Download Skin Lesions DD And Investigations

Differential Diagnoses for Skin lesions
Emergency medicine Fellowship examination toolkit
1/16/2011
Amit Shetty
Bullous skin lesions
Causes
Solar/thermal injury
Contactants, including
 Rhus tree
 Grevillea (Robyn
Gordon type)
 Poison ivy
 Chemicals
Bullous impetigo
Herpes simplex infection
Varicella zoster infection
Pemphigus
Pemphigoid
Erythema multiforme
Porphyria, especially
 Porphyria cutanea tarda
 Porphyria variegata
SLE
Epidermolysis bullosa
Dermatitis herpetiformis
Appropriate Tests
Diagnosis based on history and physical examination, with
selected diagnostic imaging, endoscopy and pathology tests, as
indicated.
Patch testing is sometimes indicated. It should only be
performed by a specialist practitioner, as reactions may be
severe.
Pemphigus antibodies.
Pemphigoid antibodies.
Porphyrins - urine
Porphyrins, porphobilinogen - urine; porphyrins - faeces.
Molecular genetics, if available.
Transglutaminase antibodies.
See also Coeliac disease.
Staphylococcal scalded skin
syndrome
Toxic epidermal necrolysis
Graft versus host disease
Fixed drug reactions, especially
 Tetracycline
Vesicular skin lesions
Key Information
Viral infections
 Herpes simplex
 Varicella zoster
 Hand, foot and mouth
disease
 Molluscum contagiosum
Bacterial infection
 Streptococcus pyogenes

Clostridium perfringens
Appropriate Tests
Vesicle fluid for microscopy and bacterial culture, virus culture,
detection, if infection is a suspected cause.
Scraping of vesicle base for virus culture, detection.
Biopsy may be indicated.
Clinical diagnosis, testing not required.
Vesicles are usually a skin manifestation of severe underlying
sepsis with septicaemia. Blood culture.
Eczema
Trauma


Burns
Chemical damage
Adverse/fixed drug reactions
 Tetracycline
 Cotrimoxazole
 Topical applications
Dermatitis herpetiformis
Porphyria
Erythema multiforme
Causes/Associations
Appropriate Tests
Review clinical findings; FBC; CRP.
Skin biopsy with IF if diagnosis uncertain.
Stevens-Johnson syndrome is a term used to describe a severe
form of erythema multiforme with mucosal lesions and a poor
prognosis.
Idiopathic
Drug reactions, especially;
 Sulphonamides
 Barbiturates
 Phenytoin
Infections, especially;
 Herpes simplex
infection
 Mycoplasma infection
 Hepatitis B virus
infection
 Leprosy
Connective tissue diseases
Neoplasia
Anaphylaxis
Causes
Drugs, especially
Appropriate Tests
The acute episode is an emergency, which must always be
treated urgently.
Blood should be collected and stored for testing, including
complement components C3 and C4; tryptase to confirm
anaphylaxis, if indicated.
Subsequent investigation is required to establish cause:
skin prick allergen testing with suspected allergens or
allergen specific immunoglobulin E to detect specific IgE
to relevant agents.
See also angioedema, urticaria



Penicillins
NSAID including aspirin
General anaesthetic agents
Therapeutic/biological products,
especially
 Blood transfusion, including
Immunoglobulin A to exclude selective IgA deficiency.

