# Clinical Cases: Common Dermatologic Conditions

## Case 1: Severe Nodulocystic Acne

### Patient Presentation
**Demographics:** 17-year-old male

**Chief Complaint:** Severe facial acne for 2 years, worsening despite treatment

**History of Present Illness:**
The patient has had progressive acne since age 15. Initial treatment with over-the-counter benzoyl peroxide and adapalene showed minimal improvement. He was subsequently treated with topical retinoids and oral doxycycline for 6 months with limited response. He now has painful nodules and cysts on his face, chest, and back. He is developing acne scars and reports significant emotional distress and social isolation.

**Past Medical History:**
- No significant medical history
- No known drug allergies

**Medications:**
- Previously tried: benzoyl peroxide, adapalene, clindamycin gel, doxycycline

**Physical Examination:**
- Face: Multiple open and closed comedones, inflammatory papules and pustules, deep nodules and cysts (some with purulent drainage)
- Scarring: Ice-pick and boxcar scars on cheeks
- Chest and back: Extensive nodules and cysts
- No signs of hidradenitis suppurativa

### Workup and Results

**Assessment:**
- Severe nodulocystic acne (Grade IV)
- Inadequate response to conventional therapy
- Candidate for isotretinoin

**Pre-Treatment Evaluation:**
- CBC: Normal
- Liver function tests: Normal
- Fasting lipid panel: Total cholesterol 175 mg/dL, triglycerides 120 mg/dL
- Pregnancy test: Not applicable (male patient)

### Clinical Image

![Nodulocystic Acne](case_01_image.jpg)

*Clinical photograph demonstrating severe nodulocystic acne with multiple inflammatory nodules, cysts, comedones, and early scarring on the face, characteristic of Grade IV acne vulgaris.*

### Diagnosis
**Severe Nodulocystic Acne (Grade IV) - Isotretinoin Candidate**

Acne pathogenesis involves four key factors:
1. Sebum overproduction
2. Follicular hyperkeratinization
3. Cutibacterium acnes colonization
4. Inflammation

### Discussion
This case illustrates severe acne requiring systemic treatment:

- **Four Pathogenic Factors**: The lecture describes the four main pathogenic factors in acne: sebum overproduction, follicular hyperkeratinization, C. acnes colonization, and inflammation. Severe nodulocystic acne involves all four factors in extreme form.

- **Isotretinoin Indication**: The lecture notes that isotretinoin is reserved for severe nodulocystic acne or acne unresponsive to conventional therapy. It is the only medication that addresses all four pathogenic factors.

- **iPLEDGE Program**: The lecture emphasizes that the iPLEDGE program is mandatory for isotretinoin due to its teratogenicity. While this male patient does not require pregnancy testing, he must still be registered in the program.

- **Benzoyl Peroxide Resistance**: The lecture highlights that benzoyl peroxide does not cause bacterial resistance, making it valuable as a combination therapy and helping explain why it should be combined with antibiotics.

### Treatment Plan
1. **Isotretinoin Therapy:**
   - Starting dose: 0.5 mg/kg/day
   - Target cumulative dose: 120-150 mg/kg
   - iPLEDGE enrollment and monthly registration

2. **Monitoring:**
   - Monthly liver function tests and lipid panels
   - Monitor for mood changes and depression
   - Pregnancy test monthly for female patients

3. **Supportive Care:**
   - Non-comedogenic moisturizer for dryness
   - Lip balm for cheilitis (expected side effect)
   - Avoid vitamin A supplements
   - No blood donation during treatment

4. **Duration:**
   - Typically 5-6 months depending on response
   - Course may be extended for cumulative dosing

### Teaching Points
1. Four pathogenic factors of acne: sebum, hyperkeratinization, C. acnes, inflammation
2. Isotretinoin addresses all four factors - only acne medication that does so
3. iPLEDGE program is mandatory for isotretinoin prescribing
4. Monitor pregnancy tests (females), LFTs, and lipids during treatment
5. Benzoyl peroxide does not cause bacterial resistance

---

## Case 2: Atopic Dermatitis with Eczema Herpeticum

### Patient Presentation
**Demographics:** 8-year-old female

**Chief Complaint:** Sudden worsening of eczema with fever and painful blisters

**History of Present Illness:**
The patient has had atopic dermatitis since infancy. Her eczema has been poorly controlled despite topical corticosteroids and moisturizers. Three days ago, she developed painful, grouped vesicles on her face and arms in areas of active eczema. She has a fever of 38.9C and appears ill. The lesions are spreading rapidly.

