Onychomycosis is common condition of the toenails caused by a fungus. Usually it caused a deformity and discolouration of the nail plate, but a minor infection may just be a white discolouration or patch. It is not painful, but looks unsightly and can be embarrassing to the person with it to show their feet in public. The main risk factor for this is the moist environment inside shoes. The fungus loves that sort of environment. Treatment is difficult and prolonged as the fungus gets well established inside the nail plate, so any topical agent or internal drug as to penetrate that nail plate before it can work. The success rates of most treatments are disappointing due to the re-infection rate being so high. The reason for this is that most people with onychomycosis just put their feet right back into that dark moist environment that caused it in the first place. Whichever method of treatment that is used, you need to be patient and stick at it for the long haul and not expose the foot to the environment that caused it in the first place.
A mycetoma or madura foot is a severe fungal infection of the foot usually in tropical country. I just came across this reference to this condition that was apparently going to be used in a plot to kill Fidel Castro in Cuba!
See this video on mycetoma and this research on it.
Fungal infections of the toenails are unsightly and embarrassing. They cause the nail to lose its normal luster and become discolored. The treatment of these infections is difficult for a number of reasons. One reason is that it has to be treated as the nail grows out and is replaced with the new un-infected nail. This process can take 6 to 12 or more months. The environment inside a shoe is not exactly the most healthy place to put a foot and the infection can easily happen again. Most of the treatments for this involve using a topical medication or an oral medication and they need to be used for the entire 6 to 12 months. Recently the use of a laser is being explored (more) to destroy the fungal elements and then wait for the nail to grow out. This is looking promising, but more research is needed.
This is a growing problem that affects the navicular bone of the foot in young children. Its not clear what, but something appears to disrupt some blood supply to the bone and a type of necrosis sets in. The navicular is at the high point of the arch, so it is subjected to a lot of pressure and this may account for the problem. The most common age of onset is around 5 years and it may cause limping. The pain can usually be located to the navicular bone. Often on x-ray, the bone appears much more narrower than the unaffected side. Usually this needs to be placed in a walking cast (more) to protect the foot and its growing bones. After the cast is removed foot orthotics are often used (link) to further protect the weightbearing on the navicular bone.