Severe Lichen Planus Pigmentosus Inversus in an Elderly Female Following Intra-Articular Injections of Homeopathic Substances

This case report details an 80-year-old woman who developed severe Lichen Planus Pigmentosus Inversus (LIPPI) after receiving intra-articular injections of the homeopathic preparation Zeel comp. N for knee pain. The patient showed sharply demarcated, reticulated brownish-grey hyperpigmentation in flexural areas, confirmed by histopathology. Although the timing suggests a possible trigger from the injections, causality is uncertain, as indicated by a Naranjo score suggesting only a possible adverse drug reaction and negative prick and patch tests. Treatment with systemic corticosteroids, acitretin, and topical tacrolimus improved pruritus but not hyperpigmentation. The case underscores the need for cautious interpretation of biologically active compounds as potential triggers for LIPPI and calls for further research.