Narrow-Band UVB Therapy — MCQs

10 questions

A nurse got accidental prick from the HIV infected needle. Which of the following statements is false regarding the management of this nurse?

What is the optimal wavelength of light emitted by a Wood's lamp for dermatological examinations?

Contraindications for skin traction: a) Dermatitis b) Vascularly compromised status of limb c) Abrasions d) Hypopigmentation (vitiligo) e) Bony deformity

PUVA therapy is used in all except:

Treatment of choice for Pustular psoriasis is:

Which of the following is the most common side effect of Isotretinoin used for acne vulgaris?

A patient presents with a skin rash that is exaggerated on sun exposure. What is the repair mechanism involved in this condition?

Wood's lamp has a wavelength of –

An 8-year-old girl has extreme photosensitivity since birth. She has recently been diagnosed with skin cancer. What is the diagnosis?

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Which of the following is NOT a complication of PUVA therapy?

Narrow-Band UVB Therapy Indian Medical PG Practice Questions and MCQs

Question 1: A nurse got accidental prick from the HIV infected needle. Which of the following statements is false regarding the management of this nurse?

A. Follow up viral markers of health care personnel should be measured at 6 weeks
B. Zidovudine is used as monotherapy for post-exposure prophylaxis (Correct Answer)
C. Baseline viral markers of health care personnel should be done at the time of presentation
D. Washing hands with soap and water is advised

Explanation: **Zidovudine is used as monotherapy for post-exposure prophylaxis** - **Monotherapy** with zidovudine is **insufficient** for effective **HIV post-exposure prophylaxis (PEP)** due to the high risk of treatment failure and development of drug resistance. - **Current guidelines** recommend a **multi-drug regimen**, typically involving three antiretroviral drugs, for PEP to maximize efficacy against HIV transmission. *Follow up viral markers of health care personnel should be measured at 6 weeks* - **Follow-up viral markers** for HIV, such as **HIV RNA PCR** and **antibody tests**, are routinely measured at specific intervals (e.g., 6 weeks, 3 months, 6 months) to monitor for seroconversion [1]. - This allows for **early detection of HIV infection** if PEP fails, enabling prompt initiation of treatment. *Baseline viral markers of health care personnel should be done at the time of presentation* - Establishing **baseline HIV status** of the healthcare worker at the time of exposure is crucial to differentiate pre-existing infection from a new infection acquired from the needle stick [1]. - This information helps in **interpreting subsequent test results** and guiding further management. *Washing hands with soap and water is advised* - **Immediate washing** of the exposed area with **soap and water** is an important first step in managing a needle stick injury [1]. - This **reduces the viral load** at the site of exposure, minimizing the risk of transmission, although it does not eliminate the need for PEP.

Question 2: What is the optimal wavelength of light emitted by a Wood's lamp for dermatological examinations?

A. 365 nm (Correct Answer)
B. 400 nm
C. 320 nm
D. 200 nm

Explanation: **365 nm** - A Wood's lamp primarily emits **long-wave UVA light** in the 320 to 400 nm range, with an optimal peak around **365 nm**. - This specific wavelength is ideal for inducing **fluorescence** in various dermatological conditions, making them visible. *400 nm* - While within the UVA range, **400 nm** is at the higher end and may not provide the optimal fluorescence yield for all diagnostic purposes compared to 365 nm. - Light at 400 nm is closer to the visible light spectrum and might offer less distinction for subtle fluorescence. *320 nm* - **320 nm** is at the lower end of the UVA spectrum, bordering on UVB. - While still capable of inducing some fluorescence, it is generally less effective than 365 nm for the conditions typically examined with a Wood's lamp. *200 nm* - **200 nm** falls into the **UVC range** (100-280 nm), which is harmful and not used for diagnostic purposes in a Wood's lamp. - This wavelength is absorbed by the atmosphere and epidermis and can cause significant **DNA damage**, making it unsafe for routine dermatological examination.

