Exanthemata

Question 1

What is exanthemata?

Answer 1

-To bloom/ break out
-Used to describe an acute onset, widespread skin rash
-Often associated with fever
=Usually in children
-Not necessarily infectious: allergens, toxins etc may trigger a similar phenomenon

Question 2

Examples of contemporary exanthemata

Answer 2

-Measles
-Scarlet fever
-Rubella
-Parvovirus B19 (slapped cheek/ 5th disease)
-Roseola infantum (6th disease)

Question 3

Causative organism of measles

Answer 3

-Measles morbillivirus
=Single-stranded, -ve sense RNA: Paramyxovirus family

Question 4

Causative organism of scarlet fever

Answer 4

-Streptococcus pyogenes, ONLY BACTERIA
=Streptococcus: Beta-haemolytic, Lancefield group A
=Necrotising fasciitis

Question 5

Causative organism of rubella

Answer 5

-Rubella virus
=Single-stranded, +ve sense RNA: Togavirus family

Question 6

Causative organism of parvovirus B19

Answer 6

-Parvovirus B19
=Single-stranded, DNA: Parvovirus family

Question 7

Causative organism of roseola infantum

Answer 7

-Human herpes virus 6
=Double-stranded DNA: Herpesvirus family

Question 8

Clinical course of measles

Answer 8

-Spread by droplets and contaminated surfaces
-Incubation period of 7-18 days
-Initial prodrome of fevers for 2-4 days
=With evolving coryza, conjunctivitis and Koplik’s spots
-Rash

Question 9

Appearance of measles rash

Answer 9

-Typically cranio-caudal spread (head to tail, upper back more affected than lower)
-Small macules/papules, becoming confluent (maculopapular rash)
-Blanching (initially)
-As it resolves there it can become non-blanching and the overlying skin may
desquamate

Question 10

Describe Koplik Spots

Answer 10

-Small, bluish-white,
firm lesions on the
buccal mucosa
-Useful in diagnosis
as precedes rash
by 24-48 hours
-However: present
only in a minority
(48%) of cases and
may be confused
for other forms of
oral ulcerations

Question 11

Clinical significance of measles

Answer 11

-Extremely high “attack rate” i.e. the chance of a non-immune, exposed person contracting measles is very high (15 mins in same room). R number 15

-Severe complications may occur with associated mortality
=Pulmonary measles
=Encephalitis, including subacute sclerosing panencephalitis (SSPE)

-Case fatality of around 1:1000 – higher in immunocompromised and malnourished
-Must be notified to Public Health

-Vaccine preventable
=MMR contains live vaccine, which is not suitable for immunocompromised patients

Question 12

Clinical course of scarlet fever

Answer 12

-Begins with pharyngeal infection with fever, cervical lymphadenopathy, and headache
-Florid rash appears 1-2 days after onset of sore
throat

Question 13

Appearance of scarlet fever rash

Answer 13

-Starts on face – circumoral sparing
-Blanching rash with elevations around hair follicles
-Capillary haemorrhage in skin folds – Pastia’s lines
-Strawberry tongue
-Rash is followed by desquamation

Question 14

Two immunologically mediated complications of scarlet fever

Answer 14

-Post-streptococcal glomerulonephritis (may follow pharyngeal or skin infection)
-Rheumatic fever

Question 15

Describe rheumatic fever

Answer 15

-Multi-system autoimmune disorder occurring 3 weeks after pharyngeal
streptococcal infection
-Pancarditis (peri-, myo- and endocarditis)
-Arthritis (large joints, migratory)

Question 16

Consequence of rheumatic fever

Answer 16

-May lead to valvular insufficiency
-Vulnerable to infective endocarditis in the future

Question 17

Clinical course of rubella

Answer 17

-Spread by droplets and contaminated surfaces
-Prodromal fever, and characteristic posterior auricular lymphadenopathy
-Rash appears after 2-3 days
=Typically macular
=May be itchy
=Lasts 2-3 days
=No desquamation or skin staining (cf. measles)
-Associated with small petechiae of the palate (Forchheimer’s Sign)

Question 18

What is the Forchheimer’s sign?

Answer 18

Posterior auricular lymphadenopathy

Question 19

Who is most affected by congenital rubella syndrome?

Answer 19

-The clinical significance of Rubella infection is not in children, but pregnant
women
-Risk depends on stage of pregnancy
=< 10 weeks 90%
=11-12 weeks 30%
=13-20 weeks <10%
=>20 weeks very low risk
-Features in the affected child may be transient, permanent or developmental

Question 20

Transient features of congenital rubella syndrome

Answer 20

-Hepatitis and jaundice, rash
-Thrombocytopenia
-Anaemia
-Lymphadenopathy

Question 21

Permanent features of congenital rubella syndrome

Answer 21

-Classic triad: Patent ductus arteriosus, cataracts and sensorineural deafness (occurs in c. 50% of affected babies)
-Other cardiac defects (e.g. PA stenosis), ophthalmic (e.g. retinopathy, corneal defects, glaucoma) or neurological (e.g. microcephaly)

Question 22

Developmental features of congenital rubella syndrome

Answer 22

-Increased risk of insulin dependent diabetes (20% by 35y)
-Thyroid disease
-Progressive hearing or visual loss

Question 23

Clinical course of parvovirus B19

Answer 23

-Fever then rash
=Initially on face followed 1-2 days later by generalised rash with characteristic lacy
appearance
-Can precipitate arthritis especially in adults
-Infect red cell precursor

Question 24

What does parvovirus B19 cause?

Answer 24

-Aplastic crisis in patients with pre-existing haemolytic anaemia (e.g. sickle cell)
-Chronic infection and anaemia in immunocompromised (e.g. HIV)
-Foetal anaemia (hydrops fetalis) in ~5% of maternal infections (risk highest in first trimester)

Question 25

Appearance of the parvovirus B19 rash

Answer 25

-Popular rash affecting cheeks (blanching, not itchy or painful)
-Maculopapular rash symmetrically affecting feet (and hands)- painful, significant oedema, non-blanching
-Papular Purpuric gloves and socks (rare manifestations)

Question 26

Describe Monkeypox

Answer 26

-Clinical syndrome caused by monkeypox virus
=Double stranded DNA virus of the poxviridae family
=Related to other pox viruses: vaccinia (smallpox), variola (used as smallpox vaccine)

-Historically only sporadic cases outside Africa, and limited transmission events
between humans
=Current outbreak: 35,000 cases, 6 fatalities (as of Aug 2022)
=Current epidemiology is mainly men who have sex with men
=Transmission can be abated by vaccination with smallpox vaccine