This document provides an overview of the differential diagnosis of various rashes by describing the characteristic features of common rash-causing conditions. It defines different types of rashes and lesions. Key conditions discussed include measles, chickenpox, rubella, erythema infectiosum, roseola infantum, scarlet fever, acute rheumatic fever, Kawasaki disease, mycoplasma infection, infectious mononucleosis, bacterial endocarditis, meningococcal infection, and herpes zoster. The document emphasizes gathering a thorough history and physical exam findings to differentiate between conditions and arrive at an accurate diagnosis of the underlying cause of a patient's rash.

1. DIFFERENTIAL DIAGNOSIS OF
RASHES

2. introduction
• Common problem.
• vary from simple one to an early sign of a life-
threatening condition .
• Mostly due to infection .

3. RASH
• A rash is a change of the human skin which
affects its color, appearance, or texture.
• A rash may be localized in one part of the
body, or affect all the skin. Rashes may cause
the skin to change color, itch, become warm,
bumpy, chapped, dry, cracked or blistered,
swell, and may be painful.

4. • The causes, and therefore treatments for rashes,
vary widely. Diagnosis must take into account
such things as the appearance of the rash, other
symptoms, what the patient may have been
exposed to, occupation, and occurrence in family
members. Rash can last 5 to 20 days, the
diagnosis may confirm any number of conditions.
The presence of a rash may aid diagnosis;
associated signs and symptoms are diagnostic of
certain diseases.

5. • For example, the rash in measles is
an erythematous, morbilliform, maculopapula
r rash that begins a few days after the fever
starts. It classically starts at the head, and
spreads downwards.

6. definitions
• Macule — Nonpalpable, circumscribed flat ,< 1 cm
• Papule — Palpable ,solid, elevated, < 1 cm
• Maculopapular -erythematous rash made up of both
macular and papular lesions.
• Purpura — Papular or macular nonblanching lesions
• Nodule — Deep-seated, roundish < 1.5 cm
• Plaque — A palpable elevated > 1
• Vesicle —elevated ,contains fluid , 1 cm
• Pustule —vesicle + pus
• Bulla —vesicle > 1 cm

7. history
• Characteristics of the lesions
• Distribution and progression of the rash
• Timing of the onset in relation to fever
• Change in morphology, such as papules to
vesicles or petechiae

8. History (important clues)
• Age of the patient
• Season of the year
• Travel history
• Exposures including to insects and ill contacts
• Medications
• Immunizations and history of childhood
illnesses

9. Physical examination
• Vital signs
• General appearance
• lymph nodes.
• mucous membranes, conjunctivae,
• ABDOMIN: Liver and spleen size
• CNS: Meningeal signs
• CVS: murmur

10. Measles (rubeola)
• maculopapular rash beginning in the head and
neck area and spreading centrifugally to the
trunk and extremities;
• fever, cough, coryza, and conjunctivitis
• high-dose vitamin A does seem to decrease
the morbidity and mortality
• Important sign: Koplik’s spots

12. Chickenpox
• is characterized by classic vesicular lesions on
an erythematous base that appear in crops .
• present in different stages from papules
through vesicles to crusting .
• Don’t underestimate few vesicles in era of
vaccination

14. Rubella
• not sick.
• prominent postauricular, posterior cervical,
and/or suboccipital adenopathy.
• Treatment : supportive
• 3 days measles

16. Rubella
• Clinical sign:
• Forchheimer’s sign.
• Petechiae on the hard palate

18. Erythema infectiosum (fifth disease)
• Erythema infectiosum (fifth disease) is due to
human parvovirus B19.
• rash with a "slapped cheeks" appearance
• Treatment: supportive .
• Pregnant and those with chronic hemolytic
anemia at high risk

20. Roseola infantum ( exanthem subitum)
• a human herpesvirus 6 or 7 infection.
• primarily seen in infants.
• is characterized by high fever for three to four
days followed by generalized maculopapular
rash that spreads from the trunk to the
extremities .
• Assosiated with febrile convulsion
• Fever then rash not at same time

22. Scarlet fever
• Caused by group A streptococcus (GAS)
infection.
• manifested by a coarse, sandpaper-like,
erythematous, blanching rash.
• This is accompanied by a strawberry tongue.
• Treatment: antibiotics

25. Acute rheumatic fever
• The classic dermatologic manifestations of
ARF are erythema marginatum
• transient macular lesions with central clearing
found on the extensor surfaces of the
proximal extremities and trunk.
• Less than 5 %

27. Kawasaki
• a disease of unknown etiology.
• is usually seen in children less than 5 years of age.
• addition to fever lasting >5 days,
• bilateral conjunctival injection.
• injected or fissured lips, injected pharynx or
'strawberry tongue' .
• erythema of the palms or soles, edema of the hands or
feet or generalized or periungual desquamation.
• Rash.
• cervical lymphadenopathy .

29. MYCOPLASMA
• Mild maculopapular rash.
• Eythema multiforme.
• Stevens –johnson syndrome.

33. Infectious mononucleosis
• present with fever, sweats, anorexia, nausea,
chills, sore throat, posterior cervical
lymphadenopathy, splenomegaly, and a
maculopapular rash.
• especially after the administration of ampicilin
• Gentle abdominal exam

36. Bactrial endocarditis
• mucocutaneous lesions include petechiae,
splinter hemorrhages, Janeway lesions, and
Osler's nodes
• Staph aurues is most common organisim

39. Meningococcal infection
• In addition to fever, headache, and nausea,
rash
• Early lesions may be macular, but rapidly
increasing numbers of petechial or purpuric
lesions can develop on the distal extremities
and trunk, usually sparing the palms and soles

42. Herpes zoster (shingles)
– Commonly affects a thoracic dermatome
– After a prodromal illness of pain and paresthesias,
erythematous macules and papules develop and
progress to vesicles within 24 hours
– The vesicles eventually crust and resolve
– Pain and sensory loss are the usual symptoms
– Motor weakness results when the viral activity
extends beyond the sensory root to involve the
motor root
– Cases of actual monoplegia due to varicella-zoster
virus (VZV) brachial plexus neuritis have been
reported

44. References
• Pictures – Derm atlas
• Oxford Handbook of Dermatology for primary
care ,Saxe ,Jessop
• Topics in Paediatrics ,Basson& Ginsberg

45. THANK YOU FOR YOUR KIND
ATTENTION