Little Red Riding Hood
A Dermatologic Journey
Children around the world know about Little Red Riding Hood’s famous journey to
Grandma’s house, but few know the real reason behind it.
For you see, Little Red Riding Hood was a sickly child, afflicted in particular with
skin problems. In fact, her parent’s can’t remember a single day in her life where
there wasn’t some type of rash or lesion on their poor daughter.
But as luck would have it, one day she awoke with completely clear skin (‘cause that
kind of thing happens in Fairy Tale Land). Her parents, normally afraid that their
Little Red Riding Hood may transmit something to sickly Grandma laying in bed,
immediately took this opportunity to send Little Red Riding Hood on a journey to
Grandma’s House...
This is the story of that journey.
Hopefully by the end you will be more familiar with problems of the skin, and
be able to:
• Identify the most common morphological presentations of skin lesion.
• Be able to fully describe any skin lesions based on:
• Shape,
• Arrangement,
• Color,
• Distribution and
• Morphology.
1. Shape
Before she could leave, Little Red Riding Hood had to put her toys away. Her favourite
was a block matching game from which she learned the shapes and arrangements
that her skin lesions could take:
Dome-Shaped
Pedunculated
Verrucous
Umbilicated
Flat-Topped
2. Arrangement
Linear
Discoid/Nummular
Grouped/Clustered
Annular
Targetoid
Serpiginous
3. Distribution
After her toys were neatly away, Little Red Riding Hood’s parents inspected her one
last time from head to toe for any signs of skin problems. They knew that certain skin
conditions follow specific distributions on the body, for example:
Acne Vulgaris
Atopic Dermatitis
Photosensitive Eruptions
Psoriasis
4: Color
With perfectly clear skin, Little Red Riding Hood was ready to leave and went to pick up
her cloak. She wore cloaks because they covered most of her body, and hid her skin
lesions from view.
There were many different color options, because skin lesions can take on many
different colors. Any given day Little Red Riding Hood would pick the one that would
hide most of her lesions best.
So little Riding Hood left her home, and the great expanse of
varied land she had to cross on the way to Grandma’s house
came into view. Undaunted, she set out on her way...
First she came to a vast flat grassland, as flat and smooth as a clear path
of skin. “What a beautiful field!” she exclaimed.
And it was, absolutely perfect save for a few discolored
patches of grass here and there.
The big patchy ones she called patches
and the little ones she called macules
for this is what the doctors called discoloured
areas that were flush with her own skin.
Macule: Flush, flat lesion that is implapable (can only see
due to color change). Usually less than 1.5cm in
diameter.
Example: Ephelides (freckles)
Patch: Large macule.
Example: Cafe-au-Lait Spot
Walking through the grasslands, she noticed that it was not all flat, as she saw
two hills up ahead. She named them after different sizes of bumps on her skin.
The bigger one, she called a:
The smaller, cuter one
she called a:
Papule
Nodule
Papule: Raised solid roundish lesion less than
1cm in diameter.
Example: Blue Nevus
Nodule: Large papule.
Example: Basal Cell Carcinoma
Making it past the hills, she came upon three different types of raised
landscape.
One was raised and flat on top just like the grasslands. A raised flat lesion on
the skin is what doctors called a plaque she thought.
Another was just like the first, except there seemed to be a lot more grass
growing over it, so much that some died and was flaking off. This looked to
her a lot like what doctors call a scale.
The third was an area of dried mud stuck onto the top of the normally
flat grassland. This reminded her of what doctors call a crust.
Plaque: Raised, flat palpable
lesion greater than 0.5cm in
diameter
Example: Pityriasis Rosea
Scale: Thickened flake of
stratum corneum (top layer
of the skin), easily detached.
Example: Psoriasis
Crust: Serum, blood
exudate firmly attached
to the skin. Occurs
when plasma exudes
through an eroded
epidermis. Not easily
detached
Example: Impetigo
Following the raised landscapes she saw a rough
jagged mountain arise from the surface of the land.
This reminded her of keratosis skin problems,
chunks of rough keratinocytes breaking the smooth
even surface of the skin.
Keratosis: Horn-like overgrowth of the skin
with involvement of keratin.
Example: Seborrheic Keratosis
Passing by the mountain, she saw a volcano, the crater filled with angry
boiling lava and rock.
She noticed it was quite similar to her pores, when filled with dead skin
and immune cells.
The docs called would call it an open comedone, the kids who
sometimes poked fun at her called them blackheads.
