CPD I: dermatology lecture I

This was the first lecture of second year, from the major class of this year: clinical physical diagnosis (CPD). We dove into dermatology and the diagnosis of different skin lesions. First we talked about different factors to consider when diagnosing a lesion, such as appearance, time factors, spreading, sensation, change, previous treatment. In general the questions of diagnosis seem to fall under the categories: What is it? How did it develop? What's been done to treat it? What are other internal or hereditary factors to consider? What are some external or environmental factors to consider? What do the other organ systems in the body indicate?

Then we talked about the actual classification of different skin lesions. "Primary morphology" refers to the particular type of skin lesions, such as a bullae, papule, macule, scaling, erosion, etc. "Secondary morphology" refers to the overall shape / distribution of the lesions, such as linear, annular, nummular, serpiginous. Other factors used to distinguish between lesions are: color, texture, location, clinical manifestations. Here are examples of what different colors indicate:

Red: erythema
Orange: hypercarotenemia
Yellow: jaundice
Green: pseudomonas
Violet: port wine stain
Grey/Blue: anemia
Black: melanocyte pathology or arterial insufficiency.

Some other terms to know:

Nummular: circular lesions with lighter center
Verrucous: Irregular texture
Lichenification: thickened texture
Induration: deeper lichenification

A number of tests are available to distinguish between these lesions, such as biopsies, KOH test (for yeast, fungus), wood's lamp (UV light which detects certain fungal infections), diascopy (glass slide test for blanching), immunoflourescence test, ESR, ANA tests.

We started looking at Acne Vulgaris and Rosacea, two common skin pathologies. Acne vulgaris is commonly caused by androgen hormones or bacterial interaction with the skin, which leads to the obstruction of the pilosebaceous unit, which leads to different lesions such as comedones, nodules, papules, cysts, pustules, and purulent sacs. It can have similar manifestations to perioral dermatitis, drug eruptions, and rosacea.

Rosacea, on the other hand, is a different pathology which can start with flushing of the skin, and can progress to telangectasia (tortuous vessels), papules/pustules, and at its worst, rhinophyma (excess collagen deposition and hyperplasia of sebaceous glands). The differential diagnosis for rosacea: SLE, discoid lupus, acne, drug eruptions, perioral dermatitis.