examination?
Maculopapular rash
Vesicles
Ulcers
All of these are found on the external genitalia, anal margin and upper thighs
Inguinal lymphadenopathy
Pyrexia
What investigations should be carried out for herpes?
Diagnosis is usually CLINICAL
Vesicle fluid can be sampled and sent for electron microscopy, PCR
What are the 3 stages of HIV?
o Seroconversion - self-limiting, fever, night sweats, generalised lymphadenopathy, sore throat, oral ulcers, rash, myalgia, headache, encephalitis, diarrhoea
o Early/Asymptomatic - apparently well, persistent lymphadenopathy, progressive minor symptoms (e.g. rash, oral thrush, weight loss)
o AIDS - syndrome of secondary diseases resulting from immunodeficiency
What are the direct effects of HIV infection on the neurological system?
polyneuropathy
dementia
What are the direct effects of HIV infection on the lungs?
lymphocytic interstitial pneumonitis
What are the direct effects of HIV infection on the heart?
cardiomyopathy
myuocarditis
What are the direct effects of HIV infection on the haematological system?
anaemia
thrombocytopenia
What are the direct effects of HIV infection on the GIT?
anorexia
wasting
What are the direct effects of HIV infection on the eyes?
cotton wool spots
What are the appropriate investigations for HIV?
o HIV testing - HIV antibodies, PCR for viral RNA, CD4 count, viral load
o Pneumocystic pneumonia - CXR
o Cryptococcal meningitis - brain CT or MRI, LP
o CMV (colitis) - colonoscopy and biopsy
o Toxoplasmosis - brain CT or MRI
o Cryptosporidia - stool microscopy
Define infectious mononucleosis.
Clinical syndrome caused by primary EBV infection
AKA glandular fever
What are the presenting symtpms of infectious mononucleosis?
o Incubation period: 4-8 weeks
o Abrupt onset of symptoms = Sore throat, Fever, Fatigue, Headache, Malaise, Anorexia, Sweating, Abdominal pain
What are the signs of infectious mononucleosis on examination?
PYREXIA
Oedema and erythema of the pharynx
White/creamy exudate on the tonsils
Palatal petechiae
Cervical/generalised lymphadenopathy
Splenomegaly
Hepatomegaly
Jaundice (5-10%)
Widespread maculopapular rash (in patients who have received ampicillin)
What are the appropriate investigatiosn for infectious mononucleosis?
o Bloods - FBC = leucocytosis, LFTs = high AST/ALT
o Blood Film - lymphocytosis with atypical lymphocytes
o Heterophil Antibody Test - mixing blood of an EBV-positive human with animal blood will make the animal’s red cells aggregate and precipitate out of solution
o Throat swabs - exclude streptococcal tonsillitis
o IgM or IgG to EBV viral capsid antigen
o IgG against Epstein-Barr nuclear antigen (EBNA)
What is the treatment for infectious mononucleosis?
Bed rest
Paracetamol and NSAIDs - helps with fever, malaise
Corticosteroids in SEVERE cases
Advice - avoid contact sports for 2 weeks (because of risk of rupturing your spleen)
What are the possible complications of infectious mononucleosis?
Lethargy for several months
Respiratory - airway obstruction from oedematous pharynx, secondary bacterial throat infection, pneumonitis
Haematological - haemolytic or aplastic anaemia, thrombocytopenia
GI/Renal - splenic rupture, fulminant hepatitis, pancreatitis, mesenteric adenitis, renal failure
CNS - Guillain-Barre syndrome, encephalitis, viral meningitis
EBV-associated malignancy - Burkitt’s lymphoma (in sub-Saharan Africa), nasopharyngeal cancer, Hodgkin’s lymphoma
Define malaria.
Infection with protozoan Plasmodium
- Plasmodium falciparum = most serious
What populations have innate immunity to malaria?
Sickle cell trait
G6PD deficiency
Pyruvate kinase deficiency
Thalassemia
What are the presenting symptoms of malaria?
Feverish traveller (incubation period can be up to 1 year)
Symptoms are CYCLICAL/PAROXYSM:
High fever
Flu-like symptoms
Severe sweating
Shivering cold/rigors
What are the presenting symptoms of cerebral malaria?
Headache
Disorientation
Coma
What are the signs of malaria on examination?
Pyrexia
Anaemia (haemolytic)
Hepatosplenomegaly
What are the appropriate investigations for malaria?
o Thick/Thin Blood Films - thick for quantifying, thin for identifying type of malaria
o Bloods - FBC, U&Es, LFTs, ABG
o Urinalysis -check for blood or protein
Define varicella zoster.
Primary infection is called varicella (chickenpox). Reactivation of the dormant virus (found in dorsal root ganglia), causes zoster (shingles).
What are the presenting symptoms of chicken pox?
Prodromal malaise
Mild pyrexia
Sudden appearance of intensely itchy spreading rash mainly affecting face and trunk
Vesicles weep and crust over
New vesicles appear
Contagious from 48 hrs before the rash until after the vesicles have all crusted over (7-10 days)
What are the presenting symptoms of shingles?
May occur after a period of stress
Tingling/hyperaesthesia in a dermatomal distribution - dermatomal because the rash remains dormant in the dorsal root ganglia and reactivation makes the virus travel down the sensory axon to produce a dermatomal shingles rash
Painful skin lesions
Recovery: 10-14 days
What are the signs of chicken pox on examination?
Maculopapular rash
Areas of weeping and crusting
Skin excoriation (from scratching)
Mild pyrexia
What are the signs of shingles on examinations?
Vesicular maculopapular rash
Dermatomal distribution
Skin excoriation
What are the appropriate investigations of varicella zoster?
Usually CLINICAL diagnoses
Vesicle fluid may be sent for electron microscopy viral PCR (RARELY necessary)
Chicken pox in an adult with previous history of varicella infection may require HIV testing
What is the treatment plan for chicken pox?
Children - treat symptoms
Adults - consider acyclovir
What is the treatment of shingles?
Acyclovir, valaciclovir, famciclovir
What are the complications of chicken pox?
Secondary infection
Scarring
Pneumonia
Encephalitis
Congenital varicella syndrome
What are the complications of shingles?
Postherpetic neuralgia
Zoster ophthalmicus (rash in the ophthalmic division of the trigeminal nerve)
Ramsay-Hunt syndrome
Sacral zoster
Motor zoster
What is Ramsay-Hunt syndrome?
Reactivation of VZV in the geniculate ganglion causing zoster of the ear and facial nerve palsy. Vesicles may be seen behind the pinna of the ear or in the ear canal.
Define TB.
Infectious bacterial disease characterized by the growth of nodules (tubercles) in the tissues, especially the lungs.
What are the presenting symptoms of TB?
o Persistent cough.
o Haemoptysis
o Constant fatigue
o Weight loss
o Loss of appetite
o Fever
o Night sweats
o Tb outside the lungs = persistently swollen glands, abdominal pain, pain and loss of movement in an affected bone or joint, confusion, a persistent headache, fits (seizures)
What are the clinical signs of TB on examination?
o Dullness on percussion - Rales
o Vocal fremitus over affected area
What are the appropriate investigations for TB?
o Pulmonary TB = CXR and sputum cultures
o Extra-pulmonary TB = CT/MRI/USS, endoscopy, Bloods, Urine, aspiration/CSF samples for culture
o Latent TB = Mantoux test
