Seborrhoeic Dermatitis Clinical Overview
I. The "On-Call" Snapshot
Clinical Significance in Malaysia: This is one of the most common dermatological complaints you will see in Klinik Kesihatan, specialist clinics, and on the wards. It's often a "by-the-way" finding but causes significant patient distress. Importantly, severe or sudden-onset seborrhoeic dermatitis can be a cutaneous marker for underlying immunosuppression, particularly HIV.
High-Yield Definition: A chronic, relapsing, inflammatory skin disorder characterized by erythema and greasy scales in areas with a high density of sebaceous glands. (Source: UpToDate).
Clinical One-Liner: Think "dandruff of the scalp, face, and chest."
II. Etiology & Risk Factors
Etiology: The exact cause is not fully understood, but it is linked to a complex interplay between three factors:
Colonization by lipophilic yeasts of the genus Malassezia (specifically M. globosa and M. furfur), which are part of the normal skin flora.
Individual host susceptibility and an abnormal immune response to the yeast.
High sebaceous gland activity.
Risk Factors:
Age: Bimodal peaks in infancy ("cradle cap") and in adulthood (30s-60s).
Immunosuppression: HIV/AIDS (a classic association; prevalence up to 85% in patients with low CD4 counts), solid organ transplant recipients.
Neurological & Psychiatric Conditions: Parkinson's disease, stroke, epilepsy, major depression. The mechanism is thought to involve sebum overproduction due to autonomic dysfunction.
Environmental: Stress, fatigue, cold/dry weather can trigger flares.
III. Quick Pathophysiology
This is not primarily an infection. Malassezia metabolizes triglycerides in sebum, releasing pro-inflammatory free fatty acids like oleic acid. In susceptible individuals, these by-products trigger an inflammatory cascade, leading to hyperproliferation of the epidermis and the characteristic erythema and scaling you see on examination.
IV. Classification
Classification is straightforward and based on age of onset, which has direct implications for prognosis and management.
Infantile Seborrhoeic Dermatitis: Occurs in the first few months of life. Typically self-limiting. Presents as "cradle cap" (adherent, greasy scales on the scalp) but can also affect the face and flexures.
Adult Seborrhoeic Dermatitis: Occurs after puberty. Follows a chronic, relapsing-remitting course.
V. Clinical Assessment
🚩 Red Flags & Immediate Actions
Sudden, severe, or widespread eruption: Immediately consider testing for HIV. This presentation is highly suspicious for underlying immunosuppression.
Erythroderma (involvement of >90% body surface area): This is a dermatological emergency. Requires immediate admission for fluid/electrolyte management, thermoregulation, and exclusion of sepsis.
Failure to respond to first-line therapy: Re-evaluate the diagnosis and consider underlying systemic disease.
History
Key Diagnostic Clues: A relapsing history of "dandruff" or a red, flaky rash that worsens with stress. Pruritus is common but typically mild to moderate. Ask about location: scalp, eyebrows, behind the ears, nasolabial folds, and central chest are the classic sites.
Symptom Breakdown:
Common (>50%): Flaking scales (dandruff), mild to moderate pruritus, visible rash in seborrhoeic areas.
Less Common (10-50%): Burning sensation, blepharitis (eyelid margin inflammation).
Pertinent Negatives:
Absence of severe, intractable pruritus that wakes the patient from sleep (suggests atopic dermatitis or scabies).
Absence of thick, silvery, well-demarcated plaques on extensor surfaces (suggests psoriasis).
Absence of pustules, papules, and significant telangiectasia (suggests rosacea).
Physical Examination (OSCE Approach)
General Inspection: Patient is typically well and comfortable. Note distribution of the rash.
Vitals: Should be normal. Fever is not a feature unless secondarily infected.
Disease-Specific Examination (Dermatology):
Lesions: Look for ill-defined erythematous patches with overlying greasy, yellowish scales. In skin of colour, erythema may appear violaceous or hyperpigmented.
Distribution (Classic "Seborrhoeic Areas"):
Scalp: Diffuse scale (pityriasis capitis or "dandruff") is the mildest form. May have distinct erythematous plaques.
Face: Glabella (between eyebrows), eyebrows, nasolabial folds, malar areas. Blepharitis is common.
Ears: Retroauricular and in the conchal bowl.
Trunk: Presternal area ("petaloid" pattern), interscapular area.
Flexures: Axillae, inguinal folds, inframammary folds. Appears macerated and moist, often without prominent scale.
Pertinent Negatives:
No nail pitting or onycholysis (points away from psoriasis).
No Auspitz sign (pinpoint bleeding on removal of scale), which is characteristic of psoriasis.
Examination for Differentials:
Check extensor surfaces (elbows, knees) and sacrum for thick, silvery plaques (psoriasis).
Scrape a lesion margin gently for KOH microscopy if tinea is suspected (asymmetrical, active border).
Clinical Pearl: When you suspect seborrhoeic dermatitis, always check behind the ears and in the nasolabial folds. These are classic, often-overlooked sites that help confirm the diagnosis.
VI. Diagnostic Workflow
This is almost always a clinical diagnosis. Investigations are rarely required.
