Master every high-yield dermatology topic for NEET PG 2026: papulosquamous disorders, vesiculobullous diseases, leprosy, pigmentary disorders, connective tissue diseases, STIs, drug reactions, and hair/nail disorders with real exam patterns.
Version 1.0 — Published April 2026
Dermatology contributes 10-14 questions to NEET PG, with leprosy and psoriasis generating the most reliable marks. Master these 8 high-yield areas:
Dermatology is the visual specialty — a field where the diagnosis often rests on recognizing a morphological pattern, knowing a pathognomonic sign, or distinguishing two conditions that look superficially similar. NEET PG tests dermatology through image-based questions, clinical vignettes with described lesion morphology, and classification-based questions (especially leprosy). The rewarding part: the question pool is predictable, and the same signs, diseases, and differentials repeat with high fidelity.
This guide covers the eight areas that generate the highest question density. Each section gives you the diagnostic criteria, pathognomonic features, and clinical associations that NBE tests. Pair it with the psoriasis vs eczema image walkthrough for visual pattern training and the medicine high-yield guide for systemic disease manifestations in skin.
Papulosquamous disorders are characterized by scaly papules and plaques. Psoriasis is the most tested condition in this group, followed by lichen planus.
Psoriasis is a chronic, relapsing, immune-mediated inflammatory disease characterized by well-defined, erythematous plaques with silvery-white micaceous scales, most commonly on extensor surfaces (elbows, knees), scalp, and lumbosacral area.
This content is for educational purposes for NEET PG exam preparation. It is not a substitute for professional medical advice, diagnosis, or treatment. Clinical information has been reviewed by qualified medical professionals.
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Join on Telegram →Pathognomonic signs:
Histopathology: Acanthosis, parakeratosis (nuclei retained in stratum corneum), Munro microabscesses (neutrophils in the stratum corneum), spongiform pustules of Kogoj (neutrophils in the stratum spinosum), suprapapillary thinning with dilated tortuous capillaries.
Nail changes in psoriasis (tested as image or description):
Psoriatic arthritis affects 10-30% of psoriasis patients. Five patterns: asymmetric oligoarthritis (most common), symmetric polyarthritis (mimics RA), DIP predominant (pathognomonic), spondylitis, and arthritis mutilans (opera glass hand). DIP involvement distinguishes psoriatic arthritis from RA (RA spares DIP).
Lichen planus is a chronic inflammatory condition affecting skin, mucous membranes, hair, and nails. The classic description uses the 6 Ps: Purple, Polygonal, Planar (flat-topped), Pruritic Papules and Plaques.
Wickham striae — fine white reticular lines on the surface of lichen planus papules, best seen with a dermatoscope or after applying oil. This is the pathognomonic sign.
Histopathology: Interface dermatitis with a band-like (lichenoid) lymphocytic infiltrate hugging the basal layer, saw-tooth acanthosis, civatte bodies (colloid/apoptotic bodies at the dermoepidermal junction), and Max-Joseph spaces (clefts at the DEJ from basal cell destruction). This histological pattern is the most tested aspect of lichen planus in NEET PG.
Oral lichen planus — white reticular lesions on buccal mucosa. Considered a premalignant condition (1-2% risk of squamous cell carcinoma). Erosive oral lichen planus is the variant with highest malignant potential (IADVL Textbook of Dermatology, 4th Edition).
Pityriasis rosea is a self-limiting papulosquamous disorder, likely viral in etiology (HHV-6, HHV-7 association).
Herald patch — a single, oval, salmon-pink plaque with a "collarette" scale (fine scale at the periphery with central clearing) that appears 1-2 weeks before the generalized eruption. The herald patch is the diagnostic clue in NEET PG vignettes.
Christmas tree pattern — the generalized eruption follows skin cleavage lines (Langer lines) on the trunk, creating a "Christmas tree" distribution on the back. Lesions are smaller versions of the herald patch.
Key differential: Secondary syphilis can mimic pityriasis rosea. Always order VDRL/RPR in sexually active patients with a pityriasis rosea-like rash, especially if palms and soles are involved (pityriasis rosea typically spares palms and soles; syphilis involves them).
