Clinical overview
Pigmentary disorders of the vulva are common but under-taught. They are clinically important not because they are dangerous (most are not) but because: (1) they cause significant distress and stigma when visible; (2) they can be mistaken for sinister diagnoses such as VIN or melanoma if the registrar does not recognise their pathology; (3) some require biopsy to exclude malignancy. This chapter describes the pathological features of the main pigmentary disorders of the vulva and adjacent skin — vitiligo, albinism, post-inflammatory hyperpigmentation, lentigo, melanotic macules, melanoma, and the related entity of intertrigo (an inflammatory dermatosis with secondary pigmentary changes).
Core knowledge
Vitiligo
Vitiligo destroys melanocytes, while albinism preserves melanocytes but reduces melanin production.
Pathology:
- Autoimmune destruction of melanocytes in the epidermal basal layer.
- Complete absence of melanocytes in fully developed lesions.
- T-cell mediated; associated with other autoimmune diseases (thyroid, type 1 diabetes, alopecia areata).
- Wood's lamp shows enhanced demarcation.
Clinical correlate:
- Sharply demarcated milky-white patches with no pigment.
- Symmetric, often peri-orificial (vulva, mouth, eyes, axilla, perianal).
- Asymptomatic; no scaling, no itch.
- May koebnerise — develop at sites of trauma.
Management: topical steroids or calcineurin inhibitors; phototherapy (narrowband UVB) where access permits; cosmetic camouflage; psychological support.
Albinism (oculocutaneous)
Pathology:
- Genetic disorder of melanin synthesis (TYR, OCA1; OCA2 mutation in southern African populations highest prevalence globally — ~1:3,900 in some communities).
- Melanocytes present but produce little or no melanin.
- Affects skin, hair, eyes.
Clinical correlate:
- Diffuse hypopigmentation of skin, hair, and irides.
- Increased susceptibility to UV damage and squamous cell carcinoma (substantial issue in South Africa).
- Vulval skin is similarly hypopigmented; standard gynaecological care plus sun protection advice for non-vulval skin.
Management: dermatological surveillance for skin cancers; sun protection; supportive social services.
Post-inflammatory hyperpigmentation (PIH)
Pathology:
- Increased melanin deposition in epidermis and/or dermis following inflammation.
- Melanophages (melanin-laden macrophages) in dermis = dermal PIH (more persistent).
- Common after lichen planus, lichen sclerosus, candidiasis, trauma.
Clinical correlate:
- Dark patches at sites of previous inflammation.
- More pronounced in patients with darker skin (Fitzpatrick IV–VI).
- May persist months to years.
Management: treat underlying inflammation; reassurance; topical depigmenting agents (limited use on vulval skin); sun protection where exposed.
Lentigo
Pathology:
- Localised increase in epidermal basal melanocytes.
- Sharply demarcated, uniformly pigmented macule.
- Histology: increased melanocytes along the rete ridges without nesting.
Clinical correlate:
- Single or multiple flat brown macules on vulva.
- Stable; not pre-malignant.
- Biopsy to differentiate from lentigo maligna (melanoma in situ) if clinically suspicious — irregular border, asymmetry, larger size, change over time.
Vulval melanotic macule (vulval melanosis)
Pathology:
- Hyperpigmentation due to increased melanin in basal keratinocytes without increased melanocyte number.
- Histology: basal hyperpigmentation; no atypia.
Clinical correlate:
- Single or multiple flat, well-demarcated brown patches.
- Asymptomatic.
- Can mimic melanoma — biopsy if atypical features.
Vulval melanoma
Pathology:
- Malignant melanocytic neoplasm.
- May arise de novo or from existing naevus.
- Subtypes: superficial spreading, nodular, lentiginous, amelanotic.
- Histology: atypical melanocytes with nesting, pagetoid spread, dermal invasion.
- Staging by Breslow thickness and ulceration; sentinel lymph node biopsy for primaries ≥1 mm.
Clinical correlate:
- Pigmented lesion with ABCDE features: asymmetry, irregular border, colour variation, diameter >6 mm, evolution.
- May present as ulcerated lesion (advanced).
- Vulval melanoma has poorer prognosis than cutaneous melanoma elsewhere due to delayed diagnosis.
See melanoma for full coverage.
Intertrigo
Pathology:
- Inflammatory dermatosis in skin folds due to friction, moisture, and microbial overgrowth (Candida, bacteria).
- Acute: erythema, maceration, occasionally erosions.
- Chronic: lichenification, hyperpigmentation.
Clinical correlate:
- Inguinal folds, intergluteal fold, sub-mammary, inframammary areas commonly affected.
- Vulval involvement causes itch, burning, dyspareunia.
- Risk factors: obesity, diabetes, hyperhidrosis, immobility.
Management: keep area dry, topical antifungal/antibacterial as appropriate, low-potency topical steroid for short course, address underlying factors (weight, glycaemic control).
Acanthosis nigricans
Pathology:
- Velvety hyperpigmented thickened skin in folds.
- Associated with insulin resistance (PCOS, type 2 diabetes), obesity; occasionally with internal malignancy.
- Histology: papillomatosis, hyperkeratosis; not increased melanin per se but appears darker due to architectural change.
Clinical correlate:
- Posterior neck, axillae, inguinal folds, vulval skin folds.
- Marker of metabolic disease.
Management: treat underlying insulin resistance (weight loss, metformin); topical retinoids; cosmetic.
Assessment
Examination
- Inspect with good lighting; document distribution.
- Wood's lamp where available (vitiligo enhances).
- Palpate for thickening, ulceration.
- Inspect mucosal surfaces — vitiligo may not affect mucosa; melanoma can.
Investigations
- Biopsy any pigmented lesion with atypical features (ABCDE), persistent ulceration, or change over time.
- Thyroid function in suspected vitiligo (autoimmune association).
- Diabetes screening if acanthosis nigricans.
- Diabetes/obesity screening if intertrigo.
Management
- Treat each condition as outlined above.
- Refer to dermatology for diagnostic uncertainty or atypical presentations.
- Refer to gynaecologic oncology for any concern of vulval melanoma.
Red flags / pitfalls
- Missing melanoma — biopsy any atypical pigmented lesion.
- Calling lichen sclerosus "vitiligo" — they are distinct (LS has texture change, atrophy; vitiligo is purely pigment loss).
- Forgetting that albinism elevates skin cancer risk — comprehensive skin surveillance.
- Missing acanthosis nigricans → metabolic syndrome screen.
- Anchoring on candida in intertrigo without addressing weight and friction.
Evidence anchors
- BSSVD (British Society for the Study of Vulval Disease) Guidelines for management of vulval pigmented lesions.
- ISSVD classification of vulval dermatoses.
- South African Albinism Society resources; National Department of Health albinism support.
- WHO and dermatology textbooks on vitiligo (Vitiligo European Task Force).
- Spechler SJ, et al. Cutaneous Pigmented Lesions: Diagnosis and Management.
- AAD (American Academy of Dermatology) Guidelines on Melanoma Diagnosis.