📚 Question Bank

A linear distribution of nodules is seen in sporotrichosis.

Sporotrichosis is an acute or chronic fungal infection caused by Sporothrix schenckii and closely related species.

The given images show the distribution of lesions along lymphatics.

Option A: Lichen planus- Purple polygonal, flat-topped papules are seen. Option C: Chromoblastomycosis- multiple hypertrophic plaques are seen. Option D: Tinea circinata- circular, scaly lesions with central clearing are seen.

The vector for Chiclero ulcer or new world leishmaniasis is the lutzomyia sandfly.

The vector bites humans, typically those working as chicle collectors, causing lesions on the side of the face or behind the ears. Lesions on the pinna of the ear may invade cartilage, take many years to heal, and destroy the pinna.

The images below show the Chiclero ulcer and lutzomyia sandfly.

Option A: Phlebotomus sandfly is the vector for old-world leishmaniasis. Option C: Reduviid bug is the vector for Chagas disease.

Option D: Trombiculid mite is the vector for scrub typhus.

The above scenario is suggestive of cutaneous leishmaniasis.

The classical lesion in cutaneous leishmaniasis is characterized by erythematous nodule/plaque which then ulcerates and becomes crusted. Diascopy usually reveals 'apple jelly nodules'.

Note: 'Apple jelly nodules' on diascopy are seen in both cutaneous leishmaniasis and lupus vulgaris. The skin lesion in cutaneous leishmaniasis shows central crusting, whereas in lupus vulgaris it shows central scarring.

The image shows apple jelly nodule seen on diascopy.

The case scenario suggests a diagnosis of post-kala-azar dermal leishmaniasis. The drug of choice for this condition is miltefosine.

Approach to the case:

The patient hails from a kala-azar endemic zone—Bihar. The rash appears 1-2 years after a history of prolonged fever, which suggests visceral leishmaniasis. There are 2 other differentials—leprosy and tinea versicolor.

• The presence of hypopigmented macules over the trunk and face, suggests a differential of leprosy, but the nerves and sensations are normal, hence ruling it out.
• There is no scaling visible in the lesions, ruling out tinea versicolor.

In kala-azar, after a variable period of years or months, diffuse nodulation begins to develop in these macules. The rash is progressive over many years and seldom heals spontaneously. As it may persist for up to 20 years, these patients may act as a chronic reservoir of infection.

The image below shows post-kala-azar cutaneous leishmaniasis.

The image shows a magnified view of a burrowing trail of the scabies mite. The scaly patch on the left was caused by the scratching and it marks the mite's entry point into the skin. The mite has burrowed to the top-right, where it can be seen as a dark spot at the end. Burrow is the characteristic lesion of scabies.

Scabies is an ectoparasitic infestation caused by the Sarcoptes scabiei var. hominis.

The characteristic symptoms include intense itching and superficial burrows. In most people, the trails of the burrowing mites appear brownish linear or s-shaped tracks in the skin and occur as a result of excavation of the adult mite in the epidermis. These are found in the webspaces, feet, ventral wrists, elbows, back, breasts, buttocks, and external genitals.

Larva currens and cutaneous larva migrans presents as pruritic erythematous papule at the site of penetration of the hookworms with an erythematous serpiginous larva track.

Pediculosis lesions present as erythematous papules with maculae cerulae.

Scabietic burrows are mainly seen in the stratum corneum.

The incubation period of scabies is 3–4 weeks (21-28 days).

However, reinfection of a previously cured individual may provoke immediate symptoms.

The image shows a characteristic scabietic burrow seen on an adult and the given clinical scenario is suggestive of scabies in the neonate as well. Scabies in neonates can occur on the face, an area unlikely in adults.

Locations of infection:

Neon ates

Face

Scalp Palms Soles

Adults

Finger and feet, webspace s

Ventral wrist, elbow Back, buttock External genitalia

Burrows are absent in animal scabies. Skin lesions resulting from contact with animal scabies are usually composed of small pruritic weals or papules, which are frequently excoriated, and resemble human scabies, but without burrows.

