Background/Purpose: Photosensitivity (PS) is one of the most common manifestations of systemic lupus erythematosus (SLE), and is 1 of only 11 criteria used to make the diagnosis of SLE.  However, the definition of photosensitivity is vague and its pathophysiology is not well understood.  There is a need to better define the clinical aspects of photosensitivity in lupus, to enhance further study of this difficult problem.  The objective of this study was to characterize self-reported photosensitivity phenotypes among a primarily cutaneous lupus (CLE) population.

Methods:  A novel photosensitivity questionnaire provided a framework for characterizing subjects’ experience of sun sensitivity.  The PS questionnaire was based on information gathered over a 9-month period of subject interviews pertaining to sun exposure.  Recurring themes of self-reported photosensitivity relating to morphology, characteristics, and timing of reactions were identified and incorporated into a brief PS questionnaire. The PS questionnaire was used to classify subject responses into five PS phenotypes: sun-induced CLE exacerbation (directCLE); general worsening of CLE in summer (genCLE); PMLE-like reactions (genSkin); general pruritus/paresthesia (genRxn); and systemic symptoms, e.g. headache, arthralgia (genSys).  100 subjects with CLE alone or both CLE and SLE were interviewed.

Results:  83% of subjects ascribed to any and 66% reported more than one PS phenotype.  47% cited direct examples of sun-induced CLE [directCLE].  Other PS phenotypes were reported as follows: 22% genCLE, 38% genSkin, 36% genRxn, and 37% genSys.  The genSys phenotype was reported by fewer discoid and subacute cutaneous LE compared with acute and tumid LE subjects, X²=13.0, p<0.05. Subjects with both CLE and SLE reported more paresthesias/pruritus (51% vs 23%) and systemic symptoms (50% vs 26%) compared to those without SLE, p<0.05. Subjects with PMLE-like reactions had lower CLE Disease Area and Severity Index (CLASI) activity scores compared to other PS phenotypes (6.4±5.4 vs 11.5±11.11, p=0.02).

Conclusion:  Self-reported photosensitivity in lupus ranges from CLE-specific reactions to generalized cutaneous eruptions to systemic symptoms.  Clinical PS phenotypes are associated with CLE subtype, SLE diagnosis, and CLASI activity scores.  Recognition of various PS phenotypes in CLE will permit improved definitions of clinical photosensitivity and allow for more precise investigation into the pathophysiology of photosensitivity in lupus.