Paediatrics - Infection, immunity and allergy (1) Flashcards
Red flag symptoms for serious illness and urgent investigation
Fever of over 38 in <3 months Fever of over 39 if 3-6 months Colour - pale, mottled, blue Reduced consciousness, bulging fontanelle, neck stiffness, focal neurological signs, seizures Respiratory distress Bile-stained vomiting Severe dehydration/ shock
What form of antibody are transferred from mother to baby and for how long does this protection last?
IgG 6 months (but starts to reduce immediately)
4 investigations essential in a septic screen
and others that may be indicated (5)
- Blood culture
- FBC (inc. white cell count)
- CRP (acute phase reactant)
- Urine sample
Others: CXR, LP, Rapid antigen screen (blood/CSF/urine), meningococcal and pneumococcal PCR on CSF/blood, PCR for viruses in CSF (HSV/enterovirus)
Seriously unwell child presents to A&E, what antibiotic would be prescribed?
a) Child >3 months
b) Child<3months
a) Parenteral - 3rd generation cephalosporin (cefotaxime, ceftriaxone)
b) Parenteral Cefotaxime and ampicillin (if listeria infection suspected)
Can also give aciclovir if HS encephalitis suspected.
Common causes of a febrile child
- URTI
- Otitis media
- Serious bacterial infection if no focus (septicaemia, UTI)
- Tonsillitis
Most common cause of meningitis?
Viral infection
Two causes of non-infectious meningitis?
- Malignancy
2. Autoimmune disease
Percentage of patients in UK with bacterial meningitis that are under 16
80%
Pathophysiology of bacterial meningitis
Damage is due to host response to bacteraemia
- Release of inflam mediators and activated leucocytes with endothelial damage leads to cerebral oedema, ^ICP, decreased cerebral blood flow
- Inflammatory response below the meninges causes a vasculopathy resulting in a cerebral cortical infarction, fibrin deposits and resorption of CSF by arachnoid villi –> hydrocephalus
Most common bacteria causing meningitis in neonate - 3 months? (3)
- Group B strep
- Ecoli/other coliforms
- Listeria monocytogenes
Most common bacteria causing meningitis in 1 month - 6 years? (3)
- Neisseria meningitides
- Strep pneumoniae
- Haemophilus influenzae
Most common bacteria causing meningitis in >6 years?
- Neisseria meningitidis
2. Strep pneumonaie
Differentials for neck stiffness?
- Meningitis
- Tonsillitis
- Cervical lymphadenopathy
Signs of shock?
- Tachycardia
- Tachypnoea
- Prolonged cap refill
- Hypotension
If lumbar puncture contraindicated in child with suspected meningitis what is the management?
- Postpone LP until child stabilises
- Prescribe 3rd generation cephalosporin (cefotaxime/ceftriaxone)
- Bacteriological diagnosis with blood PCR or culture OR rapid antigen screen on blood and urine
- Obtain throat swab for viral and bacterial cultures
In suspected bacterial meningitis what would you prescribe alongside 3rd generation cef to minimise the risk of long-term complications?
Dexamethasone
Give 3 cerebral complications of meningitis?
- Hearing loss - inflammatory damage to cochlear hair cells
- Local vasculitis - cranial nerve palsies
- Local cerebral infarction - focal or multifocal seizures
- Subdural effusion - H.influenzae and pneumococcal menigitis associated
- Hydrocephalus - impaired resorption of CSF
- Cerebral abscess - confirmed by CT
All household contacts of a patient with meningococcal meningitis and H.influenzae meningitis are given what prophylaxis?
Rifampicin + meningococcal vaccine
What is the disadvantage of giving children antibiotics for a non-specific febrile illness?
If have early meningitis it may cause diagnostic problems
CSF will show increased white cells but culture may be negative
Rapid antigen screen (RAS) and PCR helpful
Causes of viral meningitis?
- Enteroviruses
- EBV
- Adenoviruses
- Mumps
Describe the two signs associated with neck stiffness in meningitis?
- Brudzinski sign - Flexion of neck with child supine causes flexion of knees and hips
- Kernig sign - Child lying supine and with hips and knees flexed, there is back pain on extension of the knee
Clinical features of meningitis in a child under 18 months?
- Fever
- Poor feeding
- Vomiting
- Irritability/lethargy/drowsiness/reduced consciousness
- Hypotonia
Late signs: Bulging fontanelle, neck stiffness, arched back (opisthotonus)
What should any child with a purpuric rash be given pre-hospital before being transferred?
IM benzylpenicillin
Clinical features of meningitis in a child over 18 months?
- Fever
- Photophobia
- Neck stiffness
- Brudzinski’s/Kernig’s
- Headache
- LOC
- Seizures
Can get papilloedema but rarely
Contraindications to LP in suspected meningitis
- Raised ICP (coma, high BP, low heart rate, pappiloedema)
- Cardiorespiratory instability
- Focal neurological signs
- Coagulopathy or thrombocytopenia
Investigations in suspected meningitis/encephalitis?