**Past Medical History:**
- Atopic dermatitis since age 6 months
- Allergic rhinitis
- Asthma

**Family History:**
- Mother has asthma and allergic rhinitis
- Brother has atopic dermatitis

**Physical Examination:**
- Temperature: 38.9C
- General: Ill-appearing
- Skin:
  - Widespread eczematous patches on flexural surfaces
  - Multiple punched-out vesicles and erosions on face and arms
  - Some vesicles with hemorrhagic crusting
  - Dennie-Morgan folds (infraorbital creases)
  - Lichenification in antecubital and popliteal fossae
- Lymph nodes: Tender cervical lymphadenopathy

### Workup and Results

**Laboratory Studies:**
- WBC: 14,200/mcL with left shift
- HSV PCR from vesicle fluid: Positive for HSV-1

**Clinical Assessment:**
- Eczema herpeticum (Kaposi varicelliform eruption) complicating atopic dermatitis

### Clinical Image

![Eczema Herpeticum](case_01_image.jpg)

*Clinical photograph showing eczema herpeticum with characteristic "punched-out" erosions and vesicles superimposed on eczematous skin, a dermatologic emergency in patients with atopic dermatitis.*

### Diagnosis
**Eczema Herpeticum (Kaposi Varicelliform Eruption)**

Complicating severe atopic dermatitis with:
- "Atopic triad" present (eczema, asthma, allergic rhinitis)
- Filaggrin-related barrier dysfunction
- HSV-1 dissemination in compromised skin

### Discussion
This case illustrates atopic dermatitis and its complications:

- **Atopic Triad**: The lecture describes the "atopic triad" of eczema, allergic rhinitis, and asthma. This patient demonstrates all three, along with a strong family history of atopy.

- **Filaggrin Mutations**: The lecture explains that filaggrin mutations lead to barrier dysfunction, a key factor in atopic dermatitis pathogenesis. This barrier defect allows easy entry of pathogens including HSV.

- **Distribution by Age**: The lecture notes that infants have face, scalp, and extensor involvement, while children and adults have flexural surface involvement (antecubital, popliteal). This patient shows the classic pediatric pattern.

- **Eczema Herpeticum**: The lecture identifies eczema herpeticum as a serious complication caused by herpes simplex virus. It is a dermatologic emergency requiring antiviral therapy.

### Treatment Plan
1. **Antiviral Therapy (Urgent):**
   - IV acyclovir 10 mg/kg every 8 hours
   - Continue until no new lesions for 48 hours
   - Then transition to oral valacyclovir to complete 10-14 day course

2. **Supportive Care:**
   - IV fluids for hydration
   - Pain management
   - Ophthalmology consultation (rule out ocular involvement)

3. **Wound Care:**
   - Gentle cleansing
   - Non-adherent dressings
   - Monitor for secondary bacterial infection

4. **Long-term Atopic Dermatitis Management:**
   - After HSV resolution, resume emollient therapy
   - Consider dupilumab (anti-IL-4/IL-13) for poorly controlled disease
   - Bleach baths to reduce S. aureus colonization

### Teaching Points
1. Atopic triad: Eczema, allergic rhinitis, asthma
2. Filaggrin mutations cause barrier dysfunction in atopic dermatitis
3. IL-4 and IL-13 are key cytokines (Th2 response) - targeted by dupilumab
4. Eczema herpeticum is an emergency requiring IV antiviral therapy
5. Dennie-Morgan folds are infraorbital creases associated with atopy

---

## Case 3: Psoriasis with Psoriatic Arthritis

### Patient Presentation
**Demographics:** 42-year-old male

**Chief Complaint:** Scaly skin plaques and new joint pain

**History of Present Illness:**
The patient has had psoriasis since his late 20s, primarily controlled with topical corticosteroids. Over the past 6 months, he has developed pain and swelling in multiple finger joints and his right knee. He reports morning stiffness lasting over an hour. He also noticed his fingernails have become pitted and are separating from the nail bed.

