What are the differential diagnoses and initial management for linear erythematous papules in the pubic region?

Linear Red Bumps in the Pubic Area: Differential Diagnosis and Management

The most likely diagnoses for linear erythematous papules in the pubic region are folliculitis (especially if related to shaving), lichen sclerosus, or hidradenitis suppurativa, with folliculitis being the most common and benign cause that requires only conservative management, while lichen sclerosus demands prompt treatment with ultrapotent topical corticosteroids to prevent scarring and long-term complications.

Primary Differential Diagnoses

Folliculitis (Most Common)

• Folliculitis presents as papules and pustules primarily in the pubic hair region that are mildly tender and usually smaller than other inflammatory lesions 1
• This condition is particularly common with the increased popularity of shaving pubic hair 1
• The linear pattern may result from the direction of hair removal or razor trauma
• Patients should be counseled that shaving should be performed carefully with adequate lubrication to minimize trauma 1

Lichen Sclerosus

• Lichen sclerosus presents as porcelain-white papules and plaques with areas of ecchymosis, though early disease may show only small amounts of perimeatal or genital skin discoloration 1, 2
• The condition has a bimodal age distribution with peaks in prepubertal girls and postmenopausal women 2, 3
• The main symptom is pruritus (worse at night), but pain and dyspareunia occur specifically when erosions or fissures are present 1, 2, 3
• In females, it commonly affects the interlabial sulci, labia minora, clitoral hood, and perineal body in a figure-eight pattern 1
• In males, it typically involves the prepuce, coronal sulcus, and glans penis, potentially causing phimosis 1

Hidradenitis Suppurativa

• Hidradenitis suppurativa causes larger, tender, draining lesions that represent recurrent infection of apocrine glands 1
• These lesions are distinctly larger and more painful than folliculitis 1

Critical Diagnostic Approach

History Taking

• Document the duration, pattern of symptoms, and any periods of remission 2
• Distinguish between pruritus versus pain with erosions/fissures 2
• Assess for recent pubic hair shaving or grooming practices 1
• Inquire about associated symptoms: dysuria, dyspareunia, or changes in urinary stream 1

Physical Examination

• Inspect the pubic hair region noting Tanner stage and the presence of any lesions, including pubic lice, nits, folliculitis, and other inflammatory lesions 1
• Assess for signs of inflammation including redness or swelling, as well as any pigmentary changes, including hypopigmentation which can be seen in lichen sclerosus 1
• Evaluate for the characteristic porcelain-white appearance, ecchymosis, or areas of skin thinning suggestive of lichen sclerosus 1, 2

Laboratory and Diagnostic Testing

• STI testing, including gonorrhea and chlamydia nucleic acid amplification tests, is necessary, particularly if gland involvement is suspected 2, 3
• Viral culture for HSV and serologic testing for syphilis should be performed when ulcerations or papules are present 2, 3
• Biopsy of the affected area is the first-line diagnostic test to confirm lichen sclerosus and rule out squamous cell carcinoma when this diagnosis is suspected 2
• A biopsy is mandatory if there are atypical features, diagnostic uncertainty, or suspicion of neoplastic change 1

Management Algorithm

For Folliculitis (First-Line for Simple Cases)

• Conservative management with proper hygiene and cessation of shaving temporarily
• Warm compresses to affected areas
• Topical antibiotics if pustules are present
• Counsel patients on proper shaving technique with adequate lubrication to minimize trauma 1

For Confirmed or Suspected Lichen Sclerosus

• Ultrapotent topical corticosteroid clobetasol propionate ointment is the accepted first-line treatment for confirmed lichen sclerosus 2
• Apply clobetasol propionate once nightly for 4 weeks, then alternate nights for 4 weeks, and finally twice weekly for the final month 2
• For females: Clobetasol propionate 0.05% ointment on a regimen for 3 months (once a day for a month, alternative days for a month, twice weekly for a month), combined with a soap substitute and a barrier preparation 1
• For males: Clobetasol propionate 0.05% ointment once daily for 1-3 months with an emollient as a soap substitute and as a barrier preparation 1
• All people with lichen sclerosus should be managed by a healthcare professional experienced in treating the condition 1

For Hidradenitis Suppurativa

• Referral to dermatology for specialized management
• May require systemic antibiotics, immunosuppressive therapy, or surgical intervention

Critical Pitfalls to Avoid

• Do not dismiss ecchymosis in prepubertal girls as definitively indicating sexual abuse without considering lichen sclerosus 2, 3
• Always assess for STI pathogens when Bartholin or Skene gland infections are present 3
• Do not delay biopsy if lichen sclerosus is suspected and the diagnosis is uncertain, as early treatment prevents scarring 1, 2
• Long-term surveillance is mandatory due to the malignancy risk associated with lichen sclerosus 2
• Avoid forcing examination if the patient is not tolerating it; the examination should be stopped and tried again at a later time 1

When to Refer

• Consider referral to a specialist vulval clinic in all female patients (including children and young people) with lichen sclerosus not responding to a topical steroid, or if surgical management is being considered 1
• Refer males with phimosis that does not respond to ultrapotent topical steroids after 1-3 months to an experienced urologist for circumcision 1
• Any suspicion of malignancy requires immediate dermatology or surgical consultation 1, 2