Question 3: Contraindications for skin traction: a) Dermatitis b) Vascularly compromised status of limb c) Abrasions d) Hypopigmentation (vitiligo) e) Bony deformity

A. ab
B. abc (Correct Answer)
C. acd
D. bcd

Explanation: ***ab*** - All conditions listed under 'a' and 'b' (Dermatitis, Vascularly compromised status of limb, Abrasions) are **absolute contraindications** for skin traction as they directly compromise skin integrity or circulation. - Applying skin traction in these situations can lead to **skin breakdown**, infection, or further **ischemic damage**, worsening the patient's condition. *ab* - While **dermatitis**, **vascular compromise**, and **abrasions** are indeed contraindications, the option for 'abc' implies there might be other correct choices included, which is not the case for this option. - This option is incomplete as it misses 'c' (Abrasions) which is also a significant contraindication. *acd* - This option incorrectly includes **hypopigmentation (vitiligo)** as a contraindication, which does not inherently prevent skin traction. - It also omits **vascularly compromised status of limb**, a critical contraindication, while including 'a', 'c', and 'd'. *bcd* - This option incorrectly includes **hypopigmentation (vitiligo)** as a contraindication for skin traction. - It also omits **dermatitis**, a key contraindication, while including 'b', 'c', and 'd'.

Question 4: PUVA therapy is used in all except:

A. Psoriasis
B. Vitiligo
C. Mycosis fungoides
D. Melasma (Correct Answer)

Explanation: ***Melasma*** - **PUVA (Psoralen plus UVA) therapy** is contraindicated in melasma due to its potential to worsen hyperpigmentation and cause paradoxical darkening. - Melasma is best managed with topical agents like **hydroquinone**, **tretinoin**, and chemical peels, along with strict **sun protection**. *Psoriasis* - **PUVA therapy** is a well-established and effective treatment for moderate to severe psoriasis, especially for patients with widespread plaques. - It works by inhibiting DNA synthesis and cell proliferation in rapidly dividing keratinocytes, leading to a reduction in psoriatic lesions. *Vitiligo* - **PUVA therapy** is a common treatment for vitiligo, stimulating melanocyte activity and promoting repigmentation in affected areas. - Psoralen sensitizes melanocytes to UVA light, which then encourages melanin production. *Mycosis fungoides* - In its early stages, **mycosis fungoides**, a cutaneous T-cell lymphoma, can be effectively treated with **PUVA therapy**. - PUVA induces apoptosis of malignant T-cells in the skin, leading to remission of skin lesions.

Question 5: Treatment of choice for Pustular psoriasis is:

A. Methotrexate (Correct Answer)
B. Psoralen - UV therapy
C. Systemic steroid
D. Estrogen

Explanation: ***Methotrexate*** - **Methotrexate** is a systemic immunosuppressant often considered the first-line treatment for severe forms of **pustular psoriasis** due to its efficacy in reducing inflammation and hyperproliferation of skin cells. - It works by inhibiting **dihydrofolate reductase**, thereby interfering with DNA synthesis and cell division, which is crucial in rapidly dividing cells like those found in psoriasis. *Psoralen - UV therapy* - **Psoralen and ultraviolet A (PUVA)** therapy can be used for chronic plaque psoriasis, but it is generally **contraindicated or used with extreme caution** in pustular psoriasis due to the risk of exacerbating the disease or causing irritation. - **UV light therapy** can sometimes trigger or worsen pustular flares, especially in acute generalized pustular psoriasis. *Systemic steroid* - While systemic steroids can provide temporary relief by addressing inflammation, their use in pustular psoriasis is generally **not recommended for long-term management** due to the high risk of severe rebound flares upon withdrawal. - Withdrawal of **systemic corticosteroids** can precipitate or worsen generalized pustular psoriasis, making them a less desirable long-term treatment option. *Estrogen* - **Estrogen** has no direct role in the treatment of psoriasis. Psoriasis is an inflammatory skin condition, and its pathophysiology is not directly influenced by estrogen levels. - Hormonal therapies are not indicated for the management of psoriasis, including its pustular forms.