Differential Diagnosis:
Psoriasis (specifically "sebopsoriasis"):
Points For: Erythema and scale in similar locations (scalp, face).
Points Against: Psoriatic plaques are typically thicker, more well-demarcated, and have a silvery (not greasy-yellow) scale. Look for nail pitting and involvement of extensor surfaces.
How to Differentiate: Primarily clinical. A skin biopsy can confirm if diagnosis is uncertain.
Rosacea:
Points For: Affects the central face.
Points Against: Characterized by papules, pustules, telangiectasias, and flushing. Scaling is absent or minimal.
How to Differentiate: Absence of scale is the key differentiating feature.
Tinea (faciei or capitis):
Points For: Erythematous, scaling patch.
Points Against: Tinea is usually asymmetrical, has a raised, active border, and may show central clearing.
How to Differentiate: KOH microscopy of skin scrapings will show hyphae.
Investigations Plan:
Bedside: None.
First-Line Labs: Not indicated unless red flags are present. If presentation is severe or recalcitrant, an HIV test is mandatory.
Confirmatory / Gold Standard: A skin biopsy is the gold standard but reserved for atypical cases or those unresponsive to standard therapy.
VII. Staging & Severity Assessment
Severity is assessed clinically based on the extent of body surface area (BSA) involved, degree of erythema, and scaling. There is no universally adopted formal staging system. We generally describe it as mild, moderate, or severe.
Mild: Dandruff only, or minimal facial involvement.
Moderate: Obvious erythema and scaling on scalp and face.
Severe: Widespread involvement, significant inflammation, or refractory to topical therapy.
VIII. Management Plan
A. Principle of Management:
Reduce skin colonization by Malassezia.
Control inflammation.
Manage patient expectations: this is about control, not cure.
B. Immediate Stabilisation (The ABCDE Plan):
Not applicable for typical seborrhoeic dermatitis. This is a chronic outpatient condition. If the patient presents with erythroderma, manage as a dermatological emergency (refer to Dermatology, IV access, fluid resuscitation).
C. Definitive Treatment (The Ward Round Plan):
First-Line (Scalp):
Antifungal shampoo: Ketoconazole 2% shampoo (available in KKM formulary).
Instructions: Lather and leave on scalp for 5-10 minutes before rinsing, 2-3 times per week for 4 weeks, then reduce to once weekly for maintenance.
First-Line (Face, Trunk, Flexures):
Topical antifungal cream: Ketoconazole 2% cream applied OD or BD.
Low-potency topical steroid: Hydrocortisone 1% cream applied BD for short periods (1-2 weeks) to control inflammation. Use with caution on the face to avoid atrophy and perioral dermatitis.
Second-Line / Adjunctive Therapy:
Topical calcineurin inhibitors: Tacrolimus 0.1% ointment. Good steroid-sparing option for the face but may not be readily available in all settings.
Topical steroids (scalp): Betamethasone valerate scalp solution for severe pruritus or inflammation.
Severe / Refractory Disease (Specialist Management):
Oral antifungals (e.g., Itraconazole).
Phototherapy.
Short course of oral corticosteroids (rarely used).
D. Long-Term & Discharge Plan:
Educate the patient on the chronic, relapsing nature of the condition.
Advise on maintenance therapy (e.g., using ketoconazole shampoo once a week or every two weeks).
Discuss trigger avoidance (stress management, etc.).
Follow-up in primary care is usually sufficient.
IX. Complications
Psychosocial impact: Reduced self-esteem due to visible rash.
Secondary bacterial infection: Due to excoriation from scratching.
Side effects from treatment: Skin atrophy, telangiectasia from inappropriate long-term use of potent topical steroids on the face.
Erythroderma: Very rare but serious.
X. Prognosis
The prognosis for controlling the disease is excellent. However, it is a lifelong condition for most adults, with periods of flare and remission. Infantile seborrhoeic dermatitis usually resolves completely and does not predict adult disease.
XI. How to Present to Your Senior
Use the SBAR format.
S: "Dr, I'm calling about a 35-year-old gentleman in the clinic with a chronic, itchy facial rash."
B: "He has a 6-month history of a relapsing red, flaky rash over his eyebrows and nasolabial folds, consistent with seborrhoeic dermatitis. He has tried over-the-counter creams without improvement. No red flags."
A: "On examination, there are erythematous patches with fine, greasy scale in the typical seborrhoeic distribution. Vitals are stable. My primary diagnosis is adult seborrhoeic dermatitis. My main differential is sebopsoriasis, but there are no other features of psoriasis."
R: "My plan is to start him on ketoconazole 2% cream for the face and ketoconazole 2% shampoo for his scalp. I will also give a short course of hydrocortisone 1% cream for the facial inflammation. I would like your opinion on this plan."
XII. Summary & Further Reading
Top 3 Takeaways:
Diagnosis is clinical: look for greasy scale in seborrhoeic areas (scalp, face, chest).
Management targets both the Malassezia yeast (topical antifungals) and inflammation (low-potency topical steroids).
Sudden onset or severe disease warrants an HIV test.
Key Resources:
UpToDate: "Seborrheic dermatitis in adolescents and adults" - This is your primary resource.
Amboss: "Seborrheic dermatitis" - Excellent for a quick, structured review.
