Response to Narrow-band UVB – Vitiligo-melasma versus Vitiligo

A Comparative Study

Parikshit Sharma; Harsha S. Pai; Ganesh S. Pai; Maria Kuruvila; Reshma Kolar

Disclosures

Am J Clin Dermatol. 2011;12(2):127-132. 

In This Article

Discussion

Patients with both vitiligo and melasma have a significantly better prognosis for repigmentation on the face and the limbs with NB-UVB treatment; they repigment much earlier compared with patients with vitiligo alone and also achieve a higher level of pigmentation.

Unexpectedly, for truncal lesions, patients in the vitiligo group responded better than those in the vitiligo-melasma group. Although patients in the vitiligo-melasma group started repigmenting earlier, the final extent of pigmentation was greater in the vitiligo group for truncal lesions.

The paradox of faster and more complete repigmentation on the face and limbs but poorer repigmentation on the trunk in the vitiligo-melasma group is difficult to explain. However, the fact that the trunk is not generally exposed to the sun whereas the face and limbs are sun-exposed areas, may explain the faster repigmentation on the face and limbs.

One possible reason for faster and more extensive repigmentation on the face and limbs in patients with vitiligo and melasma is that they have a greater stimulus for repigmentation as they already have hyperactive melanocytes.

Another possibility is the difference in the age groups of the two categories. In our study, the peak onset of vitiligo among patients in the vitiligo-melasma group was between the ages of 41 and 50 years whereas for patients in the vitiligo group it was between the ages of 11 and 20 years. It is possible that patients in their mid-40s have more mature hair follicles (on the face and limbs) after sexual maturity.

We postulate that there may be another factor that alters the melanocyte responsiveness to NB-UVB in the younger patients with vitiligo as compared with the older vitiligo-melasma patients, whereby the melanocytes exhibit a strong sensitivity to NB-UVB.

Biochemical studies of melanocyte enzymes may hold the key to explaining the paradox of facial hyperpigmentation with simultaneous depigmentation occurring in other areas.A better understanding of the pathogenesis may also help to identify more effective treatment modalities in the future.

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