Page 15 - LECTURE NOTES

4. Immunologic: the skin is an end organ for many immunologically mediated

disorders as well as a tool for immunologic research. Because it bears
immunologic cells (lymphocytes, langerhans' cells, and mast cells) it has an active

role in immunologic field of action. The skin can be viewed as a peripheral arm of
the immune system involved in normal homeostasis and host defense.

5. Synthetic function: the skin synthesizes vitamin D, different hormones, melanin,
and other substances.

2.6 Diagnosis

Using the same general principle of clinical diagnosis makes the diagnosis of skin
disease. It begins by taking history, physical examination, and laboratory

investigations when needed.
A proper skin examination should be performed in good light; preferably in daylight.

Ideally the whole skin should be examined.

While describing skin lesions, the following features should be identified:
Sites involved and distribution: - if lesions are affecting both sides of the body

symmetrically, it probably could have an endogenous origin (e.g. eczema, psoriasis,

acne...) but if it involves predominantly one side of the body, usually it could be of
external cause (e.g. bacterial, fungal, contact eczema).

Primary lesions

Macule: flat lesion due to a localized color change only; the surface is normal (size

<1cm)
Patch: similar to a macule but the size (> 1cm)

Nodule: any elevated lesion (> 1cm diameter) which has a round surface (i.e. the

thickness is similar to the diameter): often due to dermal pathology
Plaque: (size > 1cm) a raised lesion where the diameter is much greater than the

thickness
Vesicle: (size < 1cm) a fluid filled lesion (blister)

Bullae: blister which is > 1cm in size

Pustule when a vesicle contains pus and the size is < 1cm and if it is more than 1cm it
is called abscess.

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