Water-washed diseases are infections that are caused by poor personal hygiene resulting from inadequate water availability for e.g. scabies.

The characteristic symptoms of a scabies infection include intense itching which usually manifests 3-4 weeks after infestation and superficial burrows (pathognomonic).

Circle of Hebra is an imaginary circle formed by connecting the main sites of involvement in scabies.

Multiple itchy, eczematous, exudative, papulovesicular lesions on the face, palms, soles, and trunk are characteristic of infantile scabies.

Scabies is transmitted by close contact from human to human or from pet animals to humans. Thus, there are usually several cases in the same household.

Option A: Pediculosis presents with severe itching, visible lice on the scalp, and lice eggs (nits) on the hair shafts.

Option C: Infantile eczema shows an erythematous itchy rash over extensors, elbows, and knees

Option D: Impetigo contagiosa or non-bullous impetigo presents with erythematous vesicles and honey-colored crusts.

Face is spared in adults with scabies.

In adults, the mites affect the regions in the circle of Hebra - web spaces, ventral wrists, the ulnar border of the forearm, elbow flexures, axillae, areola, breasts of female, umbilicus, genitals, and inner aspect of the thigh. Face, palms, and soles are affected in infantile scabies.

Option A: The number of lesions does not correspond to the number of mites. Option B: Topical 5 permethrin is used in the treatment of scabies, not oral.

Option D: Itching that worsens at night and when the patient is warm. Nocturnal pruritis is the most common symptom associated with scabies.

A single overnight application of 5 permethrin cream from neck to toe in adults and from head to toe in children is the drug of choice for the treatment of scabies in all ages including infants (at least 2 months old) and pregnant women.

The circumflex accentlike image (as the French letter ‘ô’) seen in the image represents the head and the two pairs of front legs of the scabies mite. Ivermectin is the only oral medication that can be used in the treatment of scabies.

Oral ivermectin interrupts the γaminobutyric acid-induced neurotransmission of many parasites including mites. It is given as a single dose of 200mcg/kg in patients gt;2 years and gt;15 kg. A second dose is necessary 7–14 days later due to the lack of ovicidal action of the drug.

Topical formulations:

• 5 permethrin
• Gamma benzene hexachloride
• Lindane
• Crotamiton

All family members, even if asymptomatic need to be treated simultaneously for this condition to prevent reinfection and the clothing needs to be disinfected simultaneously.

The given clinical scenario and the image of the Sarcoptes scabiei mite are suggestive of scabies. Oral ivermectin acts by blocking chemical transmission across invertebrate nerve synapses that utilize glutamate or γ-aminobutyric acid (GABA), resulting in paralysis and death of the mite

It is not indicated in infants and pregnant women.

Option A: A single overnight application of 5 permethrin cream from neck to toe in adults and from head to toe in children is the drug of choice for the treatment of scabies in all ages including infants (gt;2 months old) and pregnant women.

Option B: Topical sulfur applications can be safely used in infants lt;2 months of age, as well as in breastfeeding and pregnant mothers.

Option D: Topical 1 lindane cream is contraindicated in children, pregnant ladies, and seizure disorder as it is known to cause neurotoxicity.

The image on the left shows generalized papulonodular rash and that on the right shows a characteristic burrow resembling a ‘jetwithcontrail’ on dermoscopy which is suggestive of scabies. Tzanck smear is used in diagnosing herpes simplex infections and not scabies.