o
Blood component
therapy
 Allergen desensitisation
 Insect stings
 Contrast agents
Food and other ingestants, especially
 Egg
 Milk
 Fish
 Peanuts
 Shellfish
 Other nuts
Contactants, especially
 Latex
 Diethyl-meta-toluamide
 Bacitracin/neomycin
Exercise-induced
Idiopathic
See Insect sting sensitivity.
See anaphylactoid reaction
See Latex allergy.
Present in insect repellants.
Angioedema
Causes
Drugs, especially
 ACE inhibitors
 Penicillins
Foods and other ingestants,
especially
 Preservatives
 Colouring agents
Insect stings
Contactants
Allergens
Idiopathic
C1 inhibitor deficiency
Hereditary angioedema
Acquired
Appropriate Tests
May be associated with Urticaria or Anaphylaxis.
Investigation should be appropriate to the clinical context:
FBC, CRP, C3, C4.
See Insect sting sensitivity.
C1 inhibitor immunological assay
Cellulitis
Key Information
Appropriate Tests
Pus or aspirate from edge of lesion - wound swab
microscopy and culture.
Blood culture if indicated.
Common pathogens
Streptococcus pyogenes
Anti-streptolysin O titre, anti-deoxyribonuclease B
antibodies.
Staphylococcus aureus
Clostridium perfringens
Haemophilus influenzae
Unusual pathogens
 Vibrio vulnificus
See Haemophilus influenzae infection.
Predisposing disorders include cirrhosis, diabetes mellitus,
haemochromatosis.
 Aeromonas hydrophila
Animal bites
 Pasteurella multocida
 Capnocytophaga canimorsus
Human bites
 Eikenella corrodens
See also Wound infection.
Erythema nodosum
Causes/Associations
Idiopathic
Streptococcus pyogenes
infection
Drug reactions, especially;
 Penicillins
 Sulphonamides
 Oral contraceptives
 Iodide
Sarcoidosis
Crohn's disease
Ulcerative colitis
Lymphoproliferative
disorders
Tuberculosis
Leprosy
Appropriate Tests
Review clinical findings.FBC, blood film. Skin biopsy (including
subcutaneous fat) if diagnosis uncertain.
Throat swab, wound swab – microscopy and culture (skin lesion);
anti-deoxyribonuclease B antibodies, anti-streptolysin O titre.
Purpura
Key Information
Thrombocytopenia
Vasculitis
'Senile purpura'



Elderly patient
Prolonged solar
exposure
Corticosteroid excess
Scurvy
Porphyria cutanea tarda
Appropriate Tests
Clinical assessment; FBC, blood film, platelet count.
Further investigation is unlikely to be productive unless there are
clinical features suggestive of vasculitis or there is a personal or
family history suggestive of a bleeding disorder.
The bleeding time and Hess test are neither sensitive nor specific
and are not appropriate.
Esp. Henoch-Schönleim purpura.
Usually seen in older, fair skinned patients who have had prolonged
solar exposure, with purpura typically on the forearms and dorsa of
hands.
See Cushing's syndrome.
Not a true form of purpura but may sometimes be confused with it.
The lesions are typical blistering and heal with scarring.
Wound infection
Frequent Pathogens
Trauma, including surgery
 Staphylococcus aureus
 Streptococcus pyogenes
 Bacteroides fragilis
With soil, faecal contamination
 Clostridium perfringens
With water contamination
 Aeromonas hydrophila
 Vibrio spp
With fish-handling
 Erysipelothrix
rhusiopathiae
With dog or cat bite
 Pasteurella multocida
Appropriate Tests
Minor wound infections may just require local drainage (eg,
removal of surgical suture) and do not require microbiological
testing.
Wound swab or pus - microscopy and culture for moderate or
severe infection, especially when there is spreading cellulitis or
symptoms and signs of systemic infection.
Aspiration of pus is preferable to a swab of pus or wound.
If aspiration or swab of pus, or wound swab, is not possible,
injection of 0.5-1.0 mL of saline followed by aspiration may
provide a suitable specimen (eg, from areas of cellulitis).

Capnocytophaga
canimorsus (dogs)
With human bite
 Eikenella corrodens
Bruising
Causes
Appropriate Tests
Bruising is usually due to trauma and investigation should only
be considered if the degree of bruising is disproportionate to
the trauma.
Exclude use of aspirin, other NSAID: Where indicated, initial full
blood count, PT/INR, APTT. If these are normal, and there is a
low prior probability of underlying bleeding diathesis, no
further investigation may be required.
Where von Willebrand disease is suspected, specific testing is
required. In selected cases, other coagulation studies, with
assays of specific coagulation factors and platelet function
studies may be indicated.
See Bleeding Disorders.
Unrecognised trauma, especially
 Child abuse
Simple easy bruising
Skin 'fragility', due to
 Elderly patients



Solar skin exposure
Cushing's syndrome,
including prolonged
corticosteroid therapy
Scurvy
Easy bruising is common, particularly in females.
Clinical diagnosis.
Easy and extensive superficial bruising ('senile purpura') is
common in the elderly and in those who have experienced
prolonged, excessive solar exposure - investigation is
inappropriate.
A
Anaphylaxis
Angioedema
2
3
B
Bruising
Bullous skin lesions
6
1
C
Cellulitis
4
E
Erythema multiforme
Erythema nodosum
2
4
P
Purpura
5
V
Vesicular skin lesions
1
W
Wound infection
5