introduction to dermatology part 2

Question 1

what are the functions of the hair?

Answer 1

Protection against external factors
Sebum
Apocrine sweat
Thermoregulation
Social and sexual interaction
Epithelial and melanocyte stem cells

Question 2

what are the thick hairs on scalp, eyebrows and eyelashes called?

Answer 2

terminal hairs

Question 3

what are the hairs on the rest of the body called?

Answer 3

vellus hairs (not found on palms, soles, mucosal regions of lips and external genitalia)
thinner

Question 4

what are the phases of the hair cycle?

Answer 4

anagen
catagen
telogen
(then loss of hair)

Question 5

outline the anagen phase

Answer 5

(where new hair forms and grows)

85% of hair; lasts 2-6 years

Question 6

outline the catagen phase

Answer 6

(regressing phase)

1% of hair; lasts 3 weeks

Question 7

outline the telogen phase

Answer 7

(resting phase)

10-15% of hair; lasts 3 months

Question 8

what is the infundibulum?

Answer 8

Uppermost portion of the hair follicle extending from opening of sebaceous gland to surface of the skin

Question 9

what is the isthmus?

Answer 9

Lower portion of upper part of hair follicle between opening of sebaceous gland and insertion of arrector pili muscle
Epithelium keratinization begins with lack of granular layer named “trichilemmal keratinization”

Question 10

what is the bulge?

Answer 10

Segment of the outer root sheath located at insertion of arrector pili muscle
Hair follicle stem cells reside here
Migrate:
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.
Upwards (distally) → form sebaceous glands and to proliferate in response to wounding

Question 11

what is the bulb?

Answer 11

Lower most portion of the hair follicle, includes the follicular dermal papilla and the hair matrix

Question 12

what is the outer root sheath?

Answer 12

Extends along from the hair bulb to the infundibulum and epidermis serves as a reservoir of stem cells

Question 13

what is the inner root sheat?

Answer 13

Guides / shapes hair

Encloses follicular dermal papilla, mucopolysaccharide-rich strome, nerve fiber & capillary loop.

Question 14

what are the functions of the nails?

Answer 14

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

Question 15

what are the 2 main parts of the nail?

Answer 15

nail plate

nail matrix

Question 16

what is the nail plate?

Answer 16

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

Question 17

what is the nail matrix?

Answer 17

Produces nail plate
Lies under proximal nail fold, above bone of distal phalanx (to which it is connected by a tendon
Lunula only visible proportion
Nail matrix keratinocytes differentiate → lose their nuclei and are strictly adherent - cytoplasm completely filled by hard keratins
Also contains melanocytes

Question 18

give an overview of psoriasis

Answer 18

Chronic, immune-mediated disorder
Polygenic predisposition combined with environmental triggers, e.g. trauma, infections, or medications
Pathophysiology involves T-cells and their interactions with dendritic cells and cells involvement in innate immunity, including keratinocytes
Sharply demarcated, scaly, erythematous plaques characterise the most common form of psoriasis
Common sites of involvement are scalp, elbows and knees, followed by nails, hands, feet and trunk (including intergluteal fold)
Psoriatic arthritis is most common systemic manifestation

Question 19

outline the pathophysiology of psoriasis

Answer 19

Stressed keratinocytes release DNA / RNA → form complex with antimicrobial peptides → induce cytokines (TNF-α, IL-1 and IFN-α) production → activate dermal dendritic cells (dDCs)

dDCs migrate to lymph nodes → promote Th1, Th17, Th22 cells → chemokine release – migration of inflammatory cells into dermis → cytokine release → keratinocyte proliferation → psoriatic plaque

Question 20

what are the clinical features of psoriasis?

Answer 20

red patches
scales of keratin
pitting of nails
oil stains on nails due to lifting

Question 21

how is psoriasis managed?

Answer 21

reduce alcohol and smoking

Therapeutic ladder
Topical therapies
Vitamin D analogues
Topical corticosteroids
Retinoids
Topical tacrolimus / pimecrolimus

Phototherapy
Narrowband UVB
PUVA (Psoralen + UVA)

Acitretin

Systemic immunosuppression
Methotrexate
Ciclosporin

Advanced therapies
PDE4 inhibitors (Apremilast)
Biologics (anti-TNF-α, anti-IL-17, anti-IL23)
JAK inhibitors

Question 22

give an overview of atopic eczema

Answer 22

Intensely pruritic chronic inflammatory condition
Complex genetic disease with environmental influences
Typically beings during 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 (dermatitis) - umbrella term: atopic eczema, seborrhoiec dermatitis, venous stasis eczema, allergic contact dermatitis, irritant contact dermatitis

Question 23

outline the pathophysiology of atopic eczema

Answer 23

Barrier defect
Filaggrin - bind and aggregate keratin bundles and intermediate filaments to form cellular scaffold in corneocytes
Reduced extracellular lipids and impaired ceramide production
Increased transepidermal water loss (TEWL)
Impaired protection against microbes and environmental allergens
Immune dysregulation
Staphylococcal superantigens stimulate Th2 lymphocyte responses and subvert T‐reg
T-cell infiltrate - bias towards Th2 responses
Role of microbiome?
Eosinophils

Question 24

what are the clinical features of atopic eczema?

Answer 24

Infantile phase atopic dermatitis: erythematous, oedematous papule & plaques ± vesiculation

thickening of skin and dispigmentation

fissuring

Question 25

how do you manage atopic eczema?

Answer 25

Lifestyle
Emollients
Omission of soap

Clinical Nurse Specialist involvement
Topical application technique
Day treatment
Habit reversal

Co-morbidities

Patch testing

Biopsy

Therapeutic ladder-
Topical therapies
Topical corticosteroids - correct potency for correct site
Topical tacrolimus / pimecrolimus

Phototherapy
Narrowband UVB
PUVA (hand dermatitis)

Retinoids (hand dermatitis)

Systemic immunosuppression
Methotrexate
Ciclosporin
Azathioprine
Mycophenolate mofetil

Advanced therapies
Biologics (anti-IL-4α, anti-IL13)
JAK inhibitors