Hypopigmented, finely scaling macules over the upper back and chest of a gym instructor in Chennai become more obvious after sweating, and the scale lifts when the skin is stretched. A KOH mount shows short curved hyphae with clusters of round spores. Which treatment is most appropriate?

Ketoconazole 2% shampoo applied to the trunk

Topical clobetasol propionate cream

Three weeks after two correctly applied courses of permethrin 5% one week apart, a college student still itches at night. Her family was treated at the same time. There are no new burrows, only a few excoriated papules on the trunk and two firm nodules on the axillary folds. What is the best next step?

Reassure; give emollients and an oral antihistamine

Skin biopsy of one of the nodules

Oral ivermectin for the student and her family

A third course of permethrin for the whole family

Thick, yellow, crumbling toenails with subungual debris on both great toes trouble a retired bank clerk with type 2 diabetes, who wants tablets to clear them. He also has chronic plaque psoriasis of the elbows and scalp. What should be done before any oral antifungal is prescribed?

Confirm fungus by KOH mount and culture of nail clippings

Order serum uric acid and an X-ray of the toes

Examine the nails under a Wood lamp

Start oral terbinafine on clinical grounds alone

Dermatophytosis, scabies and antifungal resistance

34 NEET-PG practice questions on Dermatophytosis, scabies and antifungal resistance, part of Dermatology. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Easy
Under a Wood lamp in the skin OPD, a well-defined, finely scaling brown patch in the groin of an obese, diabetic truck driver glows coral red. A KOH mount of the scale shows no hyphae. What is the most likely diagnosis?
1. AErythrasma
2. BCandidal intertrigo
3. CInverse psoriasis
4. DTinea cruris
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Answer: A · Erythrasma
Coral-red fluorescence under Wood light comes from porphyrins made by Corynebacterium minutissimum, the cause of erythrasma. It mimics tinea cruris in the groin, but the KOH mount is negative and the patch lacks an active raised edge. It responds to topical or oral erythromycin or clarithromycin, or topical fusidic acid.
- B: Candidal intertrigo has satellite pustules and shows pseudohyphae on KOH.
- C: Inverse psoriasis gives a glazed red plaque without fluorescence.
- D: Tinea cruris does not fluoresce and the KOH mount shows hyphae.
Remember this
Coral-red Wood lamp fluorescence in a flexure with a negative KOH: erythrasma (Corynebacterium minutissimum).
Question 2 · Medium
Hypopigmented, finely scaling macules over the upper back and chest of a gym instructor in Chennai become more obvious after sweating, and the scale lifts when the skin is stretched. A KOH mount shows short curved hyphae with clusters of round spores. Which treatment is most appropriate?
1. ATopical clobetasol propionate cream
2. BOral terbinafine for 2 weeks
3. COral griseofulvin for 4 weeks
4. DKetoconazole 2% shampoo applied to the trunk
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Answer: D · Ketoconazole 2% shampoo applied to the trunk
Fine scaly hypopigmented macules on the trunk with the evoked scale sign and 'spaghetti and meatballs' on KOH are pityriasis versicolor, caused by Malassezia yeasts. Topical azoles or selenium sulfide, often as a shampoo lathered on the trunk for a few minutes, are first line; oral fluconazole or itraconazole is kept for extensive or recurrent disease. The colour may take months to return even after the fungus is cleared.
- A: Steroids treat inflammation and would worsen a yeast infection.
- B: Oral terbinafine does not reach Malassezia in the stratum corneum.
- C: Griseofulvin has no activity against Malassezia.
Remember this
Pityriasis versicolor: topical azole or selenium first; oral terbinafine and griseofulvin do not work.
Question 3 · Hard
Ejection fraction 30% on the latest echocardiogram: a retired teacher with ischaemic cardiomyopathy, on furosemide, bisoprolol and simvastatin, now has widespread tinea corporis confirmed on a KOH mount after 6 weeks of topical luliconazole failed. He has never taken an oral antifungal, and his liver function tests are normal. Which oral antifungal is most suitable?
1. AFluconazole
2. BOral ketoconazole
3. CItraconazole
4. DTerbinafine
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Answer: D · Terbinafine
