Dermatological conditions in pigmented skin

Diagnosing and managing conditions specific to pigmented skin.

Psoriasis in black populations tends to resist treatment (Picture: Science Photo Library)
Psoriasis in black populations tends to resist treatment (Picture: Science Photo Library)

The term ‘pigmented skin’ refers to Fitzpatrick skin types IV to VI. This encompasses a wide range of ethnic and cultural groups, including Africans, African-Caribbeans, African-Americans, Hispanics, South East Asian, Chinese, Japanese and Native American Indians.1,2

The prevalence and presentation of some skin conditions varies in pigmented skin because of its unique biology and cosmetic practices adopted in these groups.

The percentage of people from non-white ethnic groups in England and Wales increased from 8.7% of the population in 2001 to 14% in 2011.3 Healthcare professionals need to be confident in diagnosing and managing skin conditions in this patient group.

Normal variations of pigmented skin

Some conditions are so common in pigmented skin that they are considered normal variations and patients can be reassured. In all races, the dorsal skin of the limbs is darker than the ventral surfaces. This is more pronounced in pigmented skin, especially the anterolateral portion of the upper arm. These pigmentary demarcation lines (also known as Futcher’s or Voight’s lines) are seen in 20-30% of the black population.4 The lines are symmetrical, bilateral and present from infancy.

Patchy hyperpigmentation can commonly be seen on the palms and soles of black patients. The lesions are usually multiple, of varying sizes, with indistinct borders. They have to be distinguished from acral melanoma, melanocytic naevi and secondary syphilis.

Nail pigmentation is another common clinical sign in patients with pigmented skin – up to 90% of adult African-Americans have one or more pigmented bands.5 This can be seen in childhood, but becomes more obvious with age.

The width of pigmented bands varies from a few millimetres to the whole width of the nail and the colour varies from light brown to black. Pigmentation often affects multiple nails, which helps to distinguish it from subungual haemorrhage, melanocytic naevi and most importantly, melanoma.

Conditions specific to pigmented skin

Tinea capitis
Tinea capitis is an infection of hair follicles and surrounding skin with dermatophyte fungi. Trichophyton tonsurans accounts for 50-90% of dermatophyte scalp isolates in the UK.6 It presents with inflammation, scaling and patchy hair loss.

The condition is most commonly seen in African-Caribbean prepubertal children in urban communities. This is thought to be a result of hairstyling practices, such as close-cropped styles and tight plaits, which make the follicles more vulnerable to infection. Patients are advised against sharing hair clippers because this can spread the infection.7

Mycological confirmation of diagnosis before commencing treatment is recommended. However, treatment should not be delayed if there is strong clinical suspicion. Griseofulvin is the only licensed antifungal for tinea capitis in children in the UK, but the British Association of Dermatologists recommends terbinafine as first-line treatment for Trichophyton species because of its superior cost-effectiveness and safety profile.8

Acne keloidis nuchae
Acne keloidis nuchae is a chronic inflammatory condition usually seen in men of African descent aged 14-25 years. It is rarely seen in prepubertal children and men aged over 50. Close shaving and close-cropped hair are the main risk factors, but friction from shirt collars and helmets has also been implicated.9

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Figure 1: Keloid scarring at hairline typical of acne keloidis nuchae

The condition begins as a chronic folliculitis of the posterior neck and occipital scalp, which progresses to keloidal papules and plaques, causing a scarring alopecia (figure 1). Treatment is difficult and aims to eliminate inflammation at the onset, using potent topical corticosteroids and oral tetracycline antibiotics. Allowing the hair to grow longer is advisable.

Pseudofolliculitis barbae
Pseudofolliculitis barbae is an inflammatory follicular disorder with an estimated prevalence of 45-85% in African-Americans.10 It is most common in men, affecting the beard area or neck, but can also affect women on areas of the body where hair removal practices, such as waxing and shaving, are performed.

It is thought that the natural tendency for curly hair to recoil in this ethnic group predisposes cut hairs to re-enter the skin. As the hair re-enters the dermis, it causes an inflammatory foreign body response, which manifests as papules and pustules. Hyperpigmentation and keloid scarring are frequent complications. Advise patients to allow the hair to grow and modify shaving practices.

