Low-dose UV-therapy: effectivity and safety aspects
Authors:   , Franken Sylvie Mireille 
Published: January 2023

This thesis investigated the effectivity and safety of low-dose phototherapy in the
treatment of skin diseases. The current individualised, “on demand society” creates the
need for treatment in the patients’ home at a time point that suits the patient best. But
little was known on safety and effectivity of low-dose UV-treatment. This thesis is
comprised
of three parts:
1. A review of the literature to understand what the hurdles are in prescription of phototherapy,
2. Investigating the effectivity of low-dose home-based phototherapy,
3. Investigating the potential carcinogenic risk of low-dose home based phototherapy.

Conclusion and recommendations
Low-dose phototherapy is an effective treatment in patients with PLE and mild to moderate
psoriasis. PLE patients were more satisfied with the low-dose home based treatment than
conventional treatment. Low-dose phototherapy could be given continuously and patients
are less limited in planning their activities, which might improve quality of life.
For psoriasis patients with mild to moderate complaints low-dose phototherapy might
help patients who are tired of the frequent ointment applications or in need of an adjuvant
with their corticosteroid therapies. Prolonged treatment up to 18 months appears safe,
although further studies are needed to corroborate this and provide more evidence about
the effects in even longer time intervals. In these studies it would be relevant to also
ascertain the presence of p53 mutations in the epidermis. As skin malignancies can
develop after years of chronic UV-exposure it would be wise to advocate for regular skin
check-ups for patients undergoing this treatment. An electronic monitoring would be
advisable to corroborate the adherence to treatment protocol, although the results of the
present study suggest that there is no major reason for concern. This is in line with the
results of prior studies. Dermatologists should, however, stay on their toes about
development of “tanorexia” which could place a patient at risk for skin cancer. Tanorexia
is reported to be caused by the release of β-endorphins by UV light. Not all patients
exposed to UV-light develop tanorexia however. There probably are other factors playing
a part in the development of this addiction.
It is shown in this thesis that low-dose phototherapy is effective in PLE and psoriasis; it is
probable that this therapy might be relevant for other inflammatory skin diseases, such as
atopic dermatitis, vitiligo or graft versus host disease. Further studies to demonstrate
effectiveness and safety of a home-based low-dose phototherapy in other diseases are
warranted.
Another interesting aspect of the low-dose home-based phototherapy is the rise in vitamin
D. If low-dose phototherapy is confirmed to be safe, it would be an interesting option to
use this device in patients with or at risk for hypovitaminosis D, such as dialysis patients
who also often deal with uremic pruritus. Other patients that could benefit from this are
elderly who are at risk for bone fractures, or patients with chronic pain associated with
vitamin D deficiency. Prior studies have demonstrated that patients with hypovitaminosis
D use more opiates, than patients with normal vitamin D levels. It might be interesting to
investigate the effect of low-dose UV in patients with chronic pain requiring opiates with
and without hypovitaminosis D. Could low-dose phototherapy lessen their pain use of
opioids? And is this effect due to the stimulation of β-endorphins or is it the result of
normalisation of vitamin D levels?
To recapitulate: if low-dose phototherapy is confirmed to be safe in prolonged treatment,
it might provide a valuable tool in the treatment not only dermatological diseases, but also
various internal diseases.