Itraconazole has a negative inotropic effect and a warning against use in heart failure, and as a strong CYP3A4 inhibitor it raises simvastatin to levels that cause rhabdomyolysis. Terbinafine is not cardiotoxic and has few CYP3A4 interactions, so it is the safer first oral drug here, with LFT monitoring. Oral ketoconazole is no longer used for skin infection because of hepatotoxicity, and fluconazole is less effective and also interacts.
- A: Fluconazole is less effective in tinea and also raises statin levels.
- B: Oral ketoconazole is withdrawn for skin infection due to liver toxicity.
- C: Itraconazole worsens heart failure and causes simvastatin toxicity.
Remember this
Avoid itraconazole in heart failure and with simvastatin; terbinafine is the safer oral choice.
Question 4 · Medium
Three weeks after two correctly applied courses of permethrin 5% one week apart, a college student still itches at night. Her family was treated at the same time. There are no new burrows, only a few excoriated papules on the trunk and two firm nodules on the axillary folds. What is the best next step?
1. ASkin biopsy of one of the nodules
2. BOral ivermectin for the student and her family
3. CReassure; give emollients and an oral antihistamine
4. DA third course of permethrin for the whole family
Show answerHide answer
Answer: C · Reassure; give emollients and an oral antihistamine
Itch commonly persists for 2-4 weeks after successful scabies treatment because the immune reaction to dead mites and their products continues; nodules can last even longer. Without new burrows or new lesions this is post-scabetic itch, managed with emollients, antihistamines and a mild topical steroid if needed. Repeated scabicides irritate the skin and make the itch worse.
- A: Post-scabetic nodules are typical and do not need a biopsy.
- B: Ivermectin is not needed without signs of active infestation.
- D: More permethrin causes irritant dermatitis and prolongs the itch.
Remember this
Itch for 2-4 weeks after correct treatment is expected; re-treat only for new burrows or lesions.
Question 5 · Medium
Thick, yellow, crumbling toenails with subungual debris on both great toes trouble a retired bank clerk with type 2 diabetes, who wants tablets to clear them. He also has chronic plaque psoriasis of the elbows and scalp. What should be done before any oral antifungal is prescribed?
1. AOrder serum uric acid and an X-ray of the toes
2. BExamine the nails under a Wood lamp
3. CStart oral terbinafine on clinical grounds alone
4. DConfirm fungus by KOH mount and culture of nail clippings
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Answer: D · Confirm fungus by KOH mount and culture of nail clippings
About half of dystrophic nails are not fungal, and nail psoriasis gives the same thickening, discolouration and subungual hyperkeratosis. Oral treatment of onychomycosis lasts months and carries cost, interaction and liver risks, so the diagnosis is confirmed first with a KOH mount and culture (or PAS staining) of clippings taken from the nail bed side. Terbinafine is then the drug of choice for dermatophyte onychomycosis.
- A: Uric acid and X-rays do not separate fungal from psoriatic nail disease.
- B: Dermatophytes in nails do not fluoresce usefully under Wood light.
- C: Empirical terbinafine risks months of needless treatment if this is nail psoriasis.
Remember this
Confirm onychomycosis by KOH and culture before months of oral therapy; psoriasis mimics it.
Question 6 · Easy
Which dermatophyte species, formerly called Trichophyton mentagrophytes genotype VIII, drives the current Indian epidemic of extensive, recalcitrant tinea?
1. AEpidermophyton floccosum
2. BTrichophyton indotineae
3. CMicrosporum canis
4. DTrichophyton rubrum
Answer and explanation in LearnFree account
Question 7 · Easy
Luliconazole cream, widely prescribed in India for tinea corporis, belongs to which antifungal class?
1. AImidazole
2. BTriazole
3. CAllylamine
4. DPolyene
Answer and explanation in LearnFree account
Question 8 · Medium
Concentric, ring-within-ring red scaly lesions cover the waist, buttocks and thighs of a tailor who has applied an over-the-counter cream containing clobetasol, ofloxacin, ornidazole and terbinafine for 5 months. The lesions have little scale and a less clear active edge than usual, and the itch persists. A KOH mount shows many septate hyphae. What is this clinical pattern called?
1. ATinea imbricata
2. BTinea pseudoimbricata
3. CAnnular psoriasis
4. DErythema annulare centrifugum
Answer and explanation in LearnFree account
Question 9 · Medium
