Fiona M. Lewis Increased vulval pigmentation presents a clinical diagnostic challenge, and is often impossible to diagnose accurately without histology, even with the aid of dermoscopy. Vascular lesions can often look very dark and cause diagnostic confusion. The differential diagnosis with any pigmented lesion or more diffuse pigmented areas must include melanoma, and so lesions should be biopsied and then subjected to good clinicopathological correlation. Melanin is the major determinant of skin colour, and there is considerable variation in the normal pigmentation of the keratinised vulval skin depending on ethnicity, age, and hormonal status (see Chapter 2). Alteration in pigmentation can be related to endocrine factors, such as Addison’s disease, and exposure to some drugs. These appearances are usually symmetrical, and there may be similar lesions on the skin or other mucosal surfaces. Pigmentation due to haemosiderin deposition tends to have a reddish‐brown tinge, rather than the brown or bluish‐black colour found with melanin. It occurs as a result of extravasation of blood and is a feature of lichen planus and Zoon’s vulvitis, urethral caruncles, and prolapsed tissue of cervical, vaginal, or rectal origin. Various techniques are available to help with the diagnosis of pigmented lesions, but histology remains the gold standard. This chapter deals with disorders leading to hyper‐ and hypopigmentation. Isolated pigmented melanocytic lesions are discussed in Chapter 38. Post‐inflammatory hyperpigmentation is frequently found on the vulva. It is particularly common after lichen sclerosus, lichen planus (Figure 29.1), and fixed drug eruptions. Old obstetric scars may also pigment. The problem is much more common in those with darker skin. The pigmentation is usually symmetrical but can be very dark. When it is clear that there has been a preceding inflammatory dermatosis, the diagnosis of post‐inflammatory hyperpigmentation is straightforward, but if there is any doubt, or atypical features, a biopsy should be performed. Pigmentation in scars will be linear, and the site helps with diagnosis. The hyperpigmentation is asymptomatic. Figure 29.1 Post‐inflammatory hyperpigmentation after lichen planus. Histologically, there is pigmentary incontinence, with pigment‐laden macrophages in the upper dermis. As with any area of pigmentation, the diagnosis includes melanosis and melanoma. No specific treatment is needed. In many cases, the pigmentation will resolve with time after treatment of the preceding inflammatory problem. The pigmentation may remain, especially in those with darker skin types. Vulval melanosis is a common problem and was the cause of pigmentation in 68% of patients in one series [1]. It is impossible to diagnose safely without histology as the clinical appearances are often alarming. The cause is unknown. Figure 29.2 Histological features of melanosis with increased basal melanin but no increase in melanocytes. Melanosis tends to occur in younger patients. In a series of 129 patients, the mean age at diagnosis was 46 years [2]. Histology shows basal hypermelanosis, sometimes with a slight increase in the number of melanocytes, but no melanocytic proliferation. There are melanophages in the papillary dermis (Figure 29.2). The mucosa is most often affected, particularly the inner labia minora (Figure 29.3). The pigmentation is asymptomatic and is frequently an incidental finding. The clinical appearances are often concerning with irregular, multiple areas which may coalesce, and with variation in depth of pigmentation (Figure 29.4). Dermoscopy can help in diagnosis, with a ring‐like pattern found in about 32% of cases [3]. Reflectance confocal microscopy demonstrates a ringed pattern with polycyclic papillae [4]. This technique showed benign changes in 10 of 17 cases of melanosis, but was able to differentiate these from a case of melanoma [5]. It may be a useful adjunct to indicate the best site for biopsy. However, histological examination is the gold standard investigation. The clinical differential diagnosis is melanoma, and lesions should always be biopsied as the histological pattern of melanosis is typical. Lentigines can often be dark and irregular and part of genodermatoses (see below). No treatment is needed. Figure 29.3 Vulval melanosis. Dark pigmentation upper vestibule. Figure 29.4 Melanosis showing irregular and variable macular pigmentation. There is no evidence that these lesions develop into melanoma. Most are static, and about 30% will change initially but then stabilise, and no malignancy was detected during median follow‐up of 13 years in one large study [2]. In one study of 41 male and female patients with genital melanosis, 5 had a history of melanoma and 1 of these was vulval. However, the melanosis started some years after this and was not thought to be related [6]. Baseline photographs and limited monitoring annually for a few years is generally advised. Dowling‐Degos disease (DDD) is characterised by reticulate pigmentation in the flexures and can also affect the vulval and perianal skin [7]. There is one case where the genital area was the only site involved [8]. The clinical appearances are similar in a range of conditions with different genetic mutations [9]. Classic DDD is caused by mutations in genes encoding for keratin 5 [10]. Galli‐Galli disease is a variant of DDD showing acantholysis [11]. The histology is diagnostic, with irregular elongation of branched rete ridges with a concentration of melanin at the tips (Figure 29.5). The melanocyte count is normal. Figure 29.5 Histology of Dowling‐Degos disease. The epidermis shows branching downgrowths with melanin concentrated at the tips. The pigmentation generally starts in the teens. Small asymptomatic pigmented macules are seen which may take on a reticulate pattern (Figure 29.6). It can be a coincidental finding if the patient develops other symptoms [12]. Other less common features include follicular papules and small pitted scars. In Galli‐Galli disease, the flexural pigmentation is similar, but erythematous papules are seen on the trunk and proximal limbs [13]. The differential diagnosis is melanosis, melanoma, and other lentiginous syndromes. No treatment is needed. The pigmentation can be treated by laser, but this would only be done for cosmetic reasons.
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Disorders of Pigmentation
Hyperpigmentation
Post‐inflammatory pigmentation
Clinical features
Histological features
Differential diagnosis
Treatment
Prognosis and follow‐up
Vulval melanosis
Epidemiology
Histological features
Clinical features
Differential diagnosis
Treatment
Prognosis and follow‐up
Dowling‐Degos disease (reticular pigmented anomaly of the flexures)
Genetics
Histological features
Clinical features
Differential diagnosis
Treatment
Lentigines
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