Dermatology Flashcards
Onychomycosis - causes, risk factors, features , DD, investigation, management
Onychomycosis is fungal infection of the nails. This may be caused by
- dermatophytes - mainly Trichophyton rubrum, accounts for 90% of cases
- yeasts - such as Candida
- non-dermatophyte moulds
Risk factors include for fungal nail infections include diabetes mellitus andincreasing age.
Features
- ‘unsightly’ nails are a common reason for presentation
- thickened, rough, opaque nails are the most common finding
Differential diagnosis
- psoriasis
- repeated trauma
- lichen planus
- yellow nail syndrome
Investigation
- nail clippings
- scrapings of the affected nail
- the false-negative rate for cultures are around 30%, so repeat samples may need to be sent if the clinical suspicion is high
Management
- do not need to be treated if it is asymptomatic and the patient is not bothered by the appearance
- diagnosis should be confirmed by microbiology before starting treatment
- dermatophyte infection:
- -oral terbinafine is currently recommended first-line with oral itraconazole as an alternative
- -6 weeks - 3 months therapy is needed for fingernail infections whilst toenails should be treated for 3 - 6 months
- -treatment is successful in around 50-80% of people
- Candida infection:
- -mild disease should be treated with topical antifungals (e.g. Amorolfine) whilst more severe infections should be treated with oral itraconazole for a period of 12 weeks
- if topical topical treatment is given treatment should be continued for 6 months for fingernails and 9-12 months for toenails
Lichen planus - Features, causes, management
Lichen planus is a skin disorder of unknown aetiology, most probably being immune-mediated.
Features
- itchy, papular rash most common on the palms, soles, genitalia and flexor surfaces of arms
- rash often polygonal in shape, with a ‘white-lines’ pattern on the surface (Wickham’s striae)
- typically a symmetrical white lace-like pattern on the buccal mucosa
- Koebner phenomenon may be seen (new skin lesions appearing at the site of trauma)
- oral involvement in around 50% of patients: typically a white-lace pattern on the buccal mucosa
- nails: thinning of nail plate, longitudinal ridging
Lichenoid drug eruptions - causes:
- gold
- quinine
- thiazides
Management
- topical steroids are the mainstay of treatment
- benzydamine mouthwash or spray is recommended for oral lichen planus
- extensive lichen planus may require oral steroids or immunosuppression
Nail signs ?
Nail pitting
- psoriasis
- alopecia areata
Blue nails
- Wilson’s disease
Leuconychia
- hypoalbuminaemia
- less common: fungal disease, lymphoma
Half and half
- distal portion brown and proximal portion pale
- chronic renal failure
Nail patella syndrome
Yellow nail syndrome
- associated with congenital lymphoedema, pleural effusions, bronchiectasis and chronic sinus infections
Contact dermatitis
There are two main types of contact dermatitis
irritant contact dermatitis:
- common - non-allergic reaction due to weak acids or alkalis (e.g. detergents). Often seen on the hands. Erythema is typical, crusting and vesicles are rare
- allergic contact dermatitis: type IV hypersensitivity reaction. Uncommon - often seen on the head following hair dyes. Presents as an acute weeping eczema which predominately affects the margins of the hairline rather than the hairy scalp itself. Topical treatment with a potent steroid is indicated
Cement is a frequent cause of contact dermatitis. The alkaline nature of cement may cause an irritant contact dermatitis whilst the dichromates in cement also can cause an allergic contact dermatitis
Patch testing is the investigation of choice for suspected allergic contact dermatitis. Various allergens are applied to the patient’s back, and the skin assessed at 48 hours and 7 days for any reaction. Standard batteries of allergens are used, in addition to samples of any substances the patient suspects.
What is purpura?
Purpura describes bleeding into the skin from small blood vessels that produces a non-blanching rash. Smaller petechiae (1-2 mm in diameter) may also be seen. It is typically caused by low platelets but may also be seen with bleeding disorders, such as von Willebrand disease.
It is important to recognise purpura as it can indicate the presence of serious underlying disease. Children with a new purpuric rash should be admitted immediately for investigations as it may be a sign of meningococcal septicaemia or acute lymphoblastic leukaemia. Parenteral antibiotics should be given prior to transfer if meningococcal septicaemia is suspected.
Causes of purpura? in children
Meningococcal septicaemia • Acute lymphoblastic leukaemia • Congenital bleeding disorders • Immune thrombocytopenic purpura • Henoch-Schonlein purpura • Non-accidental injury
Causes of purpura? in adults
- Immune thrombocytopenic purpura
- Bone marrow failure (secondary to leukaemias, myelodysplasia or bone metastases)
- Senile purpura
- Drugs (quinine, antiepileptics, antithrombotics)
- Nutritional deficiencies (vitamins B12, C and folate)
Raised superior vena cava pressure (e.g. secondary to a bad cough) may cause… ?
