if you want to learn everything that you need to know about dermatology for the usmle then you have came to the right place so let's begin diseases that cause a rash on the palms and souls is an extremely high topic for the usmle one such disease is rocky mountain spotty fever we can remember the other causes of rash on palms and souls with this trick well it's more like tricks so here's a mnemonic t toxic shock syndrome are rocky mountain spotted fever i infected endocarditis c coxsackie a k kawasaki and the first as staff scottish skin syndrome and the last s secondary syphilis recall that in infective endocarditis these patients can have janeway lesions on their palms for coccike a i want you to leave in the comment section below what disease an infection with the kawksaki a virus can lead to but to be honest all of these diseases here are extremely high yield you can probably think about them like the tricks that the usmle have but let's go here we have two pictures showing erysipelas and cellulitis do you know which is which if not then that's totally fine that's why i'm here or better that's why you're here watching this video so the first picture shows cellulitis and the second picture shows erythropylus erasapellus and cellulitis can present similarly and of course anything with overlapping features or that are really the same examiners love to test them because you can confuse them however i'm going to show you how not to do that so for irisa palace if you take a good look at this picture you can see that it has raised sharp borders and a very intense erythema while that is not the case in cellulitis in cellulitis the borders are indistinct the erythema is not as intense and the borders are not sharp it's important to know that cellulitis is a skin infection of the deep dermis and subcutaneous fat however erysipelas is more of a superficial skin disorder now let's look at a image so that you can remember this fact so how i remember it is with this image of the earth's core right so the c from cellulitis and the c for core so it lets me know that just like with the earth's core it's very deep and cellulitis is deep as well and for palace it is the opposite so i hope that this image will help you as much as it has helped me now here we have erythema nodosum and erythema multiforme erythema nodosum is a delayed hypersensitivity reaction it's usually tender erythematous nodules most often on the shins as you can see in this picture however in erythema multiforme we describe these lesions as being target lesions however the high yield fact is that these two skin conditions have very high yield associations let's take a look at what they are erythema nadosum is associated with inflammatory bowel disease sarcoidosis penicillins sulfonamides and even oral contraceptives however erythema multiforme is associated with herpes simplex virus extremely high yield so basically anything that you see in green during this entire video just think of it as green it's money it's money for the usmle so know it well now i can probably bet that absolutely everyone has seen this picture so let's review this topic this picture is showing erythema chronicle migrants and this is the key dermatological finding in lyme disease so remember this very high in fact lyme disease is treated with amoxicillin in patients less than eight years old however doxycycline is used in patients older than 8 years old recall that doxycycline is a tetracycline and they can cause teeth discoloration so that's the reason why amoxicillin is given in patients less than eight years old however there is another extremely high yield fact about tetracyclines so let's say we have a patient she has a lyme disease she was given doxycycline for her treatment she's fine um one day she goes for a walk or run and then she is very very sunburned why is that well it's because tetracycline can cause photosensitivity we can remember the drugs that can cause photosensitivity with the mnemonic set for a photo sat stands for sulfonamides amitriptyline and tetracyclines so i know we just talked about the patient being sunburned but this picture on the other hand is definitely not a sunburn this is redman syndrome so how we can differentiate between a sunburn and redman syndrome is of course the patient's history what drugs they took because different drugs cause different reactions and in sunburnt patients they usually have a tan line but that's not seen in redmond syndrome so the drugs that most commonly cause redman syndrome are vancomycin and ciprofloxacin if you made it this far into the video and you are enjoying this extremely high yield content be sure to power up that like button and hit subscribe now here we have three high-yield skin findings porphyria cutaneotarto lycan planus and cryoglobulinemic vasculitis but my question for you is what disease are all these different skin conditions associated with if you said hepatitis c then you are correct so it's very important that if you see any of these skin findings you have to screen for hepatitis c especially if that patient has a history of iv drug use so proferas are disorders of heme synthesis but the most common one is porphyria catania tardo and it can be triggered by the ingestion of estrogens or ethanol and of course it's associated with hepatitis c these patients may have fragile skin photosensitivity and even blisters lab work can reveal elevated plasma or urinary porphyrin levels and in order to treat porphyrias we use phlebotomy or