Vesiculobullous diseases generate 2-3 questions per NEET PG paper. The key is distinguishing the level of blister formation and the immunofluorescence pattern.
| Feature | Pemphigus vulgaris | Bullous pemphigoid |
|---|---|---|
| Age | 40-60 years | >60 years |
| Blister type | Flaccid (ruptures easily) | Tense (intact longer) |
| Level | Intraepidermal (suprabasal) | Subepidermal |
| Nikolsky sign | Positive | Negative |
| Oral involvement | Common (often first presentation) | Uncommon |
| Histology | Acantholysis (suprabasal cleft), row of tombstones (basal cells remain attached to basement membrane) | Subepidermal bulla with eosinophils |
| DIF | Intercellular IgG — fishnet/lace pattern | Linear IgG and C3 at basement membrane zone |
| Antibody target | Desmoglein 3 (mucosal) and desmoglein 1 (mucocutaneous) | BP180 (type XVII collagen) and BP230 |
| Mortality (untreated) | High (previously near 100%) | Lower |
Tzanck smear shows acantholytic cells (rounded keratinocytes with large nuclei and perinuclear halo) in pemphigus. It is a bedside diagnostic test — scrape the base of a fresh blister, smear on a slide, stain with Giemsa. Positive Tzanck smear + positive Nikolsky sign = strong pemphigus support.
Dermatitis herpetiformis is a vesiculobullous disease with grouped (herpetiform) vesicles on extensor surfaces (elbows, knees, buttocks, upper back).
Association: Nearly 100% of DH patients have celiac disease (gluten-sensitive enteropathy) on jejunal biopsy, even if asymptomatic. This is the most tested association in NEET PG.
DIF: Granular IgA deposits at the dermal papillae tips — this is pathognomonic and distinguishes DH from linear IgA bullous dermatosis (which shows linear IgA at the BMZ).
Treatment: Dapsone provides rapid symptomatic relief (within 24-48 hours). Gluten-free diet is the definitive long-term treatment and allows eventual dapsone discontinuation (Rook's Textbook of Dermatology, 9th Edition).
Leprosy (Hansen disease), caused by Mycobacterium leprae, is the most tested dermatology topic in NEET PG. It covers classification, clinical features, treatment, and reactions — generating 2-3 questions per paper.
The spectrum from tuberculoid to lepromatous reflects the host immune response:
| Feature | TT | BT | BB | BL | LL |
|---|---|---|---|---|---|
| Skin lesions | 1-3, well-defined | Few, well-defined | Several, intermediate | Many, poorly defined | Innumerable, diffuse |
| Surface | Dry, scaly | Dry | Slightly shiny | Shiny | Shiny, infiltrated |
| Nerve involvement | Early, severe, asymmetric | Early, asymmetric | Variable | Late, symmetric | Late, symmetric |
| Bacterial index | 0 | 0-1+ | 2-3+ | 3-4+ | 5-6+ |
| Lepromin test | Strongly positive | Weakly positive | Negative | Negative | Negative |
| CMI to M. leprae | Strong (Th1) | Moderate | Unstable | Weak | Absent (Th2) |
WHO operational classification simplifies this for treatment purposes: Paucibacillary (PB) = 1-5 skin lesions, 0-1 nerve involved (covers TT, BT). Multibacillary (MB) = >5 skin lesions or >1 nerve involved (covers BB, BL, LL) or skin smear positive.
| Regimen | PB (6 months) | MB (12 months) |
|---|---|---|
| Monthly supervised | Rifampicin 600 mg | Rifampicin 600 mg + Clofazimine 300 mg |
| Daily self-administered | Dapsone 100 mg | Dapsone 100 mg + Clofazimine 50 mg |
Single-lesion PB: ROM regimen (single dose of Rifampicin 600 mg + Ofloxacin 400 mg + Minocycline 100 mg) — though WHO now recommends standard PB-MDT.
| Feature | Type 1 (Reversal reaction) | Type 2 (ENL — Erythema nodosum leprosum) |
|---|---|---|
| Mechanism | Delayed type hypersensitivity (CMI upgrade) | Immune complex deposition (Type III) |
| Occurs in | BT, BB, BL (borderline types) | BL and LL only |
| Clinical | Existing lesions become erythematous, edematous; nerve tenderness and swelling; new motor/sensory deficit | New tender erythematous nodules on normal skin; fever; arthralgia; iridocyclitis; orchitis |
| Treatment | Prednisolone (for nerve involvement) | Thalidomide (drug of choice), or prednisolone |
Type 1 reaction is the most common cause of nerve damage in leprosy. The nerves at highest risk are the ulnar nerve (most commonly affected in leprosy overall), lateral popliteal (common peroneal), posterior tibial, and facial nerve.
