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Genital dermatology is both a fascinating and unfamiliar area of medicine to most doctors. Fascinating because the myriad of skin conditions that can afflict that part of the body is simply astounding; unfamiliar because this area is one of the most under-examined parts of the body. This stems from a need to preserve patient’s modesty, avoiding embarrassment, stigma associated with genital conditions, and practitioners’ general discomfort at examining the genital region.

When a patient mentions about a rash “down there”, there is often a reflex association with sexually transmitted infections (STIs). This is, however, not the case. Whilst STIs will often manifest in the genital and perineal area, there are also quite a wide range of non-STI genital dermatoses. These genital dermatoses may occur uniquely to the region, or they may be part of wider dermatoses that also affects other parts of the body.
In this article, we will explore some of the commoner genital dermatoses as well as those with more sinister implications.

I. SEXUALLY TRANSMITTED INFECTIONS (STIs)

The presentation of STIs can broadly be classified into four main groups, namely 1) ulcerative, 2) those with discharges, 3) growths and 4) miscellaneous.

A) Ulcerative STI

• • Ano-Genital Herpes

This is the leading cause of ano-genital ulcer disease worldwide. This is caused by the Herpes Simplex Virus (HSV). HSV, like other members of the herpes family (Herpesviridae), has the ability to remain dormant (ganglion cells in this case) and it can reactivate from time to time. HSV type 2 accounts for the majority of ano-genital herpes, whilst a smaller proportion is due to HSV type 1. Transmission is via direct contact with infected skin or genital fluid, and viral shedding is highest during a disease outbreak.

Herpes outbreak presents with rapidly forming clusters of painful vesicles that would rupture, leaving behind painful shallow erosions over the subsequent days. These erosions generally heal without scarring. Recurrence is common especially during the first two years of infection.

• • Primary Syphilis

Although not strictly an ulcerative STI, syphilis may present as an ulcer (chancre) during the first stage of the infection. During primary syphilis, the patient may notice a solitary ulcer appearing on the genitalia or perineum. This ulcer is generally larger than the erosions seen in ano-genital herpes, and feels indurated when examined. Despite its size and appearance, it is usually painless unless super-imposed by a secondary bacterial infection. As a result, chancres may develop unnoticed by the patient, especially if they occur in the scrotum, perineum, perianal region or vaginal walls. This highlights the importance of a thorough examination; a genital examination should always include the perineum and perianal region.

Patients with untreated primary syphilis may go on to develop secondary syphilis. In secondary syphilis, patients may present with a generalized scaly, erythematous rash or patchy hair loss.

B) Genital Growths

• • Ano-genital Warts

Ano-genital warts are fleshy, warty growths caused by the Human Papilloma Virus (HPV). There are about one hundred strains of HPV that can infect the human skin. In the ano-genital region, certain strains are far commoner. Type 6 and 11 are the commonest non-oncogenic strains, whilst type 16 and 18 are the commonest oncogenic strains affecting the ano-genital region.
Transmission is through direct skin contact of uninfected skin with infected skin. The infected skin does not necessarily need to manifest with clinically apparent disease in order to transmit. HPV infection can occur anywhere in the ano-genital region. Hence, again, the importance of a detailed examination.

• • Molluscum Contagiosum

Molluscum contagiosum (MC) virus belongs to the family of pox viruses. It presents clinically with discrete, pearly, smooth papules, some of which may be umbilicated. It is transmitted via direct skin to skin contact.

C) Other STIs

• • Peduiculosis Pubis
    Patients sometimes may present with a pruritic groin rash, and close examination of the pubic region will reveal the presence of pubic lice (Phthirus pubis). Because pubic lice are well-adapted to the characteristics of pubic hair, they are often sexually transmitted. Occasionally, they may be found in other parts of the body that share similar hair characteristics, such as the axillae, eyelashes and eyebrows.

• Scabies
  Although strictly not a STI, under good sanitary conditions, most adults would acquire scabies sexually. Patients will complain of an extremely pruritic skin eruption that affects the groin which can then quickly spread to the rest of the body. Because it is highly contagious, household members often need to be screened and started on prophylactic treatment.

II. NON-STI GENITAL DERMATOSES

The wide range of non-STI genital dermatoses include inflammatory dermatoses, pigmentary disorders, iatrogenic conditions, non-STI infections, pre-malignant and malignant conditions as well as benign variations of normal anatomy. Because of space constraint, this article will highlight the more important or common conditions.