hydroxychloroquine now let's focus a bit on lichen plaines so that includes the five p's purple poetic polygonal papules or plaques there's also drug induced lichen plainness that's associated with a number of drugs some of them being ace inhibitors thiazides beta blockers or hydroxychloroquine now here we have a classic image of herpes zoster this is a painful reactivation of the varicella zoster virus and it causes a vesicular rash in a dermatomal distribution that is extremely extremely high yield so in order for us to decrease the duration of the disease or the incidence of post-herpetic neurology we give the patient a cyclovir two of the biggest predisposing factors for shingles include the patient's age and if they are immunocompromised and now we have that classic rash seen in henoch online per pero so this is typically seen on the buttocks or thighs of children who have henox online per purl so we can remember some of the key features of this disorder with the letters hsb h he material s small child like us small children are usually affected and p palpable per plural if you want to see a high yield review of hanok shanghai purpura ig nephropathy and post-ship glomerulonephritis be sure to check out the link in the description below patients with celiac disease can develop this skin finding called dermatitis herpetiformis dermatitis herpetiformis is an autoimmune reaction due to the ingestion of gluten in order to treat this the first line is of course a gluten-free diet however if that doesn't work then we have to use dapsone but let's say a patient takes napstone but then they develop hyperbilirubinemia and jaundice what is the most likely cause of that and that is a dabstone induced hemolytic anemia this occurs in patients who have g6pd deficiency guys if you like the high yield facts be sure to power up that like button smash that like button make that like button turn blue and of course subscribe to the channel now let's continue now this is teeny birthday color so you will see a question that says there is this young woman she went sunbathing or went to the beach but after that she noticed these hypo pigmented macules that is classic classic presentation of tineo versicolor that's why i have this little image here of someone like sunbathing or just relaxing in the sun so tinea particular is a superficial fungal skin infection if you look under microscopy of like skin scrapings of patients with this disorder you'll notice something called spaghetti and meatballs appearance and in order to treat these patients we use topical selenium sulfide ketoconazole or turbinophen hiv also increases the risk of tinea versicolor so hiv is a very very very prominent in dermatology and especially in this lecture as it pertains to the usmle a lot of cases you will hear something like hey this person has um a very diffused skin condition more likely it has an association with hiv or hiv would increase the likelihood of developing said skin condition so just keep that in mind and let's move on pitorises rosie so this usually starts with something called the herald patch and that is what that arrow is highlighting after the development of the hurl patch you can see development of clusters of small oval-like lesions they are oriented in a christmas tree that's why you see that lovely christmas tree right there so you can remember this association however before the patients develop any skin findings they can have a viral program so they kind of feel sick like maybe have like a fever runny nose or something like that and in order for us to treat these patients we of course provide them with reassurance and also because patriotis reside can be very very itchy we can give them antihistamines or some topical steroids to relieve that and here we have vitiligo which is an autoimmune disease that occurs due to melanocyte destruction and that results in a deep pigmentation so it's considered as a depigmentation disorder it's very important that you remember that it is an autoimmune disorder because that means it can be associated with other autoimmune disorders like type 1 diabetes hashimoto's thyroiditis or alopecia areata so yeah just keep that in mind very very high yield let's move on so for vitiligo we're kind of used to seeing the typical image like i showed you before however there is a subset of vitiligo that can only affect the genital or oral mucosal and this picture showing you an example of the oral type of vitiligo now here we see some hypo pigmented macules also known as ash leaf spots and these can be present at birth and are most common on the lower extremities and on the trunk but my question for you is what condition is this associated with so you don't forget i've asked you two questions so far the first one being what disease or condition can infection with a virus lead to and what condition is the ashley spots associated with be sure to comment them down below and let me know liken simplex chronicus this is a neural dermatitis so it has the features of thickened excoriated plaques and this is caused by persistent itching and rubbing it's very high yield that you know it's associated with anxiety disorders so it typically occurs in areas that are very easy to reach this is hydroadenitis super tavo and it's probably a very mild version of what you may see in practice questions or on exam day because this condition can lead to sinus tract formation or even scarring as well it typically arises in places where there are folds or creases like the axilla