Thalidomide is the drug of choice for severe ENL but is absolutely contraindicated in women of childbearing age due to teratogenicity (phocomelia). Prednisolone is used when thalidomide is contraindicated (WHO leprosy treatment guidelines).
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Start Free Practice →Pigmentary disorders test the ability to differentiate depigmented from hypopigmented lesions and to identify the pathogenic mechanism.
Vitiligo is an autoimmune disorder causing progressive depigmentation through destruction of melanocytes. It affects 0.5-2% of the population globally, with onset most commonly in the second or third decade.
Clinical features: Well-defined, chalk-white (not cream or off-white) macules and patches, often symmetric. Common sites: periorbital, perioral, acral (fingers, toes), genital, axillary. Wood lamp examination shows bright white fluorescence with sharp borders (enhanced contrast) — this helps detect early or subtle lesions in fair-skinned individuals.
Types:
Treatment: Topical corticosteroids or tacrolimus (face, intertriginous areas), narrowband UVB phototherapy (mainstay for generalized vitiligo), and surgical methods (suction blister melanocyte transplantation) for stable, localized disease unresponsive to medical therapy.
Melasma is an acquired symmetric hypermelanosis affecting sun-exposed areas of the face, most common in women of reproductive age. Hormonal influences (pregnancy, oral contraceptives) and UV exposure are the primary triggers.
Types by Wood lamp:
Treatment: Strict sun protection (SPF 30+, physical sunscreens), triple combination cream (hydroquinone 4% + tretinoin 0.05% + fluocinolone 0.01% — "Kligman formula"), chemical peels (glycolic acid), and laser for refractory cases.
Albinism results from defective melanin synthesis. The most commonly tested form is OCA type 1 (tyrosinase-negative) — complete absence of melanin in skin, hair, and eyes. Autosomal recessive inheritance. Clinical features: white hair, pink skin, translucent irides, nystagmus, photophobia. Increased risk of skin cancers (SCC, BCC) due to absent UV protection.
Connective tissue diseases with dermatological manifestations are tested in both dermatology and medicine sections of NEET PG.
SLE affects women of childbearing age (F:M ratio 9:1). The skin findings most tested:
Key autoantibodies: ANA (sensitive but not specific, 95%+), anti-dsDNA (specific for SLE, correlates with renal disease activity), anti-Smith (most specific for SLE, low sensitivity).
Dermatomyositis is an inflammatory myopathy with characteristic skin findings. The skin changes may precede muscle weakness (amyopathic dermatomyositis).
Malignancy association: Adult dermatomyositis has a 15-30% association with internal malignancy (ovarian, lung, GI, breast). Cancer screening is mandatory at diagnosis and for 3 years after (Fitzpatrick's Dermatology, 9th Edition).
Scleroderma (systemic sclerosis) is characterized by skin fibrosis and internal organ involvement.
Limited (CREST): Calcinosis, Raynaud phenomenon, Esophageal dysmotility, Sclerodactyly, Telangiectasia. Anti-centromere antibody positive. Better prognosis. Pulmonary hypertension is the main cause of death.
Diffuse: Rapid skin thickening beyond elbows/knees, early internal organ involvement. Anti-Scl-70 (anti-topoisomerase I) antibody positive. Renal crisis (malignant hypertension) is the most feared complication — treated with ACE inhibitors.
STIs are tested through clinical vignette descriptions of genital ulcers, with emphasis on differentiating features.
Primary syphilis (3 weeks post-exposure): Painless chancre — a clean-based ulcer with indurated, rolled edges at the site of inoculation. Non-tender inguinal lymphadenopathy. The chancre heals spontaneously in 3-6 weeks. Darkfield microscopy shows spirochetes.
