Pterygium Inversum Unguis: Report of an Extensive Case With Good Therapeutic Response to Hydroxypropyl Chitosan and Review of the Literature

March 2013 | Volume 12 | Issue 3 | Case Reports | 344 | Copyright © March 2013

Roberta Marinho Falcão Gondim MD PhD,a,b Pedro Bezerra da Trindade Neto MD PhD,a and Robert Baran MDc

aDepartment of Dermatology, Universidade Federal do Rio Grande do Norte, Natal-RN, Brazil bFaculdade de Medicina da Universidade Potiguar, Natal-RN, Brazil cNail Disease Center, Cannes, France

Pterygium inversum unguis is a rare but not exceptional dermatological condition, with few descriptions in literature. It occurs more frequently in females and may be associated with several clinical conditions. About 50% of cases are concurrent with collagen diseases such as systemic lupus erythematosus and scleroderma. Severe cases are accompanied by moderate morbidity caused by discomfort when the patient has to perform minor tasks. The treatment has been considered complex, regardless of its underlying cause, with poor response to the topical therapies such as keratolytics and corticosteroids. This paper reports a case of pterygium inversum unguis with a good therapeutic response to hydroxypropyl chitosan and includes a review of the literature.

J Drugs Dermatol. 2013;12(3):344-346.


A 32-year-old woman presented with pain, discomfort, and bleeding when she clipped her nails. She had no other symptoms or skin lesions. The condition had been present for 4 years, and she had refused any treatment previously. On examination, a forward extension of the hyponychium was adherent to the ventral aspect of the nail plate. The condition involved all nails on both hands and spared the toenails (Figure 1). There was no relevant family history.
A treatment recently used for psoriatic nail dystrophy1 was initiated with once-daily application of a water-soluble nail lacquer containing hydroxypropyl chitosan, horsetail extract (Equisetum arvense), and methylsulfonylmethane. After 2 months of the daily treatment, examination revealed considerable improvement in the nail changes (Figure 2). After 4 months of treatment, there was an overall improvement in the condition, but with some persistence of the lesion on the third fingernail.


Pterygium inversum unguis (PIU) is a disorder consisting of a forward extension of the hyponychium (a subungual structure distal to the nail bed) anchoring to the undersurface of the nail plate and thus obliterating the distal nail groove. It may affect a single finger or multiple fingers, as shown in this case. PIU may be congenital and/or familial, or acquired.
PIU was first described in 1973 by Caputo and Prandi,2 in a female patient who presented with ventral pterygium in multiple fingers of the hands, with no apparent cause, similar to the case described in our paper. Since then, some cases have been described as related to systemic diseases, principally including collagen diseases,3,4 allergic dermatitis,5,6 neurofibromatosis, hemiparesis (due to stroke),7 subungual exostosis,8 and leprosy.9 A congenital type was first described by Odom et al.10 The causes of PIU (ventral pterygium) are summarized in Table 1. 2,4-6,8-9,11-18
Women are more frequently affected than men, with ages ranging between 20 and 70 years. The most common complaints are pain and bleeding occurring on clipping the nails.19 In about 50% of cases there is a history of associated collagen disease. In addition, in some cases, there is a family history of the condition. 12,13,16,18,20,21 Sometimes the condition is idiopathic.14
Hand nails are more often affected than foot nails with a predominance of spontaneous cases. Because of its rarity, the appropriate mechanism of origin is speculative,7,19 but blood alterations and ischemia are the most acceptable hypotheses.7 A similar mechanism has been considered in patients with leprosy.9 Peripheral vascular and sensorineural alterations were suggested as genesis of morbidity in a case report associated with stroke.7
On physical examination of these patients, it is possible to verify that there is a thick layer of keratin between the hyponychium and the ventral face of the nail plate.14 This is histologically corroborated with an intense hyperkeratosis tightly fixed to the nail