Study of various types of Infectious Diseases

So tinea infections are infections by fungi known as dermatophytes,  and they come from the genus trichophyton or  epidermophyton. Here are the images of those  trichophyton and epidermophyton fungi.

Now the  pathophysiology of tinea infections involves the fungi metabolizing the protein keratin in our skin, nails and hair - this is how they actually present  and why they actually look the way they do because  fungi metabolize keratin it leads to lesions,  scarring, brittleness of the nails, and dryness that  type of clinical picture.  

Names of Infection according to location on

body 

Now, the tinea infections  are actually named depending on body location.  If there is any infection on the trunk, it's  known as tinea corporis.

If it's an infection on the  feet, it's tinea pedis, if it's an infection on the  head it's tinea capitis. If it's an infection of  the groin, it is tinea curries, and if it's an infection  of the nail, it is known as tinea unguium.  

So the first one we're talking  about is tinea pedis, otherwise known as athlete's foot. 

Tinea Pedis: 

This is probably a very common one that many  people know about and probably have had. It is the  most common dermatophyte infection and it presents  in a few different clinical presentations.  

Interdigital tinea pedis: 

The first one is the most common presentation - it is  interdigital tinea pedis. This is the most  common type - it's itchy (pruritic) and it's scaly. So we can see  in this image here again it's very scaly looking.   

Hyperkeratosis and vesiculobullous  eruption: 

Another presentation is a hyperkeratosis. It's erythematous but mostly involves the soles of the feet and the other one is vesiculobullous  eruption, and again this can be pruritic, so  itchy, but can also be very painful and it happens on the  medial foot.

So interdigital is between the toes. Hyperkeratotic  occurs on the soles of the  feet and then the vesiculobullous eruption occurs  on the medial foot.  

Tinea corporis: 

Tinea corporis is also known as ringworm, and again this one  affects the trunk. So when we say trunk, it really  basically means anywhere on the body except the  hands, the feet, the grown or the face. 

Appearance: 

This  one is also pruritic (itchy)  it is circular/oval in shape and it too is  also a scaling patch or plaque. So it's a patch or  plaque. A patch is a flat surface or flat lesion  that's greater than one centimeter and a plaque is  a raised lesion greater than one centimeter and  it spreads centrifugally. 

We're going to talk about is tinea capitis. Tinea  capitis is a fungal infection of the head and an  easy way to remember this is capitis, "cap", so you  can think of the cap or the top of your head or  you can put a baseball "cap" on  your head. So this is how you can remember tinea  capitis is an infection of the head.  

Appearance and Impacts: 

And this leads  hair loss and it too is also pruritic (itchy)  and scaling and this one is actually more  related to a direct contact transmission.

So if  one person has tinea capitis, you can actually  have a transmission from that person to another  individual so that they can have tinea capitis as well. So again, you see this patchy hair loss with  this characteristic scaling appearance.  

Tinea cruris is a fungal infection  of the groin area, and this is commonly known as  jock itch. This affects men more than women,  and what happens generally in this presentation  is that it begins on the medial thigh (so the  inner sides of the thighs), and it's also spread  centrifugally, so it spreads from its center  outwards.  

Factors: 

It's also erythematous and elevated. So it becomes well demarcated because of this,  and it has associated factors involved:  

one  is excessive sweating - so a lot of times this is  why it's a jock itch sometimes in men or someone  that's very active where they can become  very sweaty in that area and it can lead to this  jock itch.

Other associated factors include diabetes  and obesity and also immunodeficiency, so all  these can relate to getting jock itch or recurrent  jock itch or recurrent tinea cruris.  

This one is basically a fungal infection of the  nail.  It's also called  onychomycosis. It is basically a crumbling, brittle  nail just because the fungi are actually digesting  away the nail itself. It leads to a yellowish,  opaque nail and if you're to take a look  underneath the nail you get some unusual hyperkeratotic debris.  

So now that we've seen a variety  of clinical presentations of tinea infections, how  are they diagnosed? The diagnosis involves  doing a KOH preparation of skin scrapings and  what you would see is you would visualize segmented hyphae.  

Treatments: 

So once we've made the diagnosis, how do we treat it?   

Treatment typically involves topical antifungals  or medications with "-azole" at the end of their name. With the "-azole" suffix, you can think of medications  like fluconazole and another one might be butenafine.

So majority of cases of  tinea infections are treated with  topical antifungals but there are two special  cases I want you to think about and I'll tell  you a way to remember them in a moment.  

Special cases: 

So the two  special cases are tinea capitis  we're going to typically use  terbinafine or griseofulvin. And the second one is  tinea unguium   and we're going to generally either use an oral  antifungal or efinaconazole for a  very long period of time about 48 weeks .

We've been moving away from oral  antifungal just because of some liver toxicity  issues, so we're more going toward efinaconazole,  which is also a topical treatment but it's a more  special topical treatment for tinea unguium.