The following techniques can be used to diagnose scabies:

• Skin scraping and microscopy - The material is scraped off with a blunt scalpel and is placed in mineral oil on a microscope slide. The presence of mites, eggs, fragments of eggshells, or scybala (hardened masses of feces) confirms the diagnosis.
• Dermoscopy - Useful for detecting burrows and visualizing their contents.
• 10x magnification - mini triangle sign, maturing eggs that show minute heads of maturing mite within the egg
• 40x magnification - The mite in its burrow resembling a ‘jetwithcontrail’
• Adhesive-tape test - After firmly applying the adhesive side of the tape onto an appropriate skin lesion of patients, the tape is pulled off and transferred directly onto a slide for microscopy to visualize the mites.
• Skin biopsy

Nodular scabies is an atypical presentation of scabies. It is highly pruritic.

It presents as a few violaceous, pruritic nodules are often localized on the groin, axillae and male genitalia. They represent a hypersensitivity reaction to mite antigens. These nodules persist for weeks or months after anti scabies treatment.

The image below shows nodular scabies.

This is the clinical presentation of Norwegian scabies or human-crusted scabies. The reason for this association with mental abnormality(Down's syndrome) could be a lack of appreciation of pruritus.

Crusted scabies (Norwegian or hyperkeratotic scabies) is seen in:

• Immunocompromised
• Debilitated patients
• Neurologic disorders
• Downs syndrome
• Organ transplant recipients
• Hansen’s disease
• AIDS

Crusted scabies occurs in people with an inadequate immune response to the mite, allowing them to multiply. It is the most common type of scabies causing institutional breakouts. It is called 'Norwegian' because it was first described in lepers of Norway.

Crusts and scales teem with mites, and the face and scalp are especially involved. Hyperkeratotic fissured plaques over palms, soles, and buttocks. Nails show subungual hyperkeratosis.

Treatment includes oral ivermectin, topical permethrin, and keratolytic agents for the crusting. The images given below show Norwegian scabies.

Option A: If topical steroids are used on scabies lesions, the clinical picture modifies to mimic other dermatoses and is called scabies incognito.

Option B: Animal scabies lesions are similar to human scabies with itchy papules except for the burrows.

Option D: Nodular scabies presents as violaceous nodules are present over the genitalia.

The image shows scraping lesions on the upper back and numerous lice in the seams of her clothing which are suggestive of pediculosis corporis ('pediculosis vestimenti' or 'vagabond's disease') caused by body lice (specifically pediculus corporis).

It is a disease of poor, homeless, and wandering people (vagabonds), hence, the name Vagabond’s disease. Itching is due to the reaction to salivary antigens of the louse bites.

Body lice are vectors of important diseases like relapsing fever (Borrelia recurrentis), trench fever (Bartonella quintana), and epidemic typhus (Rickettsia prowazekii)

Bed linens and clothes should be systematically decontaminated. Although this is usually enough in most cases, thorough washing of the body with soap followed by application of pyrethrins/pyrethroids or malathion for 8–24 h can also be recommended.

Maculae cerulae are blue-red/grey-colored macules on the skin characteristically seen in pediculosis pubis which is caused due to the infestation by pubic louse (Pthirus pubis/crab louse). They mark the hemosiderin-stained purpuric spots where lice have fed.

The image given below shows pediculosis pubis- countless white spots and lice in pubic hairs.

The image shows crab louse or Pthirus pubis that causes pediculosis pubis. It has a distinctive squat body, and the second and third pairs of legs carry heavy, pincerlike claws.

This louse commonly infests pubic hair (most common), as well as hairs of the abdomen, chest, legs, arms, and eyelashes. Scalp hair is uninvolved due to its high density. This is often transmitted sexually and by close contact.

Blue colored macules on the trunk and inner aspects of thighs are seen called maculae ceruleae. Treatment is with 1 permethrin and oral ivermectin.

(Infestation of the eyelashes with nits is treated with permethrin 5 cream)

The images given below show some common arthropods that cause dermatological conditions.

The serpiginous/serpent-like skin lesions seen are cutaneous larva migrans or larva

currens. Ancylostoma duodenale and Necator americanus are hookworms that cause human infection and are least likely to cause cutaneous larva migrans.