Question 6: Which of the following is the most common side effect of Isotretinoin used for acne vulgaris?

A. Xerosis
B. Hair loss
C. Facial erythema
D. Cheilitis (Correct Answer)

Explanation: ***Cheilitis*** - **Cheilitis** (dry, cracked lips) is the most frequently reported side effect due to the drug's effect on sebaceous glands and subsequent reduction in sebum production. - This symptom affects nearly all patients on isotretinoin therapy. *Xerosis* - While **xerosis** (dry skin) is a common side effect of isotretinoin, it is typically less pervasive and severe than cheilitis. - Patients often experience generalized skin dryness, but it usually doesn't affect all patients to the same degree as labial dryness. *Hair loss* - **Hair loss** (alopecia) is a known but less common side effect, usually mild and reversible upon discontinuation of the drug. - It does not affect the majority of patients undergoing isotretinoin treatment. *Facial erythema* - **Facial erythema** (redness) can occur due to skin sensitivity and dryness, but it's not as universal or prominent as cheilitis. - It is more of an indirect effect of the drug, rather than a direct and universal consequence of its mechanism of action.

Question 7: A patient presents with a skin rash that is exaggerated on sun exposure. What is the repair mechanism involved in this condition?

A. Nucleotide excision repair (Correct Answer)
B. Base excision repair
C. Mismatch repair
D. Double stranded DNA break repair

Explanation: ***Nucleotide excision repair*** - This mechanism is responsible for repairing **bulky lesions** in DNA, such as **pyrimidine dimers** caused by **UV radiation** from sun exposure. - Patients with defects in nucleotide excision repair (e.g., **xeroderma pigmentosum**) are highly sensitive to sunlight and develop skin rashes, pigment changes, and skin cancers. *Base excision repair* - This pathway primarily corrects **small damaged bases** that do not cause significant distortion of the DNA helix, such as deaminated, oxidized, or alkylated bases. - It does not primarily address the bulky lesions induced by UV light that cause exaggerated sun sensitivity. *Mismatch repair* - This system corrects errors, like **mismatched base pairs**, that are incorporated during DNA replication. - It is not directly involved in repairing DNA damage caused by environmental factors like UV radiation. *Double stranded DNA break repair* - This mechanism repairs **double-strand breaks** in DNA, which are highly deleterious lesions caused by ionizing radiation or oxidative stress. - While critical for genome stability, it is not the primary repair pathway for UV-induced DNA lesions or the direct cause of sun sensitivity.

Question 8: Wood's lamp has a wavelength of –

A. 320 nm
B. 300 nm
C. 360 nm (Correct Answer)
D. 250 nm

Explanation: ***360 nm*** - A **Wood's lamp** emits **long-wave ultraviolet (UV-A) light**, which is typically in the range of 320 to 450 nm. - The precise wavelength of **360 nm** is the most common and effective for dermatological diagnostic applications, allowing visualization of specific fluorescence patterns. *320 nm* - While 320 nm falls within the UV-A spectrum, it is at the lower end and less characteristic of the peak emission wavelength used in Wood's lamps for diagnostic purposes. - Using this lower wavelength might result in less pronounced or absent fluorescence for some conditions. *300 nm* - A wavelength of 300 nm is in the **UV-B spectrum** which is primarily used for therapeutic purposes like **phototherapy for psoriasis**, not for diagnostic fluorescence with a Wood's lamp. - UV-B light has different biological effects and is too short to elicit the characteristic fluorescence observed with a Wood's lamp. *250 nm* - This wavelength falls into the **UV-C spectrum**, which is **germicidal** and harmful to human tissue. - UV-C light is not used in Wood's lamps for diagnostic purposes due to its damaging properties and inability to produce the desired fluorescence.

