Progressive macular hypomelanosis (PMH) treatable but often misdiagnosed

The results of the studies presented in this thesis confirm the opinion that PMH is a separate, treatable and relatively new entity, which if the right diagnostic tests are performed can easily be distinguished from other hypopigmented skin disorders. Although the precise pathogenesis is still unknown, we gained more insight and gave a more accurate description of PMH. The investigations demonstrating the relation between Propioni bacteria and PMH provide the strongest evidence in confirming the idea that it is a separate entity. We propose that the clinical characteristics of PMH in combination with red, follicular fluorescence in lesional skin and/or gram-positive bacteria with a rod-like structure in the pilosebaceous glands of lesional skin, should be considered as diagnostic criteria for PMH. It is obvious that further research is necessary, for instance to consolidate the diagnostic criteria, to develop additional treatment modalities and to identify the postulated factor that is produced by the bacteria, influencing melanogenesis.