Dermatology Intro 2 Flashcards
What are the functions of the hair? ( 6 )
- Protection against external factors
- Sebum
- Apocrine sweat
- Thermoregulation
- Social and sexual
interaction - Epithelial and melanocyte stem cells
What are Terminal hairs?
Hair on the scalp, eyebrows and eyelashes
What are Vellus hairs?
Rest of the body ( except palms, soles, lips, external genitalia )
Describe the three phases of the hair cycle
(85%) Anagen : new hair forms and grows 2-6 years
(1%) Catagen: regressing phase, 3 weeks
(10-15%) Telogen: resting phase, 3 months
Describe the structure of hair in the skin?
Pockets of epithelium continuous with superficial epidermis
Human skin contains pilosebaceous follicles and sweat glands.
Envelop a small papilla of dermis at their base.
Arrector pili (smooth muscle) extends at angle between surface of dermis and point in follicle wall.
What is the Holocrine sebaceous gland?
( sebaceous gland is a type of holocrine gland because it release sebum which is dead reminent of the gland itself )
Open up into pilary canal which drains into axillae. releases sebum
- follicles are associated with aporcine glands
What is the infundibulum?
Uppermost portion of the hair follicle extending from opening of sebaceous gland to surface of the skin
What is the Isthmus?
Lower portion of upper part of hair follicle between opening of sebaceous gland and insertion of arrector pili muscle
- between the infundibulum and suprabulbar region
Epithelium keratinization begins with lack of granular layer named
What is the bulge?
Segment of the outer root sheath located at insertion of arrector pili muscle
Hair follicle stem cells reside here
Why may the bulge migrate down?
Downward → generate the new lower anagen hair follicle → enter hair bulb matrix, proliferate and undergo terminal differentiation to form hair shaft and inner root sheath.
Why may the bulge migrate up?
Upwards (distally) → form sebaceous glands and to proliferate in response to wounding
What is the bulb?
Lower most portion of the hair follicle, includes the follicular dermal papilla and the hair matrix
What is the outer root sheath
Extends along from the hair bulb to the infundibulum and epidermis serves as a reservoir of stem cells
Inner root sheath
What is the Inner root sheath
Guides / shapes hair
Encloses follicular dermal papilla, mucopolysaccharide-rich strome, nerve fiber and capillary loop.
What are the functions of the nails? ( 5 )
Protection of underlying distal phalanx
Counterpressure effect to pulp important for walking and tactile sensation
Increase dexterity / manipulation of small objects
Enhance sensory discrimination
Facilitate scratching or grooming
What is the nail plate?
Final product of proliferation and differentiation of nail matrix
keratinocytes
Emerges from proximal nail fold
Grows at 1-3mm/month
Firmly attached to nail-bed
Detaches at hyponychium
Lined laterally by lateral nail folds
What does the nail matrix do?
Produces nail plate
Nail matrix keratinocytes differentiate → lose their nuclei and are strictly adherent - cytoplasm completely filled by hard keratins
Also contains melanocytes
Lies under proximal nail fold, above bone of distal phalanx (to which it is connected by a tendon
Lunula only visible proportion
What are the characteristics of Psorasis?
Chronic, immune mediated disorder
Have polygenic predisposition but environmental trigger needed.
Demarcated, scaly, erythematous plaques
Common sites are scalp, elbows and knees, nails, hands, feet and trunk (including intergluteal fold)
Describe the pathophysiology of Psoriasis
Keratinocytes put under ‘stress’ and release DNA
Forms complex with antimicrobial peptides
Induce cytokines - TNF-alpha, IL-1, IFN-alpha to activate dermal dendritic cells
dDCs go to lymph nodes, cause Th1, Th17, Th22 cells to release chemokines.
Inflammatory cells move into dermis and release their own cytokines
Results in keratinocyte proliferation - plaque
What cause cause keratinocyte ‘stress’?
Trauma, pathogens
What systemic manifestations may occur due to psoriasis?
Psoriatic arthritis is most common systemic manifestation - linked to nail psoriasis
Liver inflammation
What is Guttate Psoriasis?
Follows a streptococcal throat infection
teardrop shapes rash
How to manage Psoriasis?
Secondary prevention - stop aggrevating factors:
Alcohol, Smoking
Co-morbidities risk should be managed
Psychologist
( anti TNF
What medication can be given for Psoriasis? - 1st line
First line : topical treatments - steroids, VD analogue, retinoids, topical tacrolimus/pimecrolimus
Phototherapy:
- Narrowband UVB
- PUVA (Psoralen + UVA) ( increased risk of skin cancer )
What 2nd Line treatments are available for Psoriasis?
Acitretin
- Systemic immunosuppression
- Methotrexate
- Ciclosporin
Advanced therapies
-PDE4 inhibitors (Apremilast) inhibits TNF
-Biologics (anti-TNF-α, anti-IL-17, anti-IL23) monoclonal antibodies
0JAK inhibitors
What are the characteristics of Atopic Eczema?
- Intensely pruritic chronic inflammatory condition
- Complex genetic disease with environmental
influences - Infancy or early childhood
- Often associated with other ‘atopic’ disorders e.g. asthma, rhinoconjunctivitis
- Acute inflammation of cheeks, scalp and extensors in infants
- Flexural inflammation and lichenification in children and adults
- Daily emollients and anti-inflammatory therapy are cornerstone of management
Eczema barrier defect pathophysiology?
- Filaggrin not working: bind and aggregate keratin bundles and intermediate filaments forming cellular scaffold in corneocytes
- Reduced extracellular lipids and impaired ceramide production
- Increased transepidermal water loss
- Lack of protection from microbes and allergens
Eczema immune dysregulation pathophysiology?
- Staphylococcal superantigens stimulate Th2 lymphocyte
responses and subvert T‐reg - T-cell infiltrate - bias towards Th2 responses
Role of microbiome?
Eosinophils
Clinical features of Eczema(s)?
Infantile phase : Erythematous, Odematous pupale, plaques on face and limbs
Childhood/ adult : Lichenification, crusting, excoriation and dyspigmentation
Fissuring
Allergic contact dermatitis
Impetignisation - gold crust staphylococcus aureus
venous stasis eczema
What is a clinical feature of emergency Eczema
Eczema herpeticum
Monomorphic Errosions in epidermis
How to manage Atopic Eczema?
- Emollients
- Omission of soap
- Clinical Nurse Specialist involvement
- technique
- Day treatment
- Habit reversal
- Co-morbidities
- Patch testing
- Biopsy ( nipple eczema may be cancer)
What Topical Medicines are there for Eczema?
- Topical corticosteroids - correct potency for correct site
- Topical tacrolimus / pimecrolimus
Phototherapy:
- Narrowband UVB
- PUVA (hand dermatitis)
Which topical steroids are available for eczema?
Least potent:
Hydrocortisone Clobetasone etamethasone Mometasone Clobestaol
Most potent
2nd line management for Eczema?
Retinoids (hand dermatitis)
Systemic immunosuppression Methotrexate Ciclosporin Azathioprine Mycophenolate mofetil
Advanced therapies
Biologics (anti-IL-4α, anti-IL13)
JAK inhibitors
