Photosensitivity is an important characteristic feature of several forms of
lupus erythematosus (LE), and induction of skin lesions by UV-A and UV-B i
rradiation has been proved to be an optimal model for evaluating light sens
itivity in patients with this disease. Because lupus erythematosus tumidus
(LET) has rarely been documented in the literature and is often difficult t
o differentiate from other photodermatoses such as polymorphous light erupt
ion, we performed photoprovocation tests in 60 patients with LET according
to a standardized protocol. Areas of uninvolved skin on the upper back were
irradiated with single doses of UV-A (100 J/cm(2)) and/or UV-B (1.5 minima
l erythema dose) daily for three consecutive days. Interestingly, patients
with LET are more photosensitive than those with subacute cutaneous lupus e
rythematosus, and in our study experimental phototesting revealed character
istic skin lesions in 43 patients (72%), Because of the latency period in d
eveloping positive phototest reactions, it might be difficult for these pat
ients to link sun exposure with their skin lesions. Furthermore, our data r
evealed a positive correlation of antinuclear antibodies and positive provo
cative phototest reactions in these patients as seen for other forms of LE,
In conclusion, the high incidence of positive phototest reactions in corre
lation with the clinical findings, history of photosensitivity and antinucl
ear antibodies enable the classification of LET as the most photosensitive
type of LE.