I saw a patient quite recently and an interesting conversation developed. She highlighted that her reason for seeking a podiatrist’s consultation was due to her toenail concerns. The toenail may have had some trauma to it a number of years ago leading to some detachment. However, the whitening, along with the potential detachment, was her current concern. Upon probing, it was found that the nail was attached, and that the perceived whitening was a superficial fungus. The patient then indicated that at times, her thoughts extended to the fact that it was indicated, that Bob Marley died of cancer to the toe. For me looking at her toe, I was in no way led to believe that anything sinister was occurring. However, it was an indication of how the mind works, and the impact a toenail issue could potentially have on one’s well-being.
Based on this discussion, many thoughts triggered off in my mind, and I decided to highlight some of the more common toenail fungal infections with pictures, so some patients that I have not yet seen may be more at ease, although treating is important. Onychomycosis is one of the most common conditions a podiatrist sees. It is the umbrella term for a fungal infection. Onychomycosis is classified clinically as distal and lateral subungual onychomycosis (DLSO); superficial white onychomycosis (SWO); proximal subungual onychomycosis (PSO); candidal onychomycosis; and total dystrophic onychomycosis.
Distal and lateral subungual onychomycosis (DLSO)
This accounts for the majority of cases, and is almost always due to dermatophyte infection, (a pathogenic fungus that grows on skin,etc). It affects the hyponychium, often at the lateral edges initially, and spreads proximally along the nail bed, resulting in subungual hyperkeratosis (thickening), and onycholysis (separation from nail bed), although the nail plate is not initially affected. DLSO may be confined to one side of the nail, or may spread sideways to involve the whole of the nail bed, progressing relentlessly, until it reaches the posterior nail fold. Eventually, the nail plate becomes friable and may break up, often due to trauma; although nail destruction may be related to invasion of the plate by dermatophytes that have keratolytic properties. Examination of the surrounding skin will nearly always reveal evidence of tinea pedis (athlete’s foot). Toenail infection is an almost inevitable precursor of fingernail dermatophytosis, which has a similar clinical appearance, but the nail thickening is not as common.
This is also nearly always due to a dermatophyte infection. It is much less common than DLSO, and affects the surface of the nail plate, rather than the nail bed. Discolouration is white, rather than cream, and the surface of the nail plate is noticeably flaky. Onycholysis is not a common feature of SWO, and intercurrent foot infection is not as frequent as in DLSO.
Proximal subungual onychomycosis (PSO)
Without evidence of paronychia, PSO is an uncommon variety of dermatophyte infection often related to intercurrent disease. Immunosuppressed patients, notably those who are human immunodeficiency virus-positive, may present with this variety of dermatophyte infection; conditions such as peripheral vascular disease, and diabetes also may present in this way. Evidence of intercurrent disease (such as diabetes, etc), should therefore be considered in a patient with PSO.
Infection of the nail apparatus with Candida yeasts may present in one of four ways:
(i) chronic paronychia with secondary nail dystrophy;
(ii) distal nail infection;
(iii) chronic mucocutaneous candidiasis; and
(iv) secondary candidiasis.
Chronic paronychia of the fingernails generally only occurs in patients with wet occupations. Swelling of the posterior nail fold is secondary to chronic immersion in water, or possibly due to allergic reactions to some foods. The cuticle then becomes detached from the nail plate, losing its water-tight properties. Infection and inflammation in the area of the nail matrix eventually lead to a proximal nail dystrophy.
Distal nail infection with Candida yeasts is uncommon, and virtually all patients have Raynaud’s phenomenon or some other form of vascular insufficiency. It is unclear whether the underlying vascular problem gives rise to onycholysis as the initial event, or whether yeast infection causes the onycholysis. Although candidal onychomycosis cannot be clinically differentiated from DLSO with certainty, the absence of toenail involvement, and typically a lesser degree of subungual hyperkeratosis, are helpful diagnostic features.
Chronic mucocutaneous candidiasis is multifactored, leading to diminished cell-mediated immunity. Clinical signs vary with the severity of immunosuppression, but in more severe cases, gross thickening of the nails occurs. The mucous membranes are almost always involved in such cases. Secondary candidal onychomycosis occurs in other diseases of the nail apparatus, most notably psoriasis.
Any of the above varieties of onychomycosis may eventually progress to total nail dystrophy where the nail plate is almost completely destroyed.
Treatment needs to be administered long-term. However, enough time must elapse for the nail to grow out completely, before such treatment can be designated as successful. Toenails take around 12 months to grow out. Both topical and oral agents are available for the treatment of fungal nail infection.
Your feet mirror your general health . . . cherish them!