or the inguinal area and this occurs due to an occlusion or inflammation of the follicular pylor sebaceous units very high yield remember that um the risk factors include a history of smoking diabetes mellitus chronic mechanical stress of the skin such as excessive friction or pressure and obesity so one of the treatment options for hydroadenitis superitivo is weight loss now this candidal infection also occurs in the folds as well and it is usually moist and macerated okay now onto scabies so patients that have scabies it is very very very itchy and it's characterized by like these um red papules and burrows and you can see them in the axilla the genitalia but of course the classic thing that we're used to is the inter-digital web spaces and it is also a type 4 hypersensitivity reaction to mites feces and eggs so the first line treatment for this is permethrin or oral ivermectin i also need to be sure to clean bedding and clothing or place them in a bag for like more than three days because the mice can survive up to that long and now we have the us emily's favorite tiniest tinea capitus tini corporis and tinipedis these are very common in very classic pictures so be sure to look at them and know them well a key thing to remember about all of these conditions is that they are all treated with topical antifungals except tinea capitis that is usually treated with oral crystal faulvine so in the pediatric population these two conditions can be easily confused but here's a simplified way so that you can remember them so in candida diaper dermatitis the skin folds are involved that's because candida does not care they don't obey any boundaries they go wherever they want to go so the skin falls are involved however for irritant diaper dermatitis the skin falls are not involved in order to treat candida diaper dermatitis of course we use antifungals while we use barrier ointments for the treatment of irritant diaper dermatitis and let's stick with the pediatric population a bit more and look at these two conditions congenital dermal melanocytosis and congenital melanocytic nevas i put them side to side because they both have congenital and they melano something so they can be kind of confused so i put them here to highlight the differences with their names and you have visual representation so you don't confuse them but you may know congenital dermal melanocytosis more commonly as mongolian spots mongolian spots are commonly found in african asian and hispanic infants and they look like blue gray macules and they're more common on the sacrum and the buttocks so sometimes you have a case or a question where you know the parent comes in they're like they have this rash they're freaking out you have to know that no treatment is required because it's self-limiting and it goes away or you might have a question and in the option they're like called child protective services and it's basically trying to steer you towards thinking that it's a case of child abuse so it's very important to look at this picture and know it well mongolian spots or congenital dermal melanocytosis however for the congenital nevas it's hyper pigmented patches with a very very dense patch of hair follicles as well alopecia areata is another autoimmune condition just like vitiligo that we talked about before so of course it can be associated with other autoimmune diseases so it's characterized by a painless patchy hair loss there's no erythema no scarring and no scaling in order to treat alopecia areata we can use topical or intralusional steroids okay now here we have a kentosis naga cans this is described as a hyper pigmented or velvety plaques on the axilla neck or groin it's extremely high yield that you know is associated with insulin resistance states like the ones mentioned here diabetes mellitus or picas however in older patients if you see acanthosis nigricans in older patients it can be associated with a gi malignancy and here we have pseudofolliculitis this is most common in black men and if you just look at this picture and know it it's an easy gaming question so pseudofolliculitis more common in black men and the treatment for this is usually to stop shaving or use a different shaving technique now this slide is so so so high yield so let's master this so this is psoriasis psoriasis has different dermal presentations they typically have the silvery plaques on like extensor surfaces they can also have nail pitting as you can see with the green arrow or even eye changes such as conjunctivitis or uveitis represented by the red arrow now this phenomenon here that's basically the worsening of psoriasis when there is a local skin trauma so even if like with intense itching it can cause that type of reaction one way that examiners can test you is by saying oh this patient has the silvery plaques what other clinical findings can be present in the patient and you have to know all these other findings so if you know them then that can be a quick and easy question the treatment options for psoriasis is also interesting because this includes topical hypotensive steroids or vitamin d derivatives but if the psoriasis is more severe then we have to move on to systemic treatment such as methotrexate so the third time is a charm so please be sure to like this video so that i know you're enjoying the content that i'm creating now in this picture we're seeing all these different conditions on cheeks basically cheat conditions so what are they well let's look at the top two conditions first