Secondary syphilis (6-8 weeks post-primary): Widespread symmetric maculopapular rash involving palms and soles (key feature — very few conditions cause palmar/plantar rash: syphilis, Rocky Mountain spotted fever, hand-foot-mouth disease, Kawasaki). Condylomata lata (moist, flat, highly infectious warts in intertriginous areas — distinguish from condylomata acuminata of HPV which are dry and pointed). Mucous patches. Moth-eaten alopecia. Generalized lymphadenopathy.
Tertiary syphilis (years later): Gumma (granulomatous lesions in skin, bone, liver), cardiovascular syphilis (aortitis of ascending aorta — tree bark appearance, aortic regurgitation, aortic aneurysm), neurosyphilis (tabes dorsalis — lightning pains, Argyll Robertson pupil — accommodates but does not react to light, Charcot joints).
Congenital syphilis — Hutchinson triad: Interstitial keratitis, Hutchinson teeth (peg-shaped, notched upper central incisors), and sensorineural deafness (VIII nerve).
Chancroid produces a painful genital ulcer (unlike the painless chancre of syphilis). The ulcer has ragged, undermined edges and a necrotic base. Tender inguinal lymphadenopathy that may suppurate and form buboes (draining sinuses). Diagnosis: Gram stain shows "school of fish" pattern (parallel chains of gram-negative coccobacilli).
LGV is caused by Chlamydia trachomatis serovars L1, L2, L3. Three stages: painless papule/ulcer (often missed), then inguinal lymphadenopathy (the bubo stage — unilateral, fluctuant, may suppurate). The groove sign (sign of Greenblatt) — a groove between the inguinal and femoral lymph node groups created by the inguinal ligament — is pathognomonic. Late stage: proctitis, strictures, elephantiasis of genitalia.
Treatment: Doxycycline 100 mg BD for 21 days.
Drug reactions are tested through clinical scenarios with the causative drug as the answer or through clinical description identification.
SJS and TEN are on the same spectrum, differentiated by the body surface area (BSA) of epidermal detachment:
| Category | BSA detachment | Mortality |
|---|---|---|
| SJS | <10% | 1-5% |
| SJS-TEN overlap | 10-30% | 10-30% |
| TEN | >30% | 25-50% |
Common causative drugs (high-yield for MCQs): Carbamazepine, allopurinol, sulfonamides (cotrimoxazole), phenytoin, nevirapine, NSAIDs (piroxicam, especially), and lamotrigine.
Clinical features: Prodromal fever and malaise, then painful skin involvement with target lesions, hemorrhagic erosions of mucous membranes (oral, ocular, genital), and progressive epidermal detachment. Nikolsky sign is positive (epidermis slides off with lateral pressure). Mucosal involvement is mandatory for diagnosis.
Management: Immediate withdrawal of the offending drug (the single most important step). Supportive care in a burns unit/ICU. IVIG and cyclosporine are used in severe cases. Corticosteroids are controversial. SCORTEN prognostic scoring system predicts mortality based on 7 parameters (age, malignancy, BSA, heart rate, BUN, glucose, bicarbonate).
FDE is characterized by a round, well-defined, violaceous (dusky red-brown) plaque that recurs at the same site with each drug exposure. Post-inflammatory hyperpigmentation persists between episodes. Common culprits: cotrimoxazole (most common), tetracyclines, NSAIDs, metronidazole. The "same site recurrence" is the diagnostic clue in NEET PG.
DRESS (Drug Reaction with Eosinophilia and Systemic Symptoms) presents 2-8 weeks after starting the causative drug with fever, morbilliform rash, facial edema, lymphadenopathy, and internal organ involvement (hepatitis most common, also nephritis, pneumonitis). Peripheral eosinophilia (>1500/microL) or atypical lymphocytes are characteristic. Common drugs: anticonvulsants (carbamazepine, phenytoin, lamotrigine), allopurinol, dapsone, minocycline. HHV-6 reactivation plays a role in pathogenesis.
Hair and nail disorders appear as 1-2 questions per NEET PG, often as image-based or one-liner questions.