A) Inflammatory Dermatoses

• • Psoriasis

Psoriasis is a systemic inflammatory condition that often presents with a skin rash and sometimes joint involvement. The typical rash is that of thickened erythematous plaques with silvery scales on the extensors and the scalp. It can sometimes affect the genitalia. Common genital sites include the glans penis, scrotum, vulva and the pubis

• • Lichen Planus

This is another inflammatory skin condition that presents with discrete violaceous, shiny, flat-topped plaques with may be pruritic. Common sites include the wrist, buccal mucosa and penile shaft and glans penis.

• • Behcet’s Disease

This inflammatory condition is characterised by recurrent painful oral and genital ulcers that may heal with scarring. It may be accompanied by other skin manifestations such as erythema nodusum, acneiform lesions and pseudo-folliculitis.

• • Lichen sclerosus

Lichen sclerosus is a slow chronic inflammatory dermatosis that presents with ivory-white sclerotic plaques on the genitalia. Common sites include the vulva, prepuce and frenulum. In advanced stages, there may be distortion of the normal architecture with loss of the usual vulva folds or frenulum. There is a risk of malignant change in chronic lesions.

• • Zoon’s balanitis

This is a benign, plasma cell-mediated inflammatory dermatosis presenting usually as a solitary smooth, ill-defined erythematous patch on the glans penis. As this is often clinically indistinguishable from erythroplasia of Queyrat (see below), a skin biopsy is usually warranted. Treatment is with topical creams and prognosis is excellent.

B)Pre-malignant and Malignant Dermatoses

• • Erythroplasia of Queyrat

Erythroplasia of Queyrat is also known as squamous cell carcinoma in-situ of the skin occurring in the glans penis. Patients may present with a moist, superficially eroded patch on the glans penis. As it is indistinguishable from the benign Zoon’s balanitis, a skin biopsy is imperative, as it determines very different management of the condition. A skin biopsy should be considered in any case of a long-standing, non-healing balanitis.
Fig. H. Erythroplasia of Queyrat. Similar moist erythematous plaque on the glans penis. A biopsy is needed to distinguish this from the benign Zoon’s balanitis.

• • Squamous Cell Carcinoma of the Skin

This is the classical squamous cell carcinoma of the skin. It can affect the genitalia, presenting as a highly irregular, variegated hypertrophic plaque.

• • Extra-mammary Paget’s disease

Extra-mammary Paget’s disease (EMPD) often presents as a long-standing, poorly healing eczematous plaque on the scrotum or vulva that does not respond well to eczema treatment (see lichen simplex chronicus).

EMPD is a type of cutaneous adenocarcinoma. Whilst it is often a primary cutaneous adenocarcinoma, secondary EMPD may account for about a quarter of EMPD patients. In such cases, the primary lesions are usually visceral malignancies arising from the urogenital or lower gastrointestinal tract. Hence, all patients diagnosed with EMPD would require careful evaluation of these organ systems.

C) Other Genital Dermatoses

• • Lichen simplex chronicus

Lichen simplex chronic (LSC) is a type of endogenous eczema. Patients often complain an intensely pruritic patch of rash in the groin area. Repeated scratching often leads to thickening of the affected skin with increased skin folds. Treatment of LSC is the same as for endogenous eczema. Breaking the itch-scratch-itch cycle is important in LSC management

• • Fixed Drug Eruption

Whilst we are familiar with the mucosal involvement in erythema multiforme (EM) and Steven-Johnson Syndrome (SJS), cutaneous drug rash may present in a myriad of ways. Fixed drug eruption (FDE) is a type of cutaneous drug eruption that is more likely to present to primary health care.
Patients with FDE will present with erythematous erosions on the glans penis and prepuce that is followed by crusting and desquamation. FDE has a predilection for the lips and genitalia.
An antecedent drug use will be highly suggestive. Common offending drugs include tetracyclines, co-trimoxazole, penicillins, aspirins, NSAIDs and paracetamol.

SUMMARY

There is more to genital dermatoses than just sexually transmitted infections. Unfortunately, due to factors inherent to its location, this area of the body is often under-examined and under-diagnosed. As STI is part of dermatology training, it may be prudent to send patients to a dermatologist when in doubt.

References

1. http://www.dermnetnz.org/
2. http://emedicine.medscape.com/