Petechiae in the upper body but would not cause purpura.
When is purpura a normal finding in children?
Purpura are never a normal finding in children
- needs to be immediately admitted to exclude ALL and meningococcal disease
Leukoplakia
Leukoplakia is a premalignant condition which presents as white, hard spots on the mucous membranes of the mouth. It is more common in smokers.
Leukoplakia is said to be a diagnosis of exclusion. Candidiasis and lichen planus should be considered, especially if the lesions can be ‘rubbed off’
Biopsies are usually performed to exclude alternative diagnoses such as squamous cell carcinoma and regular follow-up is required to exclude malignant transformation to squamous cell carcinoma, which occurs in around 1% of patients.
The difference between features of leukoplakia and candidiasis?
The asymptomatic and prolonged nature of the symptoms goes against a diagnosis of candidiasis
Hyperhidrosis - management
Management options include
- topical aluminium chloride preparations are first-line. Main side effect is skin irritation
- iontophoresis: particularly useful for patients with palmar, plantar and axillary hyperhidrosis
- botulinum toxin: currently licensed for axillary symptoms
- surgery: e.g. Endoscopic transthoracic sympathectomy. Patients should be made aware of the risk of compensatory sweating
1st line - aluminium chloride
2nd line - Botulinum toxin injections and topical glycopyrrolate (an antimuscarinic agent)
Causes of pruritus ? Features?
- Liver disease - History of alcohol excess
Stigmata of chronic liver disease: spider naevi, bruising, palmar erythema, gynaecomastia etc
Evidence of decompensation: ascites, jaundice, encephalopathy - Iron deficiency anaemia - Pallor
Other signs: koilonychia, atrophic glossitis, post-cricoid webs, angular stomatitis - Polycythaemia - Pruritus particularly after warm bath
‘Ruddy complexion’
Gout
Peptic ulcer disease
Blood results - increased Hb, platelets, WBC - Chronic kidney disease -Lethargy & pallor (anaemia as. a result of a lack of EPO - more likely to be a normochromic normocytic anaemia )
Oedema & weight gain
Hypertension
- Lymphoma - Night sweats Lymphadenopathy Splenomegaly, hepatomegaly Fatigue Deranged WBC Low platelets
Other causes: hyper- and hypothyroidism diabetes pregnancy 'senile' pruritus urticaria skin disorders: eczema, scabies, psoriasis, pityriasis rosea
Skin disorders associated with SLE
Skin manifestations of systemic lupus erythematosus (SLE) - photosensitive 'butterfly' rash (the malar rash has nasolabial sparing) - discoid lupus - alopecia - livedo reticularis: net-like rash
Bullous pemphigoid- feature , investigation finding, mx
Bullous pemphigoid is an autoimmune condition causing sub-epidermal blistering of the skin. This is secondary to the development of antibodies against hemidesmosomal proteins BP180 and BP230
Bullous pemphigoid is more common in elderly patients. Features include
- itchy, tense blisters typically around flexures
- the blisters usually heal without scarring
- mouth is usually spared*
(*in reality around 10-50% of patients have a degree of mucosal involvement. It would however be unusual for an exam question to mention mucosal involvement as it is seen as a classic differentiating feature between pemphigoid and pemphigus.)
Skin biopsy
- immunofluorescence shows IgG and C3 at the dermoepidermal junction
Management
- referral to dermatologist for biopsy and confirmation of diagnosis
- oral corticosteroids are the mainstay of treatment
- topical corticosteroids, immunosuppressants and antibiotics are also used
Squamous cell carcinoma of the skin - risk factors, treatment, good/poor prognosis factors
Squamous cell carcinoma is a common variant of skin cancer. Metastases are rare but may occur in 2-5% of patients.
Risk factors include:
- excessive exposure to sunlight / psoralen UVA therapy
- actinic keratoses and Bowen’s disease
- immunosuppression e.g. following renal transplant, HIV
- smoking
- long-standing leg ulcers (Marjolin’s ulcer)
- genetic conditions e.g. xeroderma pigmentosum, oculocutaneous albinism
Treatment:
Surgical excision with 4mm margins if lesion <20mm in diameter. If tumour >20mm then margins should be 6mm. Mohs micrographic surgery may be used in high-risk patients and in cosmetically important sites.
Good prognosis:
- Well differentiated tumours
- <20mm diameter
- <2mm deep
- No associated diseases
Poor prognosis:
- Poorly differentiated tumours
- > 20mm in diameter
- > 4mm deep
- Immunosupression for whatever reason