If the volcano opening was closed off, covered with a thin layer of
earth she thought, it would be much like a closed comedone, or
whitehead.
Comedo: Blocked pilosebaceous duct.
Example: Open Comedones (blackheads)
Example: Closed Comedones (whiteheads)
After carefully passing by the volcano Little Red Riding Hood was startled to
see an earthquake shaking an area of grassland! This was the weirdest
earthquake she’d even seen, for circles of land would randomly rise and fall
with no particular pattern.
This, she thought, looks exactly like the hives, or wheals as the doctors
called them, that present in this way on her skin when she has an allergy.
Wheal: Raised areas of dermal oedema.
Example: Urticaria (hives)
After the earth stopped moving, Red Riding Hood walked on. She was happy to see
smooth grasslands once again, but noticed that in some places the grass and soil was
either thin, completely gone, and even as deep as the bedrock in one place.
The thinning
areas were
like:
Atrophied skin
The deeper
areas of
eroded earth:
Erosions
With the
earth
completely
gone:
Ulcers
Atrophy: Thinning of the
epidermis, dermis, or both.
Example: Keloid
Erosion: Loss of the
epidermis.
Example: Tinea Pedis
Ulcer: Loss of the
epidermis and dermis.
Example: Leishmaniasis
Very close to Grandmother’s House, Red
Riding Hood’s foot started to ache.
She took off her sock and shoe to reveal:
A small blister which doctors call a:
A big blister which doctors call a:
Lichenification
Bull
A blister filled with pus which doctors call a:
And a callus which doctors call:
Vesicle
Pustule
Vesicle: Fluid filled lesion
less than 0.5cm in diameter.
Example: Varicella Zoster
Bull: Fluid filled lesion greater
than 0.5cm in diameter.
Example: Bullous Pemphigoid
Pustule: Pus filled vesicle.
Example: Insect bite.
Lichenification: Thickened skin with
exaggerated epidermal markings
caused by chronic scratching.
Example: Eczema
5. Morphology
Little Red Riding Hood finally made it
to Grandmother’s house.
Grandmother welcomed her warmly,
and Red Riding Hood told her about all
the sights she saw on the way.
See if you can recall the names with
Little Red Riding Hood:
Patch
Macule
Keratosis Comedone Wheal
Nodule
Papule
Plaque
Scale
Crust
Atrophy
Erosion
Bull
Vescicle
Ulcer
Pustule Lichenification
Little Red Riding Hood and her Grandma finally got a chance to spend some quality
time together (because Little Red Riding Hood took the long way to Grandma’s house,
the hunter had taken care of the wolf long before she reached her destination).
Especially important in Littler Red Riding Hood’s life, Grandma learned how to fully
name skin lesions. As you may remember, it includes 5 elements:
1. Shape
4. Distribution
2. Arrangement
5. Morphology
3. Color
For example:
One day after playing in the woods by her house, Little
Red Riding Hood came home with painful red circular
vesicles in a linear arrangement on her distal left
forearm.
What did she have? A reaction to poison ivy
Coming to the end of the journey with Little Red Riding Hood, let’s see if you can
apply the knowledge learned while on this trip by answering a couple of practice
questions:
Try to identify the following skin conditions. They’re tough, require a little prior knowledge
and are meant more than anything to illustrate the central importance of accurate and
detailed lesion description in diagnosis of dermatological problems:
Question 1:
You are rounding in a nursing home and encounter this
71 year old gentleman. He suffered from malaise,
headache and fever before the eruption. He also
seems to remember a tingling sensation in the area.
He is currently distressed and worries that it is "some
sort of cancer". What is the likely pathogen?
A: Varicella Zoster Virus (VZV)
B: Herpes Simplex Virus (HSV)
C: Measles Virus
D: Human Papillomavirus (HPV)
Question 2:
On a family medicine rotation, you see a 9 year old
boy with numerous small vesicular lesions on
erythematous bases. The lesions are all in different
stages of evolution and appear over the trunk and
face. The most likely diagnosis is:
A: molluscum contagiosum
B: chickenpox
C: impetigo
D: erysipelas
The End
Credits:
Author: Jakub Sawicki
Special thanks to Sheila Pinchin from the Office of Health Sciences Education and Amy
Allcock from MEdTech for their invaluable help in putting this module together.
Practice Questions courtesy of Nicole Hawkins from Queen’s Meds 2009. Many more
helpful resources and questions available at DermStudent.com