- FBC
- Blood glucose
- Coagulation screen/ CRP
- Culture of blood, throat swab, urine, stool for bacteria and viruses
- Rapid antigen test on CSF, urine or blood
- LP unless contraindicated
- PCR of blood and CSF
How would you confirm a diagnosis of viral meningitis?
Culture or PCR of CSF, stool, urine, throat swab and serology
Most common 3 clinical features in a child presenting with encephalitis?
- Fever
- Altered consciousness
- Seizures
Causes of encephalitis?
- Invasion of cerebrum by virus e.g. HSV
- Post-infectious encephalopathy (e.g. after chickenpox)
- Slow virus infection e.g. HIV/SSPE following measles
Most common organisms causing encephalitis in UK?
Enteroviruses, respiratory viruses or herpes viruses (HSV, varicella, HHV6)
Treatment of encephalitis?
High dose IV acyclovir
if HSV then prescribe for 3 weeks
Give the 3 signs of toxic shock syndrome?
- Fever >39
- Hypotension
- Diffuse erythematous, macular rash
Give other symptoms of TSS other than the 3 main signs of the syndrome (5)
- Mucositis (conjunctivitis, oral mucosa, genital mucosa)
- Vomiting/diarrhoea
- Liver impairment
- Clotting abnormalities e.g. thrombocytopenia
- Altered consciousness
Management of TSS
- Surgical debridement
2. 3rd generation cef + clindamycin
Two most common organisms causing necrotising fasciitis?
- Staphylococcus Aureus
2. Group A strep
Main form of meningococcal infection seen in UK?
Group B
What increases susceptibility to pneumococcal disease?
Hyposplenism (e.g. in sickle cell disease and nephrotic syndrome)
Main risk factor for impetigo?
Infants and young children with existing skin disease e.g. atopic eczema
Most common organisms causing impetigo?
Staph or strep
Where do impetigo lesions usually present?
Face, neck and hands
Describe the lesions in impetigo
Honey-coloured crusted lesions which emerge from erythematous macules.
Treatment for a) mild and b) severe impetigo
a) Topical antibiotic (mupirocin)
b) Flucloxacillin (narrow spectrum systemic)
Advice to parent of child with impetigo?
Shouldn’t be at school until lesions dry
Don’t touch as it will spread
Clinical features of periorbital cellulitis? (2)
- Fever
2. Erythema, tenderness and oedema of the eyelid (unilateral)
Causes of periorbital cellulitis?
a) H.influenzae in young, unimmunised children following trauma to the skin
b) Spread from paranasal sinus infection
c) Spread from dental abscess
What is the risk of periorbital cellulitis developing into?
Orbital cellulitis
Treatment of periorbital cellulitis?
IV antibiotics
Clinical features of orbital cellulitis?
- Proptosis
- Painful or limited ocular movement
- Reduced visual acuity
Investigations in suspected orbital cellulitis?
- CT to assess posterior spread of infection
2. LP to exclude meningitis
Organism commonly causing periorbital cellulitis?
Group A strep or staph aureus
What is scalded skin syndrome?
Staphylococcal toxin causes separation of the epidermal skin on gentle pressure. Seen in infants and young children
Also have fever, malaise, and purulent, crusting infection around eyes, nose, and mouth. Widespread erythema and tenderness of the skin.
Management of scalded skin syndrome? (3)
IV anti-staph antibiotic
Analgesia
Fluid monitoring
Treatment for HSV1 and 2
Aciclovir - DNA polymerase inhibitor
What is the most common for of primary HSV illness in children?
Gingivostomatitis
What is the cause of eczema herpeticum?
HSV - widespread vesicular lesions develop on eczematious skin and this can be complicated by secondary bacterial infection –> septicaemia
What virus causes chickenpox?
Varicella zoster
How is chickenpox spread?
Droplet
Normal incubation period of chicken pox?
10-23 days. Median 14
When is chickenpox infectious?
2 days before and up to 6 days after start of illness
Describe the symptoms of chickenpox?
Fever and itchy rash
Describe the rash in chickenpox
200-500 lesions
Start on the head and trunk
Progress to peripheries
Appear as crops of papules, vesicles, pustules and crusts with surrounding erythema
Appear at different times for up to 1 week
Complications of chickenpox?
Bacterial superinfection–>TSS/Nec fas
Aseptic meningitis or encephalitis (cerebellitis)
Pneumonitis/ DIC in immunocompromised
Which has a better prognosis, encephalitis due to varicella zoster virus or encephalitis as a result of HSV?
Varicella zoster.
Encephalitis as a result of HSV has a poor prognosis.
Treatment of chickenpox in an immunocompromised child?
What are you trying to prevent from happening?
Intravenous aciclovir/ valaciclovir
Attempting to prevent severe progressive disseminated disease which has a mortality of 20%
Treatment of chickenpox (primary varicella zoster infection) in adolescents/adults?