Question 9: An 8-year-old girl has extreme photosensitivity since birth. She has recently been diagnosed with skin cancer. What is the diagnosis?

A. Xeroderma Pigmentosum (Correct Answer)
B. Bloom syndrome
C. Griscelli syndrome
D. Chediak Higashi syndrome

Explanation: ***Xeroderma Pigmentosum*** - This condition is characterized by an extreme sensitivity to **ultraviolet (UV) light** from birth due to defects in **DNA repair mechanisms**, leading to severe sunburns, pigmentary changes (freckles, hypopigmented macules), and a high risk of developing **skin cancers** at a young age. - The history of extreme photosensitivity since birth and the diagnosis of skin cancer in an 8-year-old girl is highly indicative of Xeroderma Pigmentosum. *Bloom syndrome* - Bloom syndrome is an inherited disorder characterized by **stunted growth**, a **photosensitive facial rash (telangiectatic erythema)**, and a predisposition to **various cancers**, including leukemia and lymphomas. - While photosensitivity and cancer risk are present, the extreme skin damage and early onset of specific skin cancers (as opposed to leukemias/lymphomas often seen in Bloom) make Xeroderma Pigmentosum a more fitting diagnosis. *Griscelli syndrome* - Griscelli syndrome is a rare autosomal recessive disorder characterized by **partial albinism**, immunodeficiency, and neurological impairment. - While it involves pigmentary abnormalities, it does not typically present with the extreme photosensitivity or the very early skin cancer development described in the patient. *Chediak Higashi syndrome* - Chediak-Higashi syndrome is an autosomal recessive disorder characterized by **partial albinism**, recurrent pyogenic infections, and neurological abnormalities, due to defective lysosomal trafficking. - This syndrome is not primarily associated with extreme photosensitivity leading to early skin cancers but rather with immunodeficiency and neurological issues.

Question 10: Which of the following is NOT a complication of PUVA therapy?

A. Premature aging of the skin
B. Cataracts
C. Skin cancers
D. Exfoliative dermatitis (Correct Answer)

Explanation: **Explanation:** PUVA (Psoralen + Ultraviolet A) therapy involves the administration of a photosensitizer (8-methoxypsoralen) followed by exposure to UVA radiation. While it is an effective treatment for conditions like psoriasis and vitiligo, it carries specific long-term and short-term risks. **Why Exfoliative Dermatitis is the correct answer:** Exfoliative dermatitis (Erythroderma) is **not** a direct complication of PUVA. In fact, PUVA is often used as a *treatment* modality for certain types of exfoliative dermatitis, such as those caused by Mycosis Fungoides or Psoriasis. While PUVA can cause a "PUVA itch" or a phototoxic burn (erythema), it does not typically trigger generalized exfoliation. **Analysis of Incorrect Options:** * **Premature aging of the skin (Dermatoheliosis):** Chronic UVA exposure leads to the degradation of collagen and elastin fibers, resulting in wrinkles, lentigines, and telangiectasia. * **Cataracts:** Psoralens distribute to the lens of the eye. If the eyes are not protected with UVA-blocking sunglasses for 24 hours post-ingestion, UVA exposure can lead to lens opacification. * **Skin cancers:** PUVA is mutagenic. Long-term therapy significantly increases the risk of Non-Melanoma Skin Cancers (NMSC), particularly **Squamous Cell Carcinoma (SCC)**. **High-Yield Clinical Pearls for NEET-PG:** * **Most common acute side effect:** Erythema (phototoxicity) and pruritus. * **Most common long-term risk:** Squamous Cell Carcinoma (SCC) is more common than Basal Cell Carcinoma (BCC) in PUVA patients (reversing the usual ratio). * **PUVA Lentigines:** Distinctive, irregular pigmented macules that appear after chronic therapy. * **Contraindications:** Pregnancy, lactation, history of skin cancer (Xeroderma Pigmentosum), and severe hepatic/renal failure.

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