Dermatology for NEET PG: six skin pictures and the one thing to look at first

Answer: B. Nail 2

Nail 2, koilonychia. In profile the plate is turned up at its edges with a hollow in the middle, deep enough to hold a drop of water, which is the bedside demonstration of the sign. Iron is needed for the keratin of the plate, so deficiency makes it thin and soft. The change takes months to appear and months to reverse after treatment.

Why the closest rival loses: nail 1 (A) has pitting and a lifted free edge, which is psoriasis of the nail. Nail 3 (D) is clubbing, which points to suppurative lung disease, cyanotic heart disease or malignancy. Nail 4 (C) shows splinter haemorrhages, which raise infective endocarditis, though trauma is far commoner. Spoon for iron, drumstick for the lung.

Recallab question 55040 · Skin › Appendages, Tumours & Miscellaneous · reference: Fitzpatrick's Dermatology

Answer: C. Pemphigus vulgaris

Pemphigus vulgaris. The level of the split decides how the blister behaves. In section 2 the split lies within the epidermis, just above the basal layer, which stays attached to the basement membrane. The cells above have lost their attachments to each other and float free. A roof of live epidermal cells has no strength, so the blister is flaccid and collapses early: patients present with erosions rather than intact blisters.

Why the closest rival loses: bullous pemphigoid (D) is section 3, split below the basement membrane, which is why those blisters stay tense. Bullous impetigo (A) is section 1, split just under the horny layer, the most superficial of the three. Dermatitis herpetiformis (B) also splits below the membrane. Deep split, tense blister; shallow split, raw erosion.

Recallab question 55038 · Skin › Vesiculobullous & Connective Tissue · reference: Fitzpatrick's Dermatology

Answer: A. A halo naevus

A halo naevus. Lesion 1 is small, even in colour and regular, sitting centrally in a symmetrical ring of white skin. Cytotoxic T cells attack the naevus cells and the melanocytes around them, which leaves a clean halo; later the mole itself may vanish. In a teenager it is benign, though the rest of the skin is examined, and it is commoner in people with vitiligo.

Why the closest rival loses: a patch of vitiligo (B) is lesion 3, a white patch with nothing in its centre. A Meyerson naevus (C) carries a red, scaly eczematous halo, not a smooth white ring. A regressing melanoma (D) is patchy and irregular; lesion 2, varied in colour with a notched border, is the worrying one.

Recallab question 55238 · Skin › Disorder Of Pigmentation · reference: Fitzpatrick's Dermatology

Answer: B. Asteatotic eczema

Asteatotic eczema. Older skin makes less surface lipid and loses water easily, and winter air, hot water and soap strip what barrier is left. The dry, scaly skin develops a network of fine red fissures that divides the surface into polygons, like crazy paving, and the shins are the commonest site. Soap substitutes and heavy emollients restore the barrier.

Why the closest rival loses: discoid eczema (A) forms separate, coin-shaped, often weeping plaques, not a continuous cracked network. Venous eczema (D) comes with ankle swelling, brown staining and varicose veins, none of which is in the story. Ichthyosis vulgaris (C) is lifelong, with fine scale, and does not appear for the first time in old age.

Recallab question 57942 · Skin › Eczema · reference: Fitzpatrick's Dermatology

Answer: A. Mount 1, dermatophyte hyphae

Mount 1, dermatophyte hyphae. An annular plaque with a raised, active edge and central clearing is classic tinea corporis. Dermatophytes show as long, branching, septate hyphae that break into chains of arthrospores, as in mount 1. Misusing a topical steroid on an unrecognised dermatophyte infection produces tinea incognito, where the active edge is lost and the diagnosis gets harder.

Why the closest rival loses: mount 3 shows short, curved hyphae with clusters of round spores, the appearance of Malassezia, not the long branching septate hyphae of a dermatophyte. So option C names the wrong mount for a dermatophyte, and option B names the right organism for mount 3 but the wrong disease: Malassezia causes patchy pigment change, not a spreading annular edge. Mount 2 (D) shows budding yeast and pseudohyphae, which fits Candida in moist folds with satellite pustules, not a plaque on the thigh.

Recallab question 55358 · Skin › Fungal Infection · reference: Fitzpatrick's Dermatology

Answer: A. A burns or intensive care unit

A burns or intensive care unit. The outlines are staged by the share of skin that has detached: under 10 per cent, 10 to 30 per cent, over 30 per cent. At 20 per cent she sits in the overlap band between Stevens-Johnson syndrome and toxic epidermal necrolysis. Detached epidermis loses fluid, protein and heat and lets infection in, as a burn does, so she needs warming, barrier nursing, fluid balance and wound care of burns-unit standard, and the risk grows with the area lost.

Why the closest rival loses: a general medical ward (C) cannot give the fluid, temperature and wound care that a burn of this size needs. Discharge (B) is out of the question: a fifth of the skin detached is life-threatening. An isolation ward (D) answers an infection: staphylococcal scalded skin syndrome follows one and splits the skin high in the epidermis. This is a drug reaction. Under 10 per cent is Stevens-Johnson, over 30 is toxic epidermal necrolysis, and the culprit drug is stopped at once.

Recallab question 56242 · Skin › Drugs & Drug reactions · reference: Fitzpatrick's Dermatology