Department of Rheumatology, University Hospital of Umeå, 901 85 Umeå, Sweden
SIR, Exposure to the ultraviolet (UV) radiation of sunlight may induce disease flares with extracutaneous manifestations in systemic lupus erythematosus (SLE) [1]. There is only one previous report on UV-induced neurological manifestations in SLE [2]. Here the case is presented of a 49-yr-old Caucasian female who suffered two episodes of UV-induced optic neuritis.
In April 1997, the patient presented with deteriorating vision in her right eye, proceeding to blindness within 2 weeks (Fig. 1). The ophthalmologist found lack of vision in the upper half of the vision field, ability to count fingers only at 20 cm distance in the lower half and lack of colour vision. The papill was swollen with blurred margins. After 1 week on 60 mg prednisolone, the patient regained almost normal vision. For half a year, however, the papill remained slightly swollen and the field of vision slightly concentrically restricted in the upper part. In May 1995, the patient had experienced decreased vision and lightning phenomenon in her left eye. Vision and fundoscopy were normal; perimetry was not performed. Only after half a year, the patient recovered spontaneously. Both incidents occurred 1 week after returning from a 2-week-long ski-ing holiday to Arjeplog, northern Sweden (66°N, 18°E, 7800 m above sea level). Sunshine, which always made the patient feel dizzy with nausea and fatigue, was difficult to avoid, since she enjoyed taking holidays with family members. The patient's mother had suffered from juvenile diabetes mellitus since the age of 23 yr. The patient herself had been treated with levothyroxine for 2 yr because of a slight hypothyreosis.
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The highest ozone depletion rate of the hemisphere, accentuated by frequent sudden ozone losses in springtime, intensifies the UV-B radiation in the mountains of Northern Sweden. UV-B is further enhanced by height over sea level and reflection from snow. All gases in the atmosphere attenuate UV-B by scattering, corresponding to an 8% increase per kilometre above sea level. Dependent on quality, snow reflects UV-B, which may increase by 2035% [3].
The UV radiation of sunlight is generally divided into UV-C (200290 nm: far UV, germicidal UV), UV-B (290320 nm: midrange UV, sunburn radiation) and UV-A (320400 nm: near UV, black light). UV-C radiation is totally, and UV-B partially, absorbed by the stratospheric ozone layer. While UV-B does not penetrate window glass and only reaches the epidermis, UV-A penetrates average, but not tinted glass, and the epidermis [4, 5]. UV-B in small doses causes DNA damage, lymphocyte apoptosis [6], and induction of pro-inflammatory cytokines, adhesion molecules [4] and nitric oxide synthase [7] in keratinocytes. This may even have systemic effects. The UV-B-induced change of trans- to cis-urocanoic acid suppresses cell-mediated immunity. Moreover, UV-B decreases the ability of Langerhans cells to stimulate CD4+ Th1 cells and activates CD4+CD45RA+ suppressor-inducer T cells, probably changing the immunological scene in favour of B-cell activation [4, 8]. UV-A may provoke systemic flares directly by penetrating into the subcutis vasculature. On the other hand, longer wavelength UV light, i.e. UV-A1 (340400 nm), may have flare-preventing effects in SLE [9].
The only characteristic of SLE in the present patient was a high-titre ANA. However, optic neuritis might be the debuting symptom in SLE [10]. The only report on UV-induced CNS lupus is that of a Swedish female SLE patient, suffering two attacks of myelitis after a vacation to the Balearics [2]. Optic neuritis is often combined with myelitis in SLE, a combination named Devic's opticomyelitis. The manifestations constituting Devic's syndrome might thus be more easily inducible by UV light than other CNS manifestations in SLE.
Generally, there are several ways to avoid UV radiation: use of sunscreens, tinted car windows [5], avoidance of cool, white, fluorescent light. Moreover, thanks to the Montreal protocol, it is hoped that the ozone depletion rate will decrease [3].
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