A Traditional Chinese Herb Citri Reticulatae Pericarpium Induced Melanonychia.

The common causes for melanonychia include melanoma, repetitive trauma, underlying systemic diseases, onychomycosis, pseudomonas infection and drugs. Drug-induced melanonychia usually affects numerous nails and appears as light brown to black pigmentation on the deck or nail bed with longitudinal, transverse or diffuse distribution. In previous cases, a number of chemotherapeutic agents such as azathioprine, bleomycin sulfate, cyclophosphamide, hydroxyurea and methotrexate were usually linked to melanonychia. Citri reticulatae pericarpium (CRP) is a traditional Chinese herb which is widely used in many foods and health care products in China. Up till now, there were no adverse reactions of CRP reported throughout the literature. Herein, we firstly reported a case of melanonychia in a 67-year-old man caused by CRP for external use.