**Past Medical History:**
- Psoriasis vulgaris (plaque psoriasis) x 15 years
- Obesity (BMI 32)
- Hyperlipidemia

**Physical Examination:**
- Skin:
  - Well-demarcated erythematous plaques with silvery scale
  - Distribution: Elbows, knees, scalp, lower back
  - Koebner phenomenon (plaques at sites of old scars)
  - Auspitz sign present (pinpoint bleeding with scale removal)
- Nails: Pitting, onycholysis, oil spots
- Joints:
  - Dactylitis of right third finger ("sausage digit")
  - DIP joint swelling and tenderness
  - Right knee effusion
  - Enthesitis at Achilles insertion

### Workup and Results

**Laboratory Studies:**
- ESR: 42 mm/hr (elevated)
- CRP: 2.8 mg/dL (elevated)
- RF: Negative
- Anti-CCP: Negative
- HLA-B27: Positive

**X-rays:**
- Hands: Erosive changes at DIP joints
- "Pencil-in-cup" deformity of distal phalanx

**Skin Biopsy (prior):**
- Parakeratosis, acanthosis, elongated rete ridges
- Munro microabscesses

### Clinical Image

![Psoriasis](case_01_image.jpg)

*Clinical photograph demonstrating classic plaque psoriasis with well-demarcated erythematous plaques covered by thick silvery scale on the elbow, a common location for psoriatic lesions.*

### Diagnosis
**Psoriasis Vulgaris with Psoriatic Arthritis**

Features:
- Classic plaque psoriasis (80-90% of psoriasis cases)
- Psoriatic arthritis with DIP predominant pattern, dactylitis, and enthesitis
- Nail involvement (pitting, onycholysis)

### Discussion
This case illustrates psoriasis and psoriatic arthritis:

- **Th17/IL-17 Pathway**: The lecture identifies the IL-17 pathway as central to psoriasis pathogenesis. Th17 cells and IL-17/IL-23 drive keratinocyte hyperproliferation.

- **Accelerated Turnover**: The lecture notes that keratinocyte turnover is accelerated to 3-5 days (normal is 28 days), causing the characteristic thick scale.

- **Auspitz Sign**: The lecture describes pinpoint bleeding when scale is removed (Auspitz sign) as characteristic of psoriasis.

- **Psoriatic Arthritis**: The lecture states that approximately 30% of psoriasis patients develop psoriatic arthritis. Dactylitis ("sausage digit") is highly characteristic.

- **Nail Findings**: The lecture identifies nail pitting as characteristic of psoriasis.

### Treatment Plan
1. **For Joint Disease (Primary Concern):**
   - TNF-alpha inhibitor OR IL-17 inhibitor (secukinumab, ixekizumab)
   - Treats both skin and joints
   - NSAIDs for symptom relief

2. **For Skin Disease:**
   - Biologic therapy (same agent treats both)
   - Topical therapy for localized plaques (adjunct)
   - Narrowband UVB phototherapy if needed

3. **Comorbidity Management:**
   - Cardiovascular risk assessment (psoriasis increases CV risk)
   - Weight management (obesity worsens psoriasis)
   - Lipid management

4. **Monitoring:**
   - Joint exams every 3-6 months
   - PASI score for skin disease
   - Screen for TB before biologics

### Teaching Points
1. IL-17 and IL-23 are key cytokines in psoriasis (Th17 pathway)
2. Keratinocyte turnover accelerates to 3-5 days (normal 28 days)
3. Auspitz sign = pinpoint bleeding with scale removal
4. ~30% of psoriasis patients develop psoriatic arthritis
5. Dactylitis and nail pitting are characteristic findings

---

## Image Reference

For visual reference of common dermatologic conditions, see:
- Radiopaedia: [Psoriasis](https://radiopaedia.org/articles/psoriasis) - Clinical features
- Wikipedia: [Atopic dermatitis](https://en.wikipedia.org/wiki/Atopic_dermatitis) - Morphology
- Radiopaedia: [Acne vulgaris](https://radiopaedia.org/articles/acne-vulgaris) - Classification

---

## Learning Points

1. **Acne Pathogenesis**: Four factors - sebum, hyperkeratinization, C. acnes, inflammation; isotretinoin addresses all

2. **Isotretinoin Requirements**: iPLEDGE mandatory; monitor pregnancy tests, LFTs, lipids

3. **Atopic Dermatitis Features**: Atopic triad; filaggrin mutations; IL-4/IL-13 targeted by dupilumab

4. **Eczema Herpeticum**: Emergency requiring IV acyclovir

5. **Psoriasis/PsA**: IL-17 pathway; 30% develop arthritis; dactylitis and nail pitting characteristic