A primigravida at 20 weeks of gestation has three itchy, annular scaly plaques on the trunk and waist, each about 4 cm across, for a month. A KOH mount shows septate hyphae. She has not used any cream so far. Which treatment is most appropriate?
1. AOral terbinafine 250 mg daily
2. BOral griseofulvin 500 mg daily
3. CA topical azole cream alone
4. DOral itraconazole 100 mg twice daily
Answer and explanation in LearnFree account
Question 10 · Medium
After 8 months of applying a clobetasol-containing combination cream to tinea cruris, a college athlete has broad, violaceous, linear streaks across the inner thighs and groin, with thin, shiny skin through which veins can be seen. Which mechanism best explains these skin changes?
1. AImmune destruction of melanocytes
2. BMast cell degranulation in the dermis
3. CReduced fibroblast collagen synthesis
4. DFungal invasion of the deep dermis
Answer and explanation in LearnFree account
Question 11 · Medium
A boggy, tender, pus-studded swelling of 5 x 4 cm on the crown of a girl of 6 has grown over 3 weeks; hairs pull out easily and painlessly, and an occipital node is tender. The family has a new kitten. A general surgeon has advised incision and drainage. What is the best management?
1. AIntralesional triamcinolone injection
2. BAn oral antifungal, without incision
3. CTopical mupirocin with warm compresses
4. DIncision and drainage with IV cloxacillin
Answer and explanation in LearnFree account
Question 12 · Medium
As the medical officer of an urban health centre in Kanpur, you see the third member of a joint family this year with itchy annular plaques in the groin and waist. The mother-in-law, her son and his wife have each been treated at different times, and each has relapsed within weeks. They share towels and dry their clothes indoors during the monsoon. Besides oral antifungal treatment, what is the most important step?
1. AGive the index patient a single fluconazole dose
2. BTreat all affected family members together
3. CPrescribe an antihistamine and wait
4. DAdd a stronger steroid-antifungal cream
Answer and explanation in LearnFree account
Question 13 · Medium
Persistent redness, burning, fine telangiectasia and small papules and pustules on the cheeks and chin trouble a young woman who has applied a betamethasone valerate 'fairness' cream to her whole face every day for 2 years. Whenever she stops the cream, the redness and burning flare within days, so she starts it again. Which diagnosis fits best?
1. ASystemic lupus erythematosus
2. BAcne vulgaris
3. CRosacea
4. DTopical steroid-dependent face
Answer and explanation in LearnFree account
Question 14 · Medium
Five weeks into oral terbinafine 250 mg daily for extensive tinea corporis, a bank clerk complains of tiredness, loss of appetite, itching and dark urine. His sclerae are yellow. Serum bilirubin is 4.2 mg/dL and ALT 380 U/L (normal under 40). He drinks no alcohol, and hepatitis A and B serology is negative. What is the next best step?
1. AContinue terbinafine with ursodeoxycholic acid
2. BSwitch to oral itraconazole at once
3. CStop terbinafine and monitor liver function
4. DHalve the terbinafine dose
Answer and explanation in LearnFree account
Question 15 · Medium
During a school health check at a government school in Malappuram, a boy of 7 has two round, scaly patches of hair loss with broken hairs on the occiput and a small tender occipital lymph node. A KOH mount of plucked hairs shows spores packed inside the hair shafts. His mother has applied clotrimazole cream for a month without benefit. What is the right treatment?
1. AA clobetasol-antifungal combination cream
2. BA stronger topical azole such as luliconazole
3. COral terbinafine, with ketoconazole shampoo as an adjunct
4. DShaving the scalp and ketoconazole shampoo alone
Answer and explanation in LearnFree account
Question 16 · Medium
In a man on oral itraconazole for extensive tinea corporis and cruris, the lesions have cleared clinically after 4 weeks: no scaling, no active edge and no itch. He wants to stop the capsules because they are expensive. Indian expert consensus on dermatophytosis would most likely advise what?
1. AStop now as the skin looks normal
2. BContinue for a few more weeks after clinical cure
3. CContinue until a KOH mount is negative at 6 months
4. DSwitch to an antifungal soap alone
Answer and explanation in LearnFree account
Question 17 · Hard
