Common Skin Infections

DISEASES CAUSED BY MOULDS

Moulds represent a large group of organisms, most of which are non-pathogenic. Human disease is caused by both dermatophytes and the non-dermatophytes 

Dermatophytes = ringworm. There are 3 groups: trichophyton, microsporum and epidermophyton. 

Non-dermatophytes = many types of less importance. 

 

Presentation

These are classified according to body part affected e.g. Tinea corporis, tinea capitis, tinea cruris, tinea pedis, tinea unguium. Infection may cross anatomical boundaries, and features are related to the degree of inflammation, which in turn depends on the dermatophyte species e.g. animal species more inflammatory than ‘human’ species.

Tinea cruris – note the well-defined, inflammatory, red edge

 

Top Tip: Tinea in feet may be a portal of entry for cellulitis

 

Key features of fungal skin infection

• Well defined lesions that may have a raised edge. 
• Single or unilateral. 
• May have some vesicles or pustules. 
• May look psoriasiform on legs and feet. 
• Differentials include discoid eczema, pityriasis rosea with herald patch, lichen simplex, erythrasma. 
• May be modified by steroids i.e. tinea incognito 

Diagnosis is by skin scrapings for mycological culture or if available with KOH preparations in the clinic.

Treatment- small areas may be treated with topical terbinafine or ketoconazole for 2-4 weeks. In severe or widespread infection or tinea manuum use oral terbinafine or oral itraconazole for 2-4 weeks or longer for toenails - 3 months.Oral itraconazole can be used as a pulsed regime .

Tinea corporis on the arm – note the well-defined leading edge

 

Performing skin scrapings 

• Disposable scalpel or blade which is held perpendicular to skin surface 
• Use Firm strokes over edge of lesion without lacerating skin 
• Scrape onto black paper (easier to see). 
• Fold and seal for transport.

Dermapak envelope for transporting skin scrapings, nail clippings or hair for mycological analysis

Tinea capitis 

This is a condition which is more common in children than adults and is much more common in Afro-Caribbean children. There are two common patterns, but it may be very varied in its presentation, from subtle scaling to broken 'black-dot' hairs.

It may cause a patchy rather moth-eaten alopecia –with well defined round areas of hair loss, minimal scale and broken hairs

Tinea capitis – patchy alopecia and scale

 

Tips: Hair plucks as well as scrapings should be taken. It is painless to extract hairs. 

 

Kerion occurs due to exaggerated host response to presence of mould. Clinically we see a boggy inflamed mass, with pus, matted loose hair & scale crust and sometime associated with lymphadenopathy.

 

Tip: do not let the surgeons Incise and drain this- it responds to medical treatment, often with full hair regrowth (surprisingly).

Kerion – boggy inflammatory mass with alopecia

 

Investigation - with scrapings & plucked hair. Woods lamp limited value – only picks up some species.

Treatment -

• griseofulvin 10-20 mg/kg for 2 months has historically been used as first line but more recently many clinicians are using terbinafine half adult dose for 4 weeks as first line therapy.  Ketoconazole shampoo should be used for both patient and unaffected siblings and other family members as fomite spread is a major issue with tinea capitis. Children should not need to be excluded from school for this, and it is important to warn of the possibility of an Id reaction, which occurs when treatment of inflamed dermatophyte e.g. kerion results in distant reaction. There are 2 patterns, namely a pompholyx like reaction and follicular papules on trunk and limbs. This resolves with treatment of dermatophyte infection.

 

Tinea unguium 

There is often associated tinea pedis or tinea manuum, therefore take skin scraping as well as nail clippings. There may sometimes just be a couple of nails involved.

 

Tip: If all nails are affected it is less likely to be tinea and more likely to be primary nail pathology such as psoriasis

 

There 3 types typically described.

1. distal and lateral subungual onychomycosis (DLSO). This is the most common pattern with yellow/brown/black colour and soft subungual hyperkeratosis. It spreads proximally and other nails may be sub clinically infected. It may cause discomfort.

Extensive Tinea Unguium toe nails

 

2. white superficial onychomycosis (WSO). This produces powdery white discoloration of the distal nail and is more common in HIV disease but is also found in health adults and children.

3. proximal subungual onychomycosis (PSO) rare except in HIV. Proximal nailfold infection with rapid invasion and white nail without thickening.

 

Tip: It is worth sending clippings and subungual debris for microbiology. When moulds are involved one sees periungual inflammation

Treatment: terbinafine 250 mg daily for 6 weeks in fingernails and 12 weeks in toenails, or itraconazole pulse 400 mg/day (as 200 mg bd) for 1 week per month for 3-6 months or as 200 mg daily for 12 weeks. It has a long half life and may persist in the nail plate for up to 6 months and may cause taste disturbance which can be permanent. It has minimal drug interactions. It is better for diabetic patients and those with HIV.

Itraconazole is fungistatic but is more broad spectrum and reasonably good for candida and moulds. Pulse therapy is useful as it decreases the risk of toxicity. Monitor LFT if long term or other hepatotoxic drugs.

If treatment is unsuccessful, reconsider diagnosis e.g. trauma, psoriasis, LP, eczema.

Elderly and patients with e.g. psoriatic nails are harder to treat.

Dermatol Ther. 2017 Jan 18. doi: 10.1111/dth.12457. This study looked at efficacy and tolerability of amorolfine 5% nail lacquer in combination with systemic antifungal agents for onychomycosis:

The efficacy and safety of amorolfine 5% nail lacquer in combination with systemic antifungal agents in the treatment of the onychomycosis were evaluated. According to meta-analysis, combination treatment of amorolfine 5% nail lacquer and systemic antifungals can result in higher percentage of complete clearance of onychomycosis. It showed that the experimental combination group was more effective than monotherapy of the systemic antifungals [OR (odds ratio) = 1.97, 95%CI (95% confidence interval) = 1.44-2.69], and no more adverse events happened with the addition of amorolfine 5% nail lacquer (OR = .96, 95%CI = .56-1.63, p = .95). This effect strengthens the fact that amorolfine 5% nail lacquer in combination with systemic antifungal agents was better than the monotherapy of systemic antifungals like itraconazole and terbinafine.

 

Non-dermatophyte mould infections

These are relatively uncommon in the UK but more common in some tropical countries, USA and the Mediterranean region. e.g. Scytalidium spp:

• Causes Ringworm like infections  

• Affects palms, soles and webspaces 

• Nails are frequently involved, including onychomycosis 

• It is difficult to treat with usual oral antifungals 

• It may require nail removal. 

• Whitfield’s ointment can be useful for scaling sole lesions

Other fungal infections 

The rest of the fungal infections are mostly subcutaneous or systemic and tend to occur in Indian subcontinent, Middle-East and Africa

Subcutaneous mycoses

These are infections caused by fungi which are directly inoculated into the dermis or subcutaneous tissue through a penetrating injury. Mainly seen in the tropics.

Sporotrichosis

Fungus is usually introduced by trauma, e.g. by a thorn or splinter, usually into the upper limb where a nodule or pustule forms and via lymphangitic spread a chain of nodules develops. Whilst it may resolve spontaneously it is usually treated with Itraconazole.

 

Systemic mycoses

These are fungal infections that involve deep structures and can spread, usually via the bloodstream, to a site distant from the original focus of infection. 

Cryptococcus yeast in HIV infection

• Often resembles molluscum contagiosum on the skin
• Systemic involvement is usual – CNS and lungs 
• Needs amphotericin B + imidazoles