Erythrocyte glucose-6-phosphate dehydrogenase in lichen planus

Cotton et al [1] comparing glucose-6-phosphate dehydrogenase (G-6-PD) activity in biopsies from patients with lichen planus (LP) with that in normal skin suggested that LP might be associated with a congenital abnormality of the enzyme in the skin. Ryan et al. [7] were unable to confirm these results. It is known that individuals with erythrocyte G-6-PD deficiency show a similar decrease of the enzyme in the skin [2] and that skin biopsies can be used to diagnose favizm [3]. The increased incidence of LP in the tropics [6, 8] coincides with the prevalence of erythrocyte G-6-PD deficiency in the same geographical region. The semi-quantitative method of Motulsky did not reveal any difference of erythrocyte G-6-PD activity between patients with LP and control subjects [5]. The present study reports the results obtained with a more sensitive method of erythrocyte G-6-PD determination in a group of Africans with LP. Thirty Nigerian patients with typical clinical picture of LP (23 men and 7 women), aged 15--45 were studied. Control 30 subjects were matched for age, sex and tribe and included persons suffering from scabies and mild pyogenic and superficial mycotic infections. The activity of the erythrocyte G-6-PD was determined at 37 degrees C using the WHO method [9]. Normal values for Northern Nigerians are 1200 +/- 234 mu/1010 red cells. The results (Fig. 1) show a decrease of the erythrocyte G-6-PD activity in patients with lichen planus (P less than 0.01). No relationship between erythrocyte G-6-PD activity and extensiveness, activity or age of onset of the skin lesions was found. The finding of decreased erythrocyte G-6-PD activities in patients with LP in an area where an increased incidence of this skin disease coincides with higher frequency of favizm might suggest a biochemical overlap between these two conditions. Holzmann et al [4] have suggested that the reverse situation of mutual exclusiveness exists between G-6-PD deficiency and psoriasis. In regions with high frequency of G-6-PD defiency psoriasis is uncommon.