and these are rosacea and sle so it's very important that you look at these pictures and realize how they are different the key finding is in that sle you have sparing of the nasolabial folds however in this type of rosacea the nasolabial folds are involved so that's a high-yield way of distinguishing them and this is melasma so this is typically described as a hyperpigmentation on the cheeks and it's associated with states with elevated estrogen like in patients that take birth control or in women that are pregnant so they can describe it as like a pregnancy mask and like oh my gosh what should we do to treat this patient so if that patient is pregnant and they have this quote-unquote mask then we just have to wait until the mother gives birth and then it can go away after that and this picture here is showing erythema infection so my third question for you is what virus can cause this skin finding leave it in the comments below this is the last question i think so there's one two three let me know what the answers are for all the questions that i asked and now on to our favorite gimme question which is impetigo so if we see this picture or hear the classic description of honey crusty lesions around the mouth or a honey crusted rash then we automatically think about impetigo and impetigo can lead to post-strip glomerular nephritis and again if you want to see a high-yield video comparing paulship glomerulonephritis ij nephropathy and henakshanan per be sure to check the description of this video okay now here we have a dermatofibroma which is a non-tender nodule what's very high yield is that if you pinch this nodule or this dermatophyte bromo it can cause a dimple as you can see here in this red circle okay so molluscum contagiosum this is caused by the pox virus if patients have this but it is very widespread then what we have to do is an hiv test and this picture right here is pyrodermal gangrenosum it's characterized as a rapidly progressive painful ulcer and of course you can see the purulent base it's most commonly associated with inflammatory bowel disease so if you have a question where you see this picture or there is a description of pioderma gangrenosum and they ask you the next best step if you see colonoscopy choose that as the answer and here we have libido reticularis that has a mottled vascular pattern and it's described as being like a lacy pattern or a net like pattern and here we have acne so in mild acne we can use topical retinoids if that doesn't work we can add a topical antimicrobial for moderate acne we can use oral antibiotics and for very severe acne we can use isotretinoin so it's basically like a step up like from topical retinoids to topical antimicrobials to oral then to isotretinoin so what's high yield about this topic of acne is the isotretinoin so you'd have a patient come in and she wants to start this medication or she is on this medication they're basically seen if you know the protocol which basically involves having two forms of contraception and doing regular pregnancy tests so if a patient comes in and they have very bad acne you're doing all the steps and it's just not going away one thing for you to consider is a steroid induced acne so for certain induced acne it does not respond to regular acne treatment the best treatment for these patients include stopping the steroid and now here we have the skin findings of dermatomyositis so these skin findings include gotchans papules as you can see on the dorsum of her hands right there or a heliocho brush which is seen on the eyelids and the last one is the shawl sign it's important to note that dermatomyositis can be associated with polymyositis where these patients have a weakness of proximal muscles like the muscles of the hip girdle or shoulder here are the three main types of dermatitis tested on the us emily do you know which is which if not let's go to the next slide so let's focus on seborrheic dermatitis first so how i identify that one is because of the greasy appearance and it's usually the crater cap seen in infants or neonates while for contact dermatitis it has vesicles in the exposed area of the skin where they were exposed to the irritant for atopic dermatitis it's not so cotton dry so i basically just identify that one as like a process of elimination now you might be wondering why those check marks and x's are there well that's because i'm trying to highlight that atopic dermatitis and contact dermatitis are treated with topical emollients while seborrhoeic dermatitis is not treated with topical emollients it is treated with selenium sulfide shampoo just like with tinea versicolor it's very high yield that you know that cerebral dermatitis has associations with hiv and parkinson's and here we have keratosis pylaris so this is more common on the posterior forearm and is described as a roughened texture of the skin so we usually treat it with cards analytics like salicylic acid coretto panthoma so this is a nodule with a keratin plug in the center of it okay now this is so high yield here we see pictures of a patient with lymphedema who then goes on to develop angiosarcoma recall that we can see chronic lymphedema in breast cancer survivors however these patients can then go on to develop angiosarcoma which is a malignant tumor it's derived from the lining of blood vessels and lymphatics the strongest risk factor for the development of angiosarcoma is localized radiation therapy guys you're like 30 minutes into this video so might as well you