Cutaneous larva migrans is caused by non-human hookworms like Ancylostoma

braziliense, Ancylostoma caninum acquired from direct skin contact with soil contaminated by dog or cat feces.

Serpentine or linear single-track lines later mark the course of the larvae as they migrate through the epidermis of the trunk and lower extremities. Symptoms begin to appear within the first two weeks of the patient’s return from a tropical or endemic country. The larval track progresses at approximately 1 cm/h with cutaneous lesions only progressing a few millimeters to a few centimeters daily.

Larva currens aka 'running larva’ of Strongyloidiasis stercoralis. It is known for its distinct rapidity, with the larval track progressing at approximately 0.2 cm/min, with cutaneous lesions progressing up to 10 cm/hour.

Ivermectin is the preferred treatment and is given at 0.15–0.2 mg/kg every day per oral for 1 or 2 days.

A painless and indurated ulcer in a sex worker is characteristic of primary syphilis. It is caused by Treponema pallidum.

Treponema is a corkscrew organism. The coils are very close and regular with around 7 to 8 coils per diameter of a red blood corpuscle. It contains a flagellum and its graceful movements are pathognomonic. It rotates along its long axis and appears to screw slowly forwards and backwards.

Option A: Listeria is a rod-shaped bacterium.

Option C: Helicobacter pylori is spiral or rod-shaped, Gram-negative bacterium. It has two to seven unipolar flagella. It is smaller than spirochetes.

Option D: Leptospira is also spiral and highly motile. They can be distinguished from other spirochetes by their unique question mark hook at the end of the bacterium. It is more tightly wound than Treponema with 18 or more coils per cell.

The given clinical scenario of a painless ulcer with indurated margins is suggestive of primary syphilis. It is Secondary Syphilis that causes non-scarring alopecia that appear as moth-eaten patches if left untreated

The incubation period of syphilis is 9-90 days and varies inversely with the size of the Spirochaete inoculum.

Primary chancre: Painless, indurated, button-like ulcer with painless lymphadenopathy.

Secondary syphilis: Roseolar rash is the earliest sign, but it is hard to see in dark-skinned people. When it fades, it leaves depigmented spots. This is called the necklace of Venus as it commonly occurs around the neck. Generalized papular lesions also occur. Sometimes these papules form a line along the hair margin called Corona Veneris or crown of Venus.

In latent syphilis, there are no features of active disease, but serological tests are positive. It can last up to 20 years.

Tertiary syphilis: Begins with skin nodules or the characteristic gumma which occurs 3-10 years after infection. The name arises from the necrotic center which may turn into a slimy, stringy mass.

The Dory flop sign is described in an uncircumcised male with an indurated lesion of primary syphilis on the underside of the coronal sulcus. Here, prepucial retraction causes the foreskin to flip suddenly. Hence it would only be seen in the middle-aged man with the indurated lesion on his penis.

The Dory flop sign can help distinguish chancres from other nonindurated causes of genital ulcer disease, such as Herpes simplex virus infection and chancroid.

It is named after the movement of a dory, a small wooden fishing boat, which flips suddenly when overturned.

Option A: This young woman has granuloma inguinale, which is a non-indurated lesion. Option C: This circumcised teenager has herpes genitalis.

Option D: Though this lady has an indurated lesion (chancre), the dory flop sign can be demonstrated only in uncircumcised males.

In this patient, a new-onset rash in the setting of syphilis in his partner and a history of a penile ulcer are suggestive of secondary syphilis. A non-infectious maculopapular rash is usually the earliest manifestation.

It usually develops around 8 weeks after initial infection due to generalized treponemal dissemination. Rashes in secondary syphilis have three common features:

• Non-pruritic
• Coppery red color
• Symmetrically distributed

Cutaneous lesions of secondary syphilis are not infectious as they do not have enough treponemes. Exceptions are condyloma lata and mucous patches, which are highly infectious.