Central centrifugal cicatricial alopecia
Central centrifugal cicatricial alopecia is a condition exclusively seen in Fitzpatrick type VI skin. It presents as a diffuse scarring alopecia over the vertex, classically starting in the mid-30s.

Initial hypotheses correlated the condition with heated styling instruments or chemical straighteners. However, it is now thought to be a form of scarring female pattern hair loss.11

Traction alopecia
Traction alopecia is a patchy hair loss caused by hairstyling practices such as ponytails, plaiting and hot combing. It is particularly seen at the frontal and lateral scalp margin. Afro-textured hair is particularly vulnerable to damage by traction.

Long-term, this can result in a scarring alopecia.11 Educating patients about avoiding traumatic hair practices is key in managing both conditions.

Racial variability in common conditions

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Figure 2: Psoriasis in black populations tends to resist treatment

Common skin conditions can be more challenging to diagnose in patients with pigmented skin than in lighter skin types. Skin conditions may follow a different distribution pattern. Hallmark skin signs, such as erythema, can be less obvious, and postinflammatory hyperpigmentation often dominates the clinical picture.12

In psoriasis, for example, the erythema is less apparent and lesions usually have a dark purple hue. Surface scales take on a grey appearance. Other clues, such as scalp and nail changes, can aid diagnosis.

Psoriasis is less prevalent in black populations than in those with lighter skin, but it tends to be extensive and resistant to treatment, often requiring systemic therapy (figure 2).12

Eczema can affect the extensor surfaces of the limbs, particularly at the elbows and knees of patients with pigmented skin. This is known as reverse pattern eczema.13 Lichenification is often a significant feature of the condition and both hyper- and hypopigmentation can be seen (figure 3).

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Figure 3: Lichenified dorsum of hand in a man with eczema

Acne is no more common or severe in pigmented skins, but postinflammatory pigmentation can be significant and often persists for months to years. As such, early and aggressive treatment is advocated, including early referral for consideration of roaccutane. Secondary acne can be a result of cultural practices – hair oil can induce pomade acne on the forehead and skin lightening products containing topical steroids can cause a steroid-induced acne.

Direct questioning about the use of lightening agents is important because patients are usually not forthcoming with this information. Other side-effects of skin lightening agents include tinea incognito, tinea facei, striae, macular hyperchromias and telangiectasia.12

  • Dr Emily Rudd is a dermatology registrar and Dr Claire Fuller is a consultant dermatologist, at Chelsea and Westminster Hospital, London

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References

  1. Taylor SC, Cook-Boden F. Cutis 2002; 69: 435-7
  2. Taylor SC. J Am Acad Dermatol 2002; 46: S41-62
  3. Office for National Statistics 2011 census: key statistics and quick statistics for local authorities in the United Kingdom
  4. Lawrence CM, Cox NH. Physical Signs in Dermatology (second edition). London, Mosby-Wolfe, 2001
  5. Tosti A, Piraccini BM. Nail disorders. In: Bolognia JL, Jorizzo JL, Rapini RP (eds). Dermatology (second edition). Maryland Heights, Mosby Elsevier, 2003
  6. Borman AM, Campbell CK, Fraser M et al. Med Mycol 2007; 45: 131-41
  7. Fuller LC, Child FC, Midgley G et al. Br J Dermatol 2003; 148: 985-8
  8. Fuller LC, Barton RC, Mohd Mustapa MF et al. Br J Dermatol 2014; 171: 454-63
  9. Knable AL Jr, Hanke CW, Gonin R. J Am Acad Dermatol 1997; 37: 570-4
  10. McMichael AJ. Dermatol Clin 2003; 21: 629-44
  11. Sinclair R, Jolliffe V. Fast facts: Disorders of the Hair and Scalp (second edition). Abingdon, Health Press, 2013
  12. Fuller LC, Higgins EM. Racial influences on skin disease. In: Burns T, Breathnach S, Cox N et al (eds). Rook’s Textbook of Dermatology, volume 1 (eighth edition). Oxford, Wiley-Blackwell, 2013
  13. Archer CB, Robertson SJ. Black and White Skin Diseases: An Atlas and Text. Oxford, Blackwell Science, 2008

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