As the medical officer covering an old-age home in Thrissur, you see itchy papules and burrows in 11 of its 40 residents and in two caregivers. One bed-bound resident with dementia has thick crusts on the hands and feet teeming with mites on scraping. Several others have mild itch only, a few have none, and the staff share a single laundry and live with their families in quarters nearby. The home's manager wants to treat just the residents with rashes to save money. Which measure is most important to control the outbreak?
1. ATreat all residents and staff together, with linen washed hot
2. BTreat only residents with rashes, and others if itch appears
3. CIsolate the crusted case and observe the rest for a month
4. DGive antihistamines to all and permethrin to the worst cases
Answer and explanation in LearnFree account
Question 18 · Medium
Glistening, bright red, macerated plaques fill the groin folds and extend onto the scrotum of an obese man with poorly controlled diabetes (HbA1c 10.2%), with small satellite papules and pustules beyond the edge. There is no raised scaly border and no central clearing. Which diagnosis is most likely?
1. AErythrasma
2. BInverse (flexural) psoriasis
3. CCandidal intertrigo
4. DTinea cruris
Answer and explanation in LearnFree account
Question 19 · Medium
Griseofulvin is prescribed for a child with Microsporum tinea capitis. Regarding the drug: 1. It binds fungal microtubules and stops mitosis. 2. Its absorption is better with a fatty meal. 3. It inhibits CYP3A4 and raises warfarin levels. 4. It is effective against pityriasis versicolor. Which statements are correct?
1. A1, 2 and 3 only
2. B2 and 4 only
3. C1 and 2 only
4. D1, 2, 3 and 4
Answer and explanation in LearnFree account
Question 20 · Easy
In a girls' hostel in Kottayam, three roommates have had intense itching for 3 weeks, worse at night, with papules and short wavy burrows in the finger webs, on the wrists and around the umbilicus. Which plan is the first choice?
1. APermethrin 5% cream for all three, repeated after a week
2. BOral ivermectin only for the worst affected girl
3. COral cetirizine and calamine lotion for all three
4. DTopical clobetasol on the itchy areas
Answer and explanation in LearnFree account
Question 21 · Hard
In a paediatric clinic, an 8-month-old infant has a moon face, rapid weight gain, thinned skin and blood pressure above the 95th centile. For 3 months the mother has applied a clobetasol propionate 0.05% combination cream twice daily over the nappy area, trunk and folds for a 'ringworm' rash. An 8 a.m. serum cortisol is low. Apart from treating the rash itself, what is the most appropriate plan for the cream?
1. AContinue it and add oral terbinafine
2. BTaper it gradually and watch for adrenal insufficiency
3. CStop it abruptly and reassure the mother
4. DChange to oral prednisolone 2 mg/kg
Answer and explanation in LearnFree account
Question 22 · Medium
Trichophyton grown from a man with widespread tinea corporis that has failed two courses of oral terbinafine 250 mg daily is sent for molecular testing, and ITS sequencing identifies T. indotineae. Which change in the fungus most likely explains the failure?
1. APoint mutations in the squalene epoxidase (SQLE) gene
2. BOverexpression of lanosterol 14-alpha demethylase (ERG11)
3. CLoss of 1,3-beta-glucan synthase activity
4. DMutation of fungal beta-tubulin genes
Answer and explanation in LearnFree account
Question 23 · Easy
Terbinafine kills dermatophytes by inhibiting which fungal enzyme?
1. AThymidylate synthase
2. BBeta-1,3-glucan synthase
3. CLanosterol 14-alpha demethylase
4. DSqualene epoxidase
Answer and explanation in LearnFree account
Question 24 · Medium
Perifollicular papules and pustules have appeared within an annular scaly plaque on the shin of a woman who shaves her legs and has applied a mometasone-containing cream to the 'ringworm' for 3 months. KOH mount of a plucked hair from a pustule shows fungal hyphae invading the hair. What is the diagnosis and the correct treatment approach?
1. ASteroid acne; topical clindamycin
2. BPseudofolliculitis; stop shaving only
3. CBacterial folliculitis; oral cloxacillin
4. DMajocchi granuloma; needs an oral antifungal
Answer and explanation in LearnFree account
Question 25 · Medium
Nail clippings from suspected onychomycosis are sent for culture. Which medium suits dermatophytes best and suppresses contaminating moulds and bacteria?
1. AChocolate agar with bacitracin
2. BLowenstein-Jensen medium
3. CSDA with cycloheximide and chloramphenicol
4. DSheep blood agar
Answer and explanation in LearnFree account

