Summary MRCP Skin Related Diseases

Basics
 Describing a lesion
o Type of lesion
o Colour
o Texture
o Site
o Distribution/Symmetry
o E.g. Maculopapular lesions which is red, smooth, and grouped only on the right wrist


 Colour, Site + Symmetry + Distribution... Type of lesion + SSSCCCTTT

 Type of Lesion
o Macule – circumscribed change in skin colour without elevation

o Papule – solid, elevated lesion which is <0.5cm in diameter
o Nodule – solid, elevated lesion which is >0.5cm in diameter

o Vesicle – circumscribed elevated lesion which contains free fluid and is <0.5cm
 E.g. Herpes (HSV1, HSV2, Varicella Zoster)
o Bulla – circumscribed elevated lesion which contains free fluid and is >0.5cm
o Cyst – Sac containing liquid or semisolid material, usually in dermis
o Pustule – Circumscribed, elevated lesion containing pus

o Plaque – raised lesion which has greater surface area compared to elevation
o Scale – Heaping up of stratum corneum or keratin
o Lichenification – Accentuation of skin markings associated w/ thickening of epidermis

o Ulcer – Loss of epidermis and part of dermis (leaving depressed, moist lesion)
o Erosion – Loss of epidermis ONLY (shallow ulcer)

, Distribution of Lesion
o Discrete – Individual lesion
o Grouped – Multiple, individual lesions on one area
o Generalised – Most of skin of a particular area covered (e.g. generalised over the back)
o Disseminated – Multiple, widespread lesions
o Linear – Forming a line
o Dermatomal – Confined to a dermatome
o Annular – Forming a ring
o Polycyclic – Formic interlinking circles

 Pattern of Lesion
o Symmetrical
o Assymetrical
o Sun-exposed

 Colour of Lesion
o White (depigmented)
o Pale (hypopigmented)
o Dark (hyperpigmented)
o Red (erythematous)
o Brown
o Black

, Skin Layers
o Epidermis – 95% keratinocytes which move up from the Stratum Germinativum (in 4wk)
 Stratum Corneum
 Stratum Lucidium (only in areas of thick skin e.g. sole of foot)
 Stratum Granulosum
 Stratum Spinosum
 Stratum Germinativum/Basale




 Epidermis is avascular; blood supply is from dermal capillaries
 Cells include:
 Keratinocytes – 95%
 Melanocytes
 Langerhans cells (immune function)
 Merkel cells (sensory function)

 Pathology of epidermis:
 Changes in turnover time (e.g. psoriasis [5d vs normal 28d] – rapid turnover)
 Changes in surface or loss of epidermis (e.g. scales, crusting, ulcers/erosions)
 Changes in pigmentation (e.g. hyper – melanoma; hypo – vitiligo)
o Dermis
 Stratum Papillare (highly vascular for dermis + epidermis)
 Stratum Reticulare (highly collagen for structure of skin)

 Pathology of dermis:
 Changes in contour or loss of dermis (e.g. papules, nodules, ulcers)
 Disorders of skin appendages (e.g. hair, sebaceous glands [acne])
 Disorders of blood vessels (e.g. urticaria, purpura)

o Sub-cutaneous tissue

Can Liars Get Skin Grafts (with) Prior Rejection

,  Hair:
o Types: All hair is modified KERATIN w/ shaft + hair bulb (dividing cells + melanocytes for pigment)
 Lanugo – fine, long fetal hair
 Vellus – fine, short hair on all body surfaces
 Terminal – coarse, long hair on scalp, eyebrows, eyelashes, pubic)
o Pathology of hair:
 Reduced or absent melanin pigment (e.g. grey/white hair)
 Changes in growth cycle duration (e.g. hair loss)

 Sebaceous glands  (Sebum producing gland which exits with hair follicle)
o Function: Lubricate + waterproofing of skin
o Pathology of sebaceous glands:
 Increased sebum + bacterial colonisation (acne)
 Sebaceous gland hyperplasia

 Sweat glands:
o Types:
 Eccrine – everywhere in skin, active pre-puberty
 E=everywhere
 APocrine – post-puberty sweating in axilla, genitalia, anus; react w/ bacteria = odor
 A=axillary, P=pubertal areas
o Pathology of sweat glands:
 Inflammation/infection of APOCRINE glands (e.g. hidradenitis suppurativa)
 Overactivity of eccrine glands (e.g. hyperhidrosis  Rx: Topical aluminium chloride)

 Functions of skin**:
o Appearance/cosmesis

o Protection :
 From: UV, mechanical/chemical insult, pathogens, dehydration
 How: Quick turnover + avascularity + Langerhans cells

o Thermal regulation
 How: When cold – hair + adipose; When hot – sweat glands + vascular dilation

o Sensation

o Metabolic function
 Vit D synthesis
 Triglyceride energy storage

 When skin is compromised**:
o Appearance  Plastic surgery or cosmesis
o Protection + Thermal regulation  Wrap in wet cloth or bandaging or other materials to cover
up access for infection
o Sensation  Nil
o Metabolic function  Supplements if necessary