Week 2 - F - Hair (Types, phases, alopecia (areata/androgenetic), Drug Eruptions (exanthematous, urticarial, E.M/S.J.S/T.E.N), Flashcards
There are three different types of hair found in humans These are lanugo, vellus and terminal Where is each hair type found? Which hair types growth is influenced by androgens?
Lanugo hairs - fine, long hairs that cover the body of the foetus and will be shed before birth. They will be replaced by…
Vellus hairs - small fine hairs which cover most of the body except eg scalp and pubic area where…
Terminal hairs are found - long and course and growth is influenced by androgen
There are three hair growth phases What are these? (both names)
Anagen - growing phase
Catagen - transitional phase
Telogen - resting (shedding) phase
What happens in each of the stages of the hair cycle?
Anagen (growing phase) - most of the hairs are in anagen phase at any one time (85-90%)
Catagen phase is a short transition between the two
Only 10-15% are in telogen phase at any one time - this is where the hair is shed as the blood supply to hair has been removed
There are different types of hair loss disorders - it is important to take a full history and thorough examination to try and narrow down the differentials Hair loss can be scarring or non-scarring Which is irreversible and what typical disorders can cause this?
Scarring hair loss can cause irreversible hair loss
Some inflammatory dermatoses such as lupus and lichen planus can cause scarring alopecia - look for signs of these disorders elsewhere on the skin
Alopecia is the general medical term for hair loss. There are many types of hair loss with different symptoms and causes. What may alopecia be caused by?
May be caused by eg
- Illness *
- Stress *
- Autoimmune disorder *
- Cancer treatment *
- Iron deficiency
What is alopecia areata? What should you also investigate for if thinking this diagnosis?
Alopeci areata causes smooth round patches of hair loss on the scalp
It has an unkown aetiology however may be autoimmune associated and therefore you should look for other autoimmune disorders such as - type 1 diabetes, pernicious anaemia, autoimmune thyroiditis
Apart from the typical round smooth hair loss patches as seen in alopecia areata, what are other signs of this condition? What is total scalp and total body hair loss known as?
Fine nail pitting
Exclamation mark hairs - hair is dark and thick distally but the thickness and colour reduces as it approaches the follicle
Total scalp hair loss - alopecia totalis
Total body hair loss - alopecia universalis
What is the treatment of alopecia areata?
Regrowth may be spontaneous treatment may involve intralesional steroids, PUVA or a wig
What is androgentic hair loss and who does it affect?
Androgenetic alopecia is a non-scarring form of hair loss that typically affects men but may affect post-menopasualwomen with high androgen levels
In males - Hair is lost beginning above both temples. Over time, the hairline recedes to form a characteristic “M” shape. In females, hair is lost typically on vertex of scalp
What is a treatment for both female and male pattern balding? Try and state the mechanism of action
Male pattern balding - finasteride(5a-reductase inibtor aka dihydrotestosterone blocker - prevents these effects in both BPH and androgenetic alopecia in males) or minoxidil (anti-hypertensive vasodilator)
Females - minoxidil
Drug reactions are a very common reason for referral to dermatology and can be allergic or non-allergic in nature They can range from mild to life threatening What are the usual skin signs of a type 1, 2, 3 and 4 hypersensitivity reaction?
ACID:
* Type 1 - anaphylactic reactions - urticaria *
Type 2 - cytotoxic reactons (antibodies attack self antigens) - pemphigus (Ab against desmoglein 3 - important in desmosomes) and pemphigoid (Ab against hemidesmosomes & basement membrane) *
Type 3 - immune complex mediated reactions - purpura/rash *
Type 4 - T-cell mediated delayed reactions - erythema/rash
Are immunological (allergic) adverse drug reactions or non-immunological (non-allergic) adverse drug reactions dose-dependent for the extent of the cutaneous features?
Immunological reactions are not dose dependent
Non-immunological drug reactions are dose-dependent eg atrophy due to topical corticosteroids
What is the commonest and second most common adverse drug reaction? What is an adverse drug reaction of the skin known as
Most common adverse cutaneous drug reaction is exanthematous (aka maculopapula) drug erutpion
Second most common cutaneous drug reaction is urticarial drug eruption
An adverse drug reaction of the skin is known as a DRUG ERUPTION
In which sex are drug eruptions more common? What is the age group typically affected?
Drug eruptions are more common in females than in males
Young adults > infants/elderly
The most common drug rash is exanthematous drug eruption What type of hypersensitivity are exanthematous drug eruptions and therefore what are they mediated by? What is the presentation of this drug reaction?
Exanthematous drug reaction is type 4 hypersensitivity reaction - it is T cell mediated
Onset is usually 1-3 weeks after first taking drug and causes generalised erythematous macules and papules usually sparing mucous membranes - itch / fever is common
Generalised erythematous maculopapular rash plus itch and fever
Give examples of common offending drugs causing exanthematous drug reactions? What is the treatment?
Penicillins are common offenders
Also anti-epileptics eg carbamezapine usually self limitng
Drug induced urticaria eruption is the second most common adverse drug reaction What are the two ways in which urticarial drug erutptions occur? What type of hypersensitivity?
Drug induced uritcarial eruption is usually due to an immediate IgE hypersensitivity reaction (Type 1) or due to the drugs causing direct release of inflammatory mediators from mast cell degranulation
What is the presentation of urticarial drug reaction? When does it develop? What drugs are causative?
Urticarial drug reactions usually cause wheals +/- associated angio-oedema
Usually develops soon after administration - rechallneging of the drug may result in rash occurrence within minutes
Drugs eg - NSAIDs, opiates
What do erythema multiforme rashes look like? What causes it?
Erythema multiforme is a round erythematous rash with a central blister lesion - aka target lesions
Can occur due to adverse drug reaction eg sulfonamides o anticonvulsants (antibiotic) or due to infection, especially herpes simplex and mycoplasma
What is a rare severe variant of erythema multiforme associated with fever and mucousal involvement however <10% epidermal attachment? Is it usually the drugs (NSAIDs, sulfonamides, anticonvulstants) or infection that cause this?
Steven Johnson syndrome is a rare variant of erythema multiforme associated with fever, mucosal erosions and <10% epidermal detachment It is ususally due to a hypersensitiivty reaction to drugs - NSAIDs, sulfonamides, anti-convulsants
If the epidermal detachment is >30%, what is this known as? How does it present? Why is mortality rate much higher in this condition?
Toxic epidermal necrolysis is where there is >30% epidermal detachment due to an adverse drug reaction (NSAIDs, sulfonamides, anti-convulsants)
Presents with severe mucosal lesions, fever, necrosis of large sheets of epidermis
High mortality due to sepsis
What do lichenoid drug eruptions look like and what drugs can cause it?
Lichenoid drug eruptions are similar to the lichen planus but rarely shows signs of idiopathic lichen planus
Causes itchy, flat-topped, violaceous papules to appear (pruritic, planar, purple, poly-angular, papules)
Caused by eg bblockers and thiazides
If treatment is required for the different drug eruptions, what is usually given? * what can be given for the dryness/itch? * What can be given for IgE mediated eg urticaria?
Most are often self-limiting after cessation of drug *
Emollients can be given for dryness or itch *
Very ithcy eg lichenoid can give course of potent topical steroids eg betnovate (bethametsone valerate) *
Urticaria - anti-histamines are good
For erythema multiformed/Steven Johnson/Toxic epidermal necrolysis - best managed by derm specialists
