2. Infections - dermatological

Question 1

What are the features of purpura?

Answer 1

-Red-purple non-blanching discolouration of the skin caused by extravasation of RBCs
-Purpuric lesions <2mm in diameter = petechiae

Question 2

What can cause purpura?

Answer 2

-Viral (enterovirus)
-Sepsis (meningococcus)
-Thrombocytopenia
-Platelet / clotting disorders eg Von Willebrand’s
-Vasculitis eg Henoch-Schönlein purpura
-Trauma
-Drug reactions
-Vasomotor straining eg strenuous coughing, isometric exercise

Question 3

How is purpura managed?

Answer 3

-If patient is well and cause is benign –> reassure that rash will resolve spontaneously
-If cause is unclear:
–FBC
–Blood film
–Clotting screen
–Blood cultures
–BP
–Urinalysis + U+Es
-If possible sepsis –> BUFALO
-Stop any causative drugs
-Consider skin biopsy if diagnosis is unclear

Question 4

What happens if chicken pox is contracted in pregnancy?

Answer 4

-If exposed, find out if had before and check Ig
-If contracted in first 20w –> risk of foetal death or congenital varicella syndrome
-If contracted in second 20w –> baby is likely to contract herpes zoster in early life
-If contracted just before birth, neonate could acquire which is dangerous

Question 5

What causes chicken pox?

Answer 5

-Varicella coster virus
-Spread by respiratory droplets and direct contact with lesions
-Typical onset = 1-6 years

Question 6

What are the incubation and infectivity periods of chicken pox?

Answer 6

-Incubation = 10-21 days
-Infectivity = 4 days before rash - 5 days after

Question 7

How does chicken pox present?

Answer 7

-Rash typically starts on head and trunk –> whole body
-Red macules –> papules –> vesicles –> pustules –> crusting –> heal (within 2w)
-Headache
-Anorexia
-Sore throat
-Coryzal symptoms / cough / fever
-Itching

Question 8

How should chicken pox be managed?

Answer 8

-Itching –> short nails, calamine lotion, chlorphenamine >1y/o, cooling baths
-Paracetamol for fever
-School exclusion 5 days from start of skin eruption
-Aciclovir used if associated with:
–Severe disease
–Encephalitis
–Pneumonia
–Babies
–Immunocompromised patients

Question 9

What complications may arise from chicken pox?

Answer 9

-Invasive strep A infection –> necrotising fasciitis or TSS
-Rare –> purpura fulminans, cerebrovascular stroke, varicella encephalitis, life-threatening pneumonitis

Question 10

When does herpes zoster occur?

Answer 10

-Aka shingles
-Reactivation of latent infection may occur –> vesicular lesions in distribution of sensory nerves
-Very painful, more common in elderly / immunosuppressed / those who had primary infection in infancy

Question 11

When is neonatal conjunctivitis a concern?

Answer 11

-If swab shows gonococcal or chlamydial infection
GONOCOCCAL
-Should be suspected within first 48h of life if:
1. Purulent discharge
2. Swelling of the eyelids
-Treat with cephalosporin
-High risk of blindness
CHLAMYDIAL
-Usually presents around 7-10 days of life
-Ophthal review necessary

Question 12

What can cause childhood conjunctivitis?

Answer 12

BACTERIAL - Gram +ve cocci, H. influenza –> prurient discharge
VIRAL - adenovirus –> periauricular lymph nodes
ALLERGIC REACTION

Question 13

How is conjunctivitis managed?

Answer 13

-Usually self-limiting
-Topical chloramphenicol offered
-Don’t wear contact lenses or share towels

Question 14

How is allergic conjunctivitis managed?

Answer 14

-1st line = topical / systemic antihistamines
-2nd line = topical mast-cell stabilisers

Question 15

What are the incubation and infectivity periods of measles?

Answer 15

-Incubation = 10-14 days
-Infectivity = 4 days before rash starts - 4 days after

Question 16

What are the symptoms during the prodromal phase of measles?

Answer 16

Primarily occurs in the respiratory epithelium and nasopharynx
-Fever
-Coryza
-Cough
-Non-purulent conjunctivitis
-Koplik spots seen on buccal mucosa (white)
-Viraemia within 2-3 days

Question 17

How does the exanthematous phase of measles present?

Answer 17

-2nd viraemia occurs 5-7days after initial infection –> rash develops 7 days later
-Maculopapular rash
–Starts on face (behind the ears) –> whole body
–Becomes blotchy and confluent
–Lasts 6-8 days

Question 18

How does the exanthematous phase of measles present?

Answer 18

-2nd viraemia occurs 5-7days after initial infection –> rash develops 7 days later
-Maculopapular rash
–Starts on face (behind the ears) –> whole body
–Becomes blotchy and confluent
–Lasts 6-8 days
-Generalised lymphadenopathy
-Anorexia
-Diarrhoea
-Fever

Question 19

How is measles diagnosed?

Answer 19

-Clinical (Koplik’s spots)
-Buccal swab analysis
-Blood film (leukopenia, lymphophenia)
-LFTs (raised transaminase)

Question 20

How should you manage measles?

Answer 20

-Supportive treatment, ?abx if secondary bacterial infections
-A notifiable disease as highly contagious

Question 21

What causes periorbital cellulitis?

Answer 21

-Staph aureus or Hib
-May occur secondary to paranasal / dental abscesses or recent eyelid infection / insect bite
-Less serious than orbital cellulitis but can progress to it

Question 22

What systemic symptoms can preorbital cellulitis cause?

Answer 22

-Erythema
-Fever
-Tenderness over the affected area
-Oedema

Question 23

How should preorbital cellulitis be managed and what complications can evolve if it’s left untreated?

Answer 23

-Prompt IV abx for 5-7 days
Complications:
-Ocular proptosis
-Limited ocular movement
-Decreased visual acuity
Rare complications:
-Intracranial abscess formation
-Meningitis
-Cavernous sinus thrombosis

Question 24

What complications can evolve from measles?

Answer 24

-Acute OM
-LRTI
-Febrile convulsions
-Keratoconjunctivitis
-Encephalitis