How to spot a rash part 2: examining a patient with a skin problem


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By Rod Tucker
Community pharmacist

13 Feb 2019

Once you’ve taken a patient’s history of skin complains, you can start to look more closely at the problem at hand, writes Rod Tucker

 

Establishing a dermatological diagnosis is largely based on ‘pattern recognition’ and it is therefore vital to be able to look closely at the patient’s skin. Experienced dermatologists can usually ‘spot’ a diagnosis after a brief inspection of the skin lesion or rash but the novice needs to adopt a systematic approach to examination in combination with a good history.

In order to respect a patient’s privacy, any examination – especially one that requires the patient to remove items of clothing – should be conducted in the consultation room. Pharmacists always need to ask patients if they want a chaperone and ideally, to protect the patient from vulnerability and embarrassment, the chaperone should be of the same sex. If no suitable person is available, a pharmacist should offer to delay or re-arrange any examination.

 

Before the examination

 

Prior to looking at the skin, try and gauge the patient’s sense of wellbeing, ie do they appear well or seem ill? This may indicate the presence of a systemic illness that gives rise to cutaneous symptoms eg septicaemia. Start by taking a history and ask all the relevant questions. This may offer important clues and the examination will then serve to confirm the diagnosis.

The skin should be clear of any creams, make-up or any other covering agents that limit your ability to fully inspect the affected area. In practice this can sometimes be difficult. For instance, a teenage girl seeking advice about her acne will probably be using make-up to cover her spots. Finally, aim to examine the skin in good light, preferably daylight if not the bright light in a consultation room.

Pharmacists don’t need to wear gloves when examining a patient. In fact, the use of gloves instantly makes the patient think that their problem is infectious. Gloves are definitely required for an intimate examination, although this is unlikely in a pharmacy.

Dermatologists and specialist GPs will use specialist equipment such as a Wood’s lamp to identify conditions such as melasma and vitiligo and a dermascope to help diagnose pigmented lesions. While these are invaluable for the expert, unless the pharmacist has received additional training, they are unnecessary for a basic examination. Possession of a simple magnifying lens is perhaps the most useful because subtle changes in the skin become more apparent when enlarged.

 

What to consider during an examination:

 

Site and distribution

 

A number of skin conditions typically affect specific areas of the body and knowing this can help to establish the diagnosis. It is useful to stand back from the patient and consider the distribution of the problem. For example, note whether it affects flexor or extensor surfaces. As an example, atopic eczema in children is characteristically seen on flexor surfaces such as the inner elbow creases and behind the knees. In contrast, psoriasis is normally found occur on extensor surfaces of the elbows and knees.

A further relevant point is symmetry, ie does the problem affect both sides of the body? A symmetrical skin problem frequently indicates an endogenous cause, ie atopic eczema will be seen on both elbow creases. In contrast, an asymmetric rash, eg affecting a single arm, hand, leg etc, is most likely to have an external cause.

When a rash appears localized to a specific area of skin, this can often help establish the probable cause. Instances where the rash can be attributed to a specific cause include:

 

  • A facial rash that spares the area of skin under the chin and behind the ears is potentially a photo-sensitive reaction
  • A problem that follows a path along a dermatome, such as along the side of the chest, patients might have herpes zoster (shingles).
  • A linear eruption at a site of skin trauma or a scar is termed the Koebner phenomenon and can be seen in patients with psoriasis.
  • Several itchy papules close together for example on the lower leg may indicate insect bites.

 

Finally, if based on your examination, you have a hunch as to the most likely cause, look for any other features to support the diagnosis. For example, a scaly rash on both elbows, is conceivably psoriasis hence looking for similar signs on the knees and scalp and pitting in the fingernails.

 

Shape and border

 

The shape and border of some skin conditions are characteristic, eg discoid eczema lesions are normally highly pruritic, coin-shaped on the limbs rather than the trunk. The border of a patch of psoriasis is well-defined. In contrast, atopic eczema affecting the inner elbow creases typically fades into the surrounding skin.

 

Colour

 

Not all skin problems are red! The term erythema describes redness of the skin and is an example of when pharmacists should touch a patient. Erythema is caused by vasodilatation that blanches on pressing. In contrast, purpura is non-blanching and due to extravasation of blood, ie leakage into the surrounding tissue.

Other changes in skin colour can result yeast infections such as pityriasis versicolor which causes hypopigmentation, ie areas of paler skin and the autoimmune disorder, vitiligo, which causes depigmentation or loss of colour. An increased pigmentation (hyperpigmentation) is seen with melasma.

 

Terminology

 

It is important to have a basic grasp of the language used by dermatologists to describe a skin problem as well as the names of the different types of lesions present.

Skin lesions are classified as either primary or secondary. A primary lesion is the earliest physical finding on examination whereas a secondary lesion develops as the skin condition evolves.

 

 Case study

 

One afternoon, Mary, a 42-year old local school teacher, comes to see you about a rash on her lower leg. She describes how the area is very itchy sometimes, causing her to scratch and vigorously rub it. She remembers being bitten, probably by a flea, from her neighbour’s cat and that she couldn’t stop scratching it. Mary is concerned because the redness has increased in size and has become increasingly itchy. There is school inspection soon and she explains how this lesion is just adding to her stress. She has no other current medical problems but had atopic eczema as a child and teenager and her father suffered from psoriasis.

Mary’s skin problem shows evidence of scaling, lichenification and excoriations due to scratching which is the clearest evidence that the lesion is highly pruritic. The family history include both eczema and psoriasis and the lesion has a well-defined border which is characteristic of psoriasis rather than eczema. However, this is an asymmetric, isolated lesion and the absence of similar lesions elsewhere makes a diagnosis of psoriasis unlikely.

A clue to the possible cause comes from the history. Mary reported having had an insect (possibly, a flea) bite which created a pruritic region of skin on her lower leg. Bites are very itchy but repeated scratching aggravates the skin and creates a vicious ‘scratch-itch’ cycle which over time has led to lichenification (skin thickening). In this case the most likely diagnosis is lichen simplex, sometimes referred to as neurodermatitis and it occurs more frequently in those with eczema and people who are stressed or anxious which fit with Mary’s current situation and history. Treatment is directed at relieving the pruritus and will include topical steroids and liberal use of emollients.

 

Read the first part of this article here

 

Rod Tucker is a community pharmacist

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