What could be the cause of two bumps on the scalp of a female patient with no drainage that appeared over the last few days?

Scalp Bumps in a Female Patient: Differential Diagnosis

The two most likely diagnoses are folliculitis (inflammation of hair follicles) or sebaceous/epidermoid cysts, both of which are benign and common on the scalp. 1, 2, 3

Most Probable Diagnoses

Folliculitis

• Folliculitis presents as inflammatory papules and pustules in the hair-bearing regions of the scalp, often mildly tender and smaller than other inflammatory lesions. 1, 2
• Bacterial folliculitis caused by Staphylococcus aureus is the most common infectious cause of scalp bumps appearing over several days. 1, 2
• The scalp's pilosebaceous follicles are particularly susceptible to follicular inflammation, making this a frequent presentation in dermatological practice. 2

Sebaceous or Epidermoid Cysts

• Cystic lesions account for over 50% of all benign scalp lesions, including trichilemmal cysts (pilar cysts), epidermoid cysts, and sebaceous cysts. 3
• These present as firm, round bumps beneath the scalp surface without drainage unless secondarily infected. 3
• Inflamed epidermoid cysts may require incision and drainage if they become symptomatic, though Gram stain and culture are not routinely recommended for uncomplicated inflamed cysts. 1

Less Common but Important Considerations

Early Alopecia Areata

• Alopecia areata can initially present as scalp bumps or nodules before hair loss becomes apparent, characterized by perifollicular inflammation. 4
• Look for exclamation mark hairs (short broken hairs) around the bumps, which are pathognomonic for alopecia areata. 4
• Approximately 10% of alopecia areata patients also develop nail changes including pitting or ridging. 4

Hidradenitis Suppurativa (Scalp Variant)

• Dissecting cellulitis of the scalp represents HS of the scalp, characterized by perifollicular inflammatory nodules that can progress to interconnected draining tunnels. 1
• This condition is more common in women and presents with tender, suppurating nodules. 1

Clinical Approach

Key Physical Examination Features to Assess

• Examine for tenderness, warmth, and erythema surrounding the bumps, which suggest active folliculitis or abscess formation. 1
• Check for pustular drainage or central punctum, which indicates folliculitis or inflamed cyst. 1
• Assess for hair loss around the bumps or exclamation mark hairs, which would suggest alopecia areata. 4
• Palpate to determine if the bumps are superficial (folliculitis) or deeper subcutaneous nodules (cysts). 3

When to Culture

• Gram stain and culture are recommended for carbuncles and abscesses, but not for simple folliculitis or uncomplicated inflamed epidermoid cysts. 1
• Culture becomes important if there are recurrent lesions, systemic signs of infection (fever, tachycardia), or failure to respond to initial treatment. 1

When Further Workup is Needed

• If the bumps persist beyond 2-3 weeks or are associated with hair loss, consider dermoscopy to look for yellow dots and exclamation mark hairs suggestive of alopecia areata. 4
• Skin biopsy is reserved for atypical presentations, suspected early scarring alopecia, or when diagnosis remains uncertain after initial evaluation. 4, 2

Treatment Recommendations

For Folliculitis

• Most cases of simple folliculitis resolve spontaneously or with warm compresses and topical antibiotics. 1
• Systemic antibiotics active against S. aureus are indicated only if there are signs of systemic inflammatory response (fever >38°C, tachycardia >90 bpm) or extensive involvement. 1

For Inflamed Cysts

• Incision and drainage is the primary treatment for inflamed epidermoid cysts, carbuncles, and large furuncles. 1
• Simply covering the surgical site with a dry dressing is more effective than packing, which causes more pain without improving healing. 1

Critical Pitfalls to Avoid

• Do not assume all scalp bumps are benign without examining for hair loss, as early alopecia areata or scarring alopecia can present subtly. 4, 2
• Avoid prescribing systemic antibiotics for simple folliculitis without signs of systemic infection, as most cases are self-limited. 1
• Do not overlook the possibility of hidradenitis suppurativa in women with recurrent scalp nodules, as early recognition improves outcomes. 1