Dermatophyte fungi ( ringworm) Nondermatophyte fungi Yeasts cause about 5 % of infections.Distal and lateral subungal ( most common ) Proximal subungal White or Black superficial Midplate type Total dystrophic.
Dermatophyte fungal infection responsible for about 90 % of cases of onychomycosis.Begins with invasion of stratum corneum of the hyponychiumn in distal nail bed whitish to brownish-yellow opacification of the distal edge of nail infection spreads proximally up the nail bed to ventral nail plate subungal keratosis hyperproliferation of nail bed ►progressive nail dystrophy
Dermatophytes-Trichophyton.rubrum- responsible for > 70 % infections T.mentagrophytes about 20 % T. interdigitale T.tonsurans E.floccosum.
Yeasts-Majority caused by Candida albicans- occurs in conjunction with chronic muco-cutaneous candidiasis True infection with yeasts are rare and more↑ likely to affect the finger nail or nail folds
NON-DERMATOPHYTE ( Rare ) Usually follow nail trauma , immunosuppression or underlying dermatophyte infection Discuss management with microbiologist or dermatologist Diagnosis requires positive direct microscopy , isolation of organism in pure culture and ideally on repeated ocassions.Acremonium Aspergillus Fusarium Onychocola canadensis Scopulariopsis brevicaulis ( most common) Scytalidium dimidiatum
risk factors-Diabetes ( 3 times ↑ likely ) Age and ↑ frequently in men Hyperhidrosis Genetics Psoriasis immunodeficiency- eg HIV ( T cell ct 400) Smoking Peripheral arterial disease ↑ participation in physical activity Exposure to wet work Ill fitting shoes Commercial swimming pools Working with chemicals Walking barefoot Nail biting Occupation ( athletes )
Differential-Psoriasis Lichen planus Trauma Eczema Viral warts Yellow nail syndrome Lamellar onychoschizia Periungual squamous cell carcinoma / Bowen’s disease Malignant melanoma Myxoid cyst
Advice about treatment-Treatment cure rates approx 60-80 % Drugs need to be taken for several months or longer for resistant nails May not restore the nail completely Serious side effects are rare
Sample collection-Wipe off any treatment creams before sampling Send most proximal part of diseased nail- with chiropody scissors Also sample debri from under the diseased part of nail In superficial infections scrape surface of the diseased nail plate with scalpel blade ►►Samples should be kept at room temp and collected into folded dark paper sqaures (secure with clip and place in a plastic bag ) Commercial collecting kits available- Mycotrans , Dermpak
Terbinafine-1st line 6 weeks to 3 months in fingernail 3-6 months intoe nail Improvement expected end of 2 months ( fingernail ) and 3 months (toe nail ).Keratophilic medication- both fungistatic and fungicidal Inhibits fungal enzyme (squalene epoxidase ) → accumulation of sterol squalene →toxic to organism Reduces ergosterol → prevents synthesis of fungal cell membrane.Rash Dec’d appetite GI upset Headache Arthralgia , Myalgia Hepatotoxicity -rare ( jaundice , cholestasis and hepatitis ) Taste disturbance ( uncommon ).Severe chronic or active liver dis Severe renal impairment Pregnant Breastfeeding Psoriasis ( ↑ risk exacerbation ) Autoimmune diseases -risk of lupus erythematosus like effect Renal impiarment ( use 1/2 normal dose if GFR < 50 ) and no alternative Discontinue usage if LFTs are elevated Terbinafine is a CYP2D6 inhibitor- would interact with drugs metabolised by CYP2D6 ( eg Amitriptyline , impipramine , Nortriptyline , Desipramine , Beta blockers , SSRIs as Paroxetine , MAO inhibitors and some antiarrythmics as Flecainide ) Also check individually interactions with liver enzyme inducers and inhibitors
itraconazole-Pulsed therapy → 200 mg bd for 1 week with subsequent doses repeated after 21 days Fingernail → two and Toenail → atleast three Consider monitoring LFTs ( eg monthly )Blocks fungal P450 enzymes and interferes with ergosterol synthesis ↑↑ cellular permeability causing leakage of cellular contents.GI SEs common Serious adverse effects rare Rare reports of liver toxicity ( consider monitoring LFTs to exclude liver disease ) Check LFTs if anorexia , nausea , vomiting , fatigue , abdominal pain or darkening of the urine occurs
↑ liver enzymes (record baseline and monitor regularly) If H/O previous liver toxicity with other drugs Active liver disease Heart failure or h/o heart failure -can precipitate HF ( negative inotropic effect ) Concomitant usage with -Astemizole (antihistamine-already withdrawn from some countries as US ) , Pimozide ( antipsychotic ) , Quinidine or terfaindine- ↑ arrythmia risk ↑ risk myopathy with statin Metabolized via cytochrome p450 and interacts with number of liver enzyme inducing drugs and liver enzyme inhibitors
References ; Further reading Medicine compendium www.medicine.org.uk CKS Fungal nail infection accessed via http://cks.nice.org.uk/fungal-nail-infection Fungal nail infection : diagnosis and management BMJ 2014 ; 348 : g1800 Onychomycosis : Current Trends in Diagnosis and Treatment Dyanne P.Westerberg et al Am Fan Phyician 2013 Dec 1;88 (11) : 762-770 Fungal Nail Infections ( Onychomycoses ) : Diagnosis , Lab Investigations and Treatment Quick Reference Guide for Primary Care Aneurin Bevan Health Board British Association of Dermatologists’ guidelines for the management of onychomycosis 2014 M.Ameen et al British Journal of Dermatology July 2014 Onychomycosis : Diagnosis and management Archana Singal, Deepshikha Khanna ; Indian Journal of Dermatology Venereology and Leprology 2011 Vol 77 Issue 6 Page : 659-672