Oral valaciclovir
What would you prescribe in an immunocompromised child with deficient T-lymphocyte function following contact with chickenpox?
Human varicella zoster immunoglobulin (VZIG)
What virus causes shingles?
Herpes zoster
What causes shingles?
Reactivation of latent varicella zoster virus causing a vesicular eruption in the dermatomal distrubution of sensory nerves
Where is shingles most commonly seen on the body?
Thorax
Do children get neuralgic pain with shingles?
Generally no
Recurrent or multidermatomal shingles is generally associated with what?
Immunosuppression (e.g. HIV infection)
Maternal chickenpox shortly before or after delivery what would you give the fetus?
Human varicella zoster immunoglobulin (VZIG)
What virus causes glandular fever (infectious mononucleosis)?
Epstein-Barr virus
Which virus is associated with Burkitt’s lymphoma?
Epstein-Barr virus
What is Burkitt’s lymphoma?
High grade B-cell lymphoma (NHL) that is rapidly growing and aggressive. It is associated with EBV and chronic malaria or immunodeficiency.
Significantly more common in sub-saharan Africa
Often presents with swelling in maxilla or mandible, or rapidly enlarging non-tender lymph nodes in neck.
Transmission of EBV?
Oral contact
Syndrome seen in EBV
- Fever
- Malaise
- Tonsillopharyngitis - often severe, limiting oral ingestion of fluids and food and rarely, breathing
- Lymphadenopathy - cervical lymph nodes
Can also see: Petechaie on soft palate, splenomegaly (50%) hepatomegaly (10%) maculopapular rash (5%) and jaundice.
How do you diagnose glandular fever?
Atypical lymphocytes (numerous large T cells seen on blood film) Positive monospot test (heterophile antibody positive)
How long do glandular fever symptoms persist?
1-3 months
Which antibiotics should be avoided in children with glandular fever and why?
Amoxicillin and ampicillin can cause a florid maculopapular rash in children infected with EBV and should be avoided
Treatment of glandular fever?
Symptomatic
If airway compromised give corticosteroids
Penicillin if Group A strep on tonsils
Methods of transmission of CMV?
Saliva, genital secretions, breast milk
What syndrome is seen in CMV?
Mononucleosis syndrome (pharyngitis and lymphadenopathy) but not as prominent as EBV
How do you diagnose CMV?
Atypical lympthocytes on blood film (numerous large T-cells seen)
Negative monospot test (heterophile antibody-negative)
CMV infection is commonly seen in which 2 types of patients?
- Immunocompromised
2. Recipients of organ transplant (test by PCR)
Consequences of CMV infection (in immunocompromised patient)
- Retinitis
- Pneumonitis
- Bone marrow failure
- Encephalitis
- Hepatits
- Colitis
- Oesophagitis
Treatment of CMV?
Ganciclovir/ foscarnet
HHV-6 and 7 classically cause what?
Roseola infantum (exanthem subitum)
- high fever with malaise
- followed by a generalised macular rash
Erythema infectiosum or fifth disease is caused by what virus?
Parvovirus B19 (called slapped cheek syndrome)
When is erythema infectiosum/fifth disease most prevalent?
In the spring
Parvovirus B19 transmission route?
Respiratory secretions
Vertical transmission
Transfusion of contaminated blood products
What cells does parvovirus B19 invade?
Erythroblastoid red cell precursors of the bone marrow
Most common presentation of parvovirus B19?
Asymptomatic or erythema infectiosum
Describe symptoms of erythema infectiosum
- Fever, malaise, headache and myalgia
- Followed by a rash a week later on the face ‘slapped cheek’
- Progressing to a maculopapular rash on the trunk and limbs
What is an aplastic crisis?
The most serious consequence of Parvovirus B19 infection
- Occurs in children with chronic haemolytic anaemias where there is an increased rate of red cell turnover e.g. sickle cell/thalassemia and in immunodeficient children e.g. malignancy
The worst outcome of fetal parvovirus B19 infection?
Fetal hydrops and death
Give three examples of an enterovirus infection
- Coxsackie virus
- Echovirus
- Poliovirus
Transmission route of enterovirus?
Faecal-oral
Give three examples of diseases that are more severe in older children and adults than in younger children
- Chickenpox
- Parvovirus
- Measles
Clinical features of measles?
- Fever
- Maculopapular rash (spreads from behind the ears to the whole of the body) Maculopapular initially and then becomes blotchy)
- Koplik’s spots
- Conjunctivitis and coryza
- Cough
What are Koplik’s spots, when are they seen and at what stage in the disease?
White spots of the buccal mucosa seen in measles (pathognomonic)
Manifest two to three days before the rash
Give two serious complications of measles
- Encephalitis
- Subacute sclerosing panencephalitis (SSPE) - very rare appears 7 years after illness in 1/100,000 due to virus persisting in CNS
Treatment of measles?
- Symptomatic
- Isolate children who are admitted
- Antivirals (ribavirin)