9 more Dermatophytosis, scabies and antifungal resistance questions

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Dermatophytosis, scabies and antifungal resistance

Under a Wood lamp in the skin OPD, a well-defined, finely scaling brown patch in the groin of an obese, diabetic truck driver glows coral red. A KOH mount of the scale shows no hyphae. What is the most likely diagnosis?

Hypopigmented, finely scaling macules over the upper back and chest of a gym instructor in Chennai become more obvious after sweating, and the scale lifts when the skin is stretched. A KOH mount shows short curved hyphae with clusters of round spores. Which treatment is most appropriate?

Thick, yellow, crumbling toenails with subungual debris on both great toes trouble a retired bank clerk with type 2 diabetes, who wants tablets to clear them. He also has chronic plaque psoriasis of the elbows and scalp. What should be done before any oral antifungal is prescribed?

Which dermatophyte species, formerly called Trichophyton mentagrophytes genotype VIII, drives the current Indian epidemic of extensive, recalcitrant tinea?

Luliconazole cream, widely prescribed in India for tinea corporis, belongs to which antifungal class?

A primigravida at 20 weeks of gestation has three itchy, annular scaly plaques on the trunk and waist, each about 4 cm across, for a month. A KOH mount shows septate hyphae. She has not used any cream so far. Which treatment is most appropriate?

After 8 months of applying a clobetasol-containing combination cream to tinea cruris, a college athlete has broad, violaceous, linear streaks across the inner thighs and groin, with thin, shiny skin through which veins can be seen. Which mechanism best explains these skin changes?

A boggy, tender, pus-studded swelling of 5 x 4 cm on the crown of a girl of 6 has grown over 3 weeks; hairs pull out easily and painlessly, and an occipital node is tender. The family has a new kitten. A general surgeon has advised incision and drainage. What is the best management?

In a man on oral itraconazole for extensive tinea corporis and cruris, the lesions have cleared clinically after 4 weeks: no scaling, no active edge and no itch. He wants to stop the capsules because they are expensive. Indian expert consensus on dermatophytosis would most likely advise what?

In a girls' hostel in Kottayam, three roommates have had intense itching for 3 weeks, worse at night, with papules and short wavy burrows in the finger webs, on the wrists and around the umbilicus. Which plan is the first choice?

Trichophyton grown from a man with widespread tinea corporis that has failed two courses of oral terbinafine 250 mg daily is sent for molecular testing, and ITS sequencing identifies T. indotineae. Which change in the fungus most likely explains the failure?

Terbinafine kills dermatophytes by inhibiting which fungal enzyme?

Nail clippings from suspected onychomycosis are sent for culture. Which medium suits dermatophytes best and suppresses contaminating moulds and bacteria?