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MODULE 5:
Integumentary System
PART 3 OF 7
Recurrent during fevers: tender red plaques, biopsied once — “dense neutrophilic infiltrate, no organisms.” Read as “atypical infection.” It was Sweet syndrome.
Slide 1 Transcript
PATIENT CHART
STINA
Grad student · recurrent fevers, pain & swelling since childhood
THIS PART
Ages 3-35
PRESENTING WITH
Variable skinThe body’s largest organ, providing protection and regulation. conditions
ACTION TAKEN
Dermatological evaluation
DIAGNOSIS
Sweet Syndrome
CHART CLUES
COLLECTED AS YOU GO
Post-Streptococcal Guttate Psoriasis
Concurrent Eczema + Sterile Pustulosis
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Put your money down: Pus with no germ — an infection, or something the swab can’t catch?
Certain fevers came with tender red plaques; one was finally biopsied, and the report found a dense crowd of neutrophils and not a single microbe — yet the note still read ‘atypical infection.’ Two quick fact-checks on how cellsThe basic structural and functional units of life. enter the skin; then the ask: was this an infection the swab missed — or sterile inflammation with a name?
Pick the answer you believe now. We’ll come back to it later!
A Biopsy That Was Almost a Confession
For years, certain fevers came with a skin signature: tender, juicy red plaques that erupted as her temperature climbed and faded as it broke. One was finally biopsied. The pathologist’s report was almost a confession — a dense crowd of neutrophils packed into the dermisThe thick inner layer of the skin that contains blood vessels, nerves, and connective tissue., and not a single microbe. The note still read “atypical infection,” and another antibiotic was prescribed for a rash that had no germ in it at all.
The Dermis Has Its Own Two Layers
A waterThe universal solvent essential for life. reservoir built on collagenA structural protein in the dermis that provides strength and elasticity. — the living scaffold beneath the epidermisThe outermost layer of the skin, made of stratified squamous epithelium..
Slide 2 Transcript
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Single Choice: What are the two layers of the dermis?
The Papillary Layer
Thin areolar tissue with sensors and patrols — and the vessels neutrophils exit into.
Slide 3 Transcript
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Drag the Words: Drop the features into the papillary layerhe upper layer of the dermis that contains blood vessels and sensory receptors..
How Neutrophils Pour Into the Skin
That picture has a name — Sweet syndrome, an acute febrile neutrophilic dermatosis — and it is a textbook IL-1β event. Danger signals (not pathogens) activate the inflammasome inside neutrophils; the cytokines that follow make dermal blood vessels sticky, and neutrophils pour out of the circulation into the skin by diapedesis. The fever and the rash share one thermostat: the same IL-1β that resets the hypothalamusA small but vital brain region controlling hormones, temperature, and autonomic functions. (the Intro to the Human Body module) is the signal calling neutrophils into the dermis. Stina’s “fever rash” is the case study’s whole thesis written in one biopsy.
The Reticular Layer
The deepAway from the surface of the body. 80% — dense, strong, collagen-packed.
Slide 4 Transcript
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Fill in the Blanks: Fill in what the reticular layerhe deeper portion of the dermis, containing collagen and elastin fibers for skin strength. is made of and does.
Aging in the Dermis
When collagen and water go, the surface shows it.
Slide 5 Transcript
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Mark the Words: Mark what changes in the aging dermis.
The Fever and the Rash, One Thermostat
The reason Stina’s fever and her rash always arrived together is that they run off one thermostat. The very same IL-1β that resets the hypothalamic set point and spikes her temperature (the fever mechanism from the Intro to the Human Body module) is the signal calling neutrophils into her dermis. One cytokine, two visible effects — a number on a thermometer and a plaque on the skin. Her “fever rash” is the whole thesis of this case study written out in a single biopsy: real, fierce, measurable inflammation, driven from within, with nothing to culture.
FINDING!
Sweet Syndrome — Acute Febrile Neutrophilic Dermatosis
Concrete sign: fever-linked tender red plaques, biopsied as a dense neutrophilic infiltrate with no organisms — and still charted as ‘atypical infection,’ with another needless antibiotic. That picture has a name: Sweet syndrome, an acute febrile neutrophilic dermatosis, and it is a textbook IL-1β/inflammasome event — danger signals (not pathogens) activate the inflammasome, dermal vessels turn sticky, and neutrophils pour into the skin by diapedesis. The same IL-1β that resets the fever thermostat calls neutrophils into the dermis.
Confirm or refute your bet: Pus with no germ — an infection, or something the swab can’t catch?
Having followed neutrophils out of the vessel and into the dermis by diapedesis, return to the bet. This is Sweet syndrome — an acute febrile neutrophilic dermatosis — a textbook IL-1β/inflammasome event, where the same cytokine that resets the fever thermostat calls neutrophils into the skin.
Slide 7 Transcript
NEXT PART
If inflamed vessels can fill the skin with neutrophils, what else can they do? Look at Stina’s legs — mottled, purple-netted, and red after a simple run — and the answer is written in the dermal circulationThe vascularization of the dermis of skin. Two capillary plexuses vascularize the dermis: subpapilla itself.
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All pages for Module 5 — The Integumentary System
5.0 Module Overview
5.1 The Rash Nobody Noticed
5.2 The Barrier Breaking Down
5.3 The Fever Rash
5.4 Red Feet & Mottled Shins
5.5 The Epidermal Conveyor Belt
5.6 Wounds That Won’t Heal
5.7 Inside the Skin’s Inflammation
5.8 Conclusion and Assessment
5.9 The evidence behind Stina’s skin
All Modules
- Anatomical Language, Membranes & Homeostasis
- Just Enough Chemistry
- The Cell & Its Transport
- Making Cells & Proteins
- The Integumentary System
- The Skeletal System
- The Muscular System
- Nervous Tissue & the Senses
- The Spinal Cord
- The Brain & the Blood–Brain Barrier
- The Autonomic Nervous System
- Special Senses (in developmentThe process of growth and differentiation.)
- The Endocrine System
- Blood
- The Heart
- Blood Vessels
- The Digestive System
- The Respiratory System
- The Urinary System
- Fluids, Electrolytes & Acid–Base Balance
- The Reproductive System
- The Immune System
List of terms
- skin
- cells
- dermis
- water
- collagen
- epidermis
- papillary layer
- hypothalamus
- deep
- reticular layer
- dermal circulation
- development