Alopecia areata is an autoimmune condition causing well-defined, oval or round patches of non-scarring hair loss. The scalp skin appears normal (no scarring, no scaling — distinguishing it from tinea capitis and discoid lupus).
Pathognomonic sign: "Exclamation mark hairs" — short, broken hairs (2-3 mm) that are narrower at the base than at the tip, found at the margins of the patch. These represent dystrophic anagen hairs and are diagnostic.
Variants: Alopecia totalis (complete scalp hair loss), alopecia universalis (complete body hair loss). Nail changes in alopecia areata: fine pitting (regular, geometric "grid-like" pattern — in contrast to the irregular pitting of psoriasis).
Treatment: Intralesional triamcinolone (first-line for localized patches), topical minoxidil, contact immunotherapy (DPCP/SADBE) for extensive disease, and JAK inhibitors (baricitinib — FDA approved for severe alopecia areata).
Onychomycosis is fungal infection of the nail, most commonly caused by dermatophytes (Trichophyton rubrum is the most common organism). It accounts for 50% of all nail disorders.
Types: Distal and lateral subungual (most common), proximal subungual (associated with immunosuppression — HIV marker), superficial white, and total dystrophic.
Diagnosis: KOH mount of nail clippings shows septate hyphae. Fungal culture on Sabouraud dextrose agar confirms the species.
Treatment: Terbinafine oral (drug of choice for dermatophyte onychomycosis — 12 weeks for toenails, 6 weeks for fingernails). Itraconazole pulse therapy (200 mg BD for 1 week/month, 2-3 pulses for fingernails, 3-4 for toenails) is an alternative. Topical ciclopirox or amorolfine nail lacquer for mild, distal disease.
Dermatology contributes 10-14 questions in NEET PG (2021-2024 analysis). Leprosy accounts for 2-3 questions almost every year. Psoriasis, pemphigus, drug reactions, and STIs are the next most tested. Image-based dermatology questions appear 3-4 times per paper.
Leprosy is the single most tested topic because it covers classification, microbiology, immunology, clinical features, treatment, and reactions. It appears in 2-3 questions per paper. Psoriasis is second, followed by vesiculobullous diseases.
Pemphigus: flaccid blisters, intraepidermal, Nikolsky positive, acantholysis, fishnet DIF. Pemphigoid: tense blisters, subepidermal, Nikolsky negative, no acantholysis, linear DIF. Remember: pemphiGUS = GUShy (flaccid), pemphiGOID = GOod (tense).
The spectrum from TT (tuberculoid) to LL (lepromatous) reflects host immunity. TT: few well-defined lesions, high CMI, low bacilli. LL: innumerable diffuse lesions, absent CMI, high bacilli. BB is the most unstable form.
SJS/TEN (differentiated by BSA: SJS less than 10%, TEN greater than 30%), DRESS (eosinophilia, systemic involvement), and FDE (same site recurrence). Key drugs: carbamazepine, allopurinol, sulfonamides, phenytoin.
Vitiligo: chalk-white, well-defined, normal texture, bright white on Wood lamp. Pityriasis versicolor: hypopigmented with scaling, KOH positive. Leprosy: hypopigmented with hypoesthesia. Nevus depigmentosus: stable from birth, not chalk-white.
Primary: painless chancre. Secondary: maculopapular rash on palms and soles, condylomata lata. Tertiary: gumma, aortitis, neurosyphilis (tabes dorsalis, Argyll Robertson pupil). Congenital: Hutchinson triad.
Koebner phenomenon is the development of disease-specific lesions at sites of trauma. Classic diseases: psoriasis, lichen planus, vitiligo, and warts. The linear/geometric distribution pattern following injury lines is the clinical clue.
Start your dermatology preparation today. Open the Dermatology subject page and solve your first 15 MCQs — the morphological patterns you learn now will unlock marks across dermatology and medicine on exam day. For AI-powered image-based MCQs with visual explanations, explore NEETPGAI Pro.
Written by: NEETPGAI Editorial Team Reviewed by: Pending SME Review Last reviewed: April 2026
This article is reviewed by qualified medical professionals for clinical accuracy and exam relevance. For corrections or updates, contact the editorial team.