just smash the like button power it up make it turn blue so that i know you're enjoying this content now let's continue so we are going to talk about skin cancer the number one risk factor for skin cancer is accumulated exposure to the sun so of course we have to talk about sun protection avoiding the sun is the best form of photo protection but if you do go outside it's recommended that you use sunscreen with at least 30 spf or greater and you apply that 15 to 30 minutes prior to going outside however you have to reapply the sunscreen every two hours and if you go swimming you have to reapply it immediately after you swim dark colors long sleeves and broad brim hats like in this picture are recommended to block sun exposure here we have a picture of a melanoma let's say we have a patient that has moles but there's this one mole that just does not look right and we call it the ugly duckling sign if you see a patient with moles but there's one that just looks very different it's it bleeds it itches then we should be very suspicious of a melanoma other features that are suggestive of a melanoma can be remembered with a b c d e asymmetry border irregularities color variation diameter greater than six millimeters and evolution in shape size or color so if a lesion has any one of these then we have to do an excisional biopsy so there are three main subtypes of melanomas the nodular type has the worst prognosis the acryl type is more common in african americans also melanomas are usually commonly associated with what's called the breast flows depth however that has changed to the ajcc depth but i'm not sure if that is being reflected in the usmle exams currently so just be aware of those depths the breast cell depth and the ajcc depth it basically lets you know the prognosis of the melanoma so basal cell carcinoma that is the most common skin cancer in the general population basal cell carcinoma can have this pearly like appearance and it's very important that if basal cell carcinoma is on more delicate or sensitive areas such as the face to excise this or remove this lesion we use the moss surgery so that's basically where thin layers are removed and that is the procedure that is preferred for very delicate sensitive areas squamous cell carcinoma on the other hand that looks a bit different as you can see here it can arise in chronically scarred inflamed or wounded skin so if a squamous cell carcinoma arises from a burn this is called a margins ulcer if a squamous cell carcinoma is biopsied then we may hear a description of keratin pearls okay so this lovely picture right here this is showing you which cancer affects which parts of the lip so squamous cell carcinoma most commonly affects the lower lip while basal cell carcinoma affects the upper lip more commonly i remember this by using bs so b for the upper lip and s for the lower lip and here we have seborrheic keratosis so this is described as having a stuck on appearance it's very important that if you see a patient with many of these then this can be indicative of a gi malignancy a nekolsky sign is when there is a light pressure or friction of the skin and that leads to the upper or more superficial layer of the skin to slip off so that is a nikolski sign this is positive in patients with stevens-johnson syndrome or t-e-n these conditions are precipitated by the use of drugs so we can distinguish them by the percent of body surface as affected so less than 10 percent that's stephen johnson syndrome 10 to 30 percent that's a mix and greater than 30 that is t t-e-n it's very important to note that these patients require aggressive fluid support and wound care in their management and here we have staff scalded skin syndrome recall that this was part of the tricks mnemonic in the beginning of this video in this syndrome these patients also have a positive nikolsky sign it's important that you know it's commonly seen in the pediatric population and is usually preceded by some sort of infection finally we have pamphlets bulgaris and bullus pemphigoid pamphlets vulgaris is characterized by flaccid bully and the mucosa is involved however for bala's pamphlet the ballet are tense and the mucosa is not involved so pemphigus bulgaris and bolas pampagoid are so high-yield because they have overlapping features and they can be easily confused that's why i have this table here to basically compare the main points that examiners love to test how i remember some key features is that pemphigus vulgaris starts with p so pempagus has a positive nikolsky sign and positive mucus involvement while for a ballast pemphigoid it is the opposite but that brings us to the end of our very very high yield dermatology review this video has everything that you need to know for your exam if you have any questions be sure to leave them in the comments below and if you have made it to the end of this video thank you so so much this is like my third attempt at making this because i just wanted to make sure it had all the content that you need for your exam i just think it's so important that we have a resource that is free and a resource that is high yield medical education is so expensive so this is just me doing my part and just trying to help so i really hope that you enjoyed this video in order to let me know that you did be sure to power up the like button hit subscribe and that notification bell thank you thank you thank you so much and to continue learning more be sure to click this video right here thank you so much goodbye