简介：AbstractIntroduction:Pterygium inversum unguis (PIU) refers to a disorder that distal portion of the nail bed adheres to ventral surface of the nail plate, leading to the absence of the distal groove. This is not a common condition in existing literature, thus its pathogenesis has not been elucidated. The occurrence can be congenital, idiopathic, or secondary. Here we present a case of PIU associated with systemic lupus erythematosus (SLE).Case presentation:A 33-year-old woman presented with distal nail bed of the bilateral fingers (excluding the thumbs) adheres to the ventral surface of the nail plate, associated with a malar rash, photosensitivity, and arthritis, whose further laboratory examinations confirmed immunologic disorders. All these clinical characteristics and laboratory results point to the diagnosis of PIU secondary to SLE. Treatment of SLE and topical application of tretinoin 0.025% were performed and resulted in the improvement of most discomforts but PIU. There has no aggravation or alleviation of the PIU during a year of follow-up.Discussion:Acquired form of PIU is reportedly associated with connective tissue diseases or other conditions, which may be caused by abnormal distal circulation or exposure to certain chemical stimuli. Some therapies may be available, while the most effective strategy is to treat potential disorder. Clinicians should be vigilant to find out the underlying causes of PIU, so as to obtain better therapeutic efficacy.Conclusion:We observed a rare disorder of PIU associated with SLE. Hence when identifying a patient of PIU, comprehensive evaluations and long-term follow-up are imperative to to detect the development of connective tissus diseases, such as SLE.