logo Phototherapy key points test

Scaly skin diseases

Phototherapy key points test

Phototherapy in dermatology refers to: # Treatment using UVC #! Treatment using UVB #! Treatment using UVA # Treatment using Infrared radiation Explanation: Phototherapy in dermatology refers to UVB or PUVA (psoralen and UVA). Photochemotherapy refers to: # Treatment using cytotoxic agents and UV radiation #! Treatment using Psoralens and UVA #! Treatment using Psoralens and UVB # Treatment using UVA alone Explanation: Photochemotherapy refers to the combination of psoralens and phototherapy with UVA (PUVA) or less commonly, UVB (PUVB). In New Zealand, phototherapy is delivered using which of the following lamps? #! Low pressure mercury discharge lamps # High pressure mercury discharge lamps # Tungsten halide lamps # Halogen lamps Explanation: Phototherapy is most often delivered using low-pressure mercury discharge lamps. However halogen lamps are in use in Europe and elsewhere. Which of the following statements is correct for psoriasis? #! NB-UVB is more effective than BB-UVB # NB-UVB is more effective than PUVA #! PUVA is more effective than NB-UVB # BB-UVB is more effective than PUVA Explanation: There are individuals with idiosyncratic responses but the majority of patients with psoriasis get the best results from PUVA. However this is less convenient and more toxic than UVB, which is therefore used more frequently. Narrowband (NB) UVB (311 nm) is more effective than broadband (BB) UVB (290-320 nm). Mechanisms of action of phototherapy or photochemotherapy on skin diseases includes: #! Immune suppression #! Reduction in keratinocyte proliferation #! Effects on endothelial cells #! Effects on fibroblasts Explanation: Phototherapy and phototherapy probably primarily influence skin diseases because of their immune suppressive action but ultraviolet radiation has direct effects on cellular DNA and cytoplasmic components of the structural components of skin. Contraindications to phototherapy include: #! Skin type 1 (burns easily, does not tan) #! Photosensitivity # Concomitant oral steroids #! History of melanoma Explanation: Phototherapy is relatively unsuitable for patients who are very fair skinned because it may be difficult to deliver a high enough dose to influence the skin disease without severe adverse effects. Phototherapy may be used to treat photosensitivity but in general photosensitivity is a contraindication to treatment. It is unwise to treat very sun damaged patients or those with a recent history of melanoma because of the immune suppressive effects of treatment and the known association of ultraviolet radiation with skin cancers. Which of the following statements is true? # UVB treatment is usually delivered once weekly #! PUVA treatment is usually two or three times weekly # 90% psoriasis clears with NB-UVB # Squamous cell carcinoma is ten times more likely after 20 PUVA treatments Explanation: Phototherapy and photochemotherapy are generally ineffective if delivered less frequently than two or three times a week, although some patients receive once-weekly maintenance PUVA treatments to reduce the chance of relapse. 75% patients with psoriasis clear or nearly clear with NB-UVB and a slightly greater percentage clear with PUVA.