Common Skin Infections

FUNGAL DISEASES

Fungal infections are tremendously common in dermatological practice but even so we regularly joke that dermatologists often miss the diagnosis of tinea!!

Essentially two types of pathogens cause trouble on the skin:

• Yeasts e.g. candidiasis and seborrhoeic dermatitis.
• Moulds e.g. ringworm and fungal nail infections

Fungal infections

These can be considered as below:

• Superficial mycoses. Very common e.g. 20% people with tinea unguum/pedis 
• Deep mycosis. These are uncommon in the UK but more common in the tropics. 
• Systemic mycoses. Rare except in immunocompromised. Candida and malassezia species may be part of the normal flora but can cause disease in susceptible individuals

Candidal infections

There are several species, of which the commonest is candida albicans. These are usually superficial infections which thrive in hot sweaty areas. Typically they cause problems as below:

• vulvovaginal (thrush), oral, intertrigo, balanitis, napkin dermatitis
• risk factors: diabetes, pregnancy, immunosuppression 
• treat with topical antifungals, e.g. imidazole e.g. polyenes (e.g. nystatin); can treat with oral imidazoles (e.g. fluconazole) if necessary

Candidal intertrigo- note satellite lesions which can help with diagnosis

Candidal nail infection 

Clinically this presents with onycholysis, paronychia, dystrophy. May be seen in patients with Raynauds, Cushings, or in people who immerse the hands in water for prolonged periods. Treatment is with oral imidazoles, and advice regarding hand care and avoiding excess moisture.

Chronic paronychia – candida

 

Chronic mucocutaneous candidosis is rare familial condition which usually presents in childhood with recurrent oral candida and paronychia,

Clinical Tip- Candida and moulds tend to cause paronychia and a lot of inflammation in the periunguum

Amorolfine may be helpful for topical therapy of candida , although it is not very efficacious generally. Needs to be used for up to 12 months.

 

Malassezia yeast infections

Malassezia furfur is a normal skin flora, previously called pityrosporum species. It commonly presents with problems especially in atopics and immunosuppressed. There are various patterns of infection:

• Seborrhoeic dermatitis –  scaling of scalp and face ‘T’ zone-characteristically orange -red hue. Also caused napkin dermatitis.
• Pityriasis versicolor –see below
• Pityrosporum folliculitis – itchy, back and upper trunk in young males- see above.

 

Pityriasis versicolor

This is a very common rash usually seen in teenagers. Patients usually complain about it when they come back from a holiday and find that the rash is more noticeable when as it didn't tan! Typically we see coalescent orange- brown patches with surface scaling which can be helpful when making the diagnosis. Woods lamp shows pale yellow fluorescence though in reality one doesn't need to use this to make a diagnosis. Slight hyperkeratosis causes brownish colour in white skin, whereas the azaleic acid produced by the yeast causes hypopigmentation in dark skin. Hence the name- versicolor (variable colour).

Pityriasis versicolor – oval hyperpigmented patches

Treatment is with topical antifungals e.g. selenium sulphide (Selsun®) shampoo e.g. ketoconazole (Nizoral®) shampoo or cream e.g. terbinafine (Lamisil®). Occasionally I prescribe oral imidazoles e.g. itraconazole (NOT ORAL TERBINAFINE) if severe or resistant disease. Hypopigmentation persists for months and may become more obvious with a subsequent tan. Warn patients about this!!

Clinical tip: Flaking on scratching the lesions helps confirm the diagnosis