Pterygium of the Nail - Cutis

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PTERYGIUM OF THE NAILFIGURE 2. Dorsal pterygium involvingone finger after a major trauma.FIGURE 3. Ventral pterygium affectingonly one finger.ually shortens and the nail plate thins until, eventually,the PNF fuses to the matrix and, subsequently,to the nail bed. The resulting nail plate segments progressivelydecrease in size as the pterygium widens,resulting in 2 small remnants involving the PNF.Complete involvement of the matrix and nail bedproduces a total loss of the plate and permanent atrophyof the nail apparatus. Dorsal pterygium is usuallyacquired, but exceptional congenital forms havebeen reported. In a case of nail lichen planus in 1921,Friedman first described pterygium unguis using theterm navellierungsprozess. 1 Dorsal pterygium rarely affectsthe toes; involvement of all 20 toenails has beenreported in only one case.Although pterygium unguis is most commonlycaused by lichen planus (Figure 1), 2 it also may originatefrom burns, radiodermatitis, trauma (Figure 2),and diseases prone to developing adherence bands,including cicatricial pemphigoid, graft versus host disease,toxic epidermal necrolysis, and pemphigus foliaceus(Table I). Peripheral ischemia, intermittentlydetected in Raynaud’s phenomenon 3 or permanentlyfound in atherosclerosis, diabetic vasculopathy, andtype 2 lepra reaction, has been identified as a vascularcause of dorsal pterygium. An idiopathic form ofpterygium unguis, or idiopathic atrophy of the nails,exists, but may be a variation of lichen planus andremains a controversial cause. 4 Congenital forms maybe associated with dyskeratosis congenita, andpterygium formation has been reported in systemiclupus erythematosus and in one case of sarcoidosisinvolving the PNF.Healing of a disease involving the PNF may lead toscarring pterygium formation; however, several factorsthat interfere with the healing of the PNF must appearsimultaneously for this to occur. In patients with dorsalpterygium (excluding the traumatic and congenitaltypes), the main factor is dilatation of the nail capillaryloops and the formation of a slender, microvascularshunt system in them. Although pterygium that344 CUTIS ®
PTERYGIUM OF THE NAILTable I.Causes of Dorsal Pterygium(Pterygium Unguis)AtherosclerosisBurnsCicatricial pemphigoidCongenital etiologyDiabetic vasculopathyDyskeratosis congenitaGraft versus host diseaseIdiopathic atrophy of the nails 3Inadequate corticosteroid matrix infiltration forCandida paronychiaLichen planus 1OnychotillomaniaPemphigus foliaceusRadiodermatitisRaynaud’s phenomenon 3Sarcoidosis involving the PNFSystemic lupus erythematosusToxic epidermal necrolysisTraumaType 2 lepra reactionresults from trauma is not linked to the intensity ofthe trauma, it may be observed in severe distal injury.Also, pterygium remains exceptional in repeatedchronic trauma inflicted to the PNF in onychotillomania,and we observed one pterygium unguis arisingafter inadequate corticosteroid matrix infiltration forCandida paronychia (Richert, unpublished data, 1997).Ventral PterygiumVentral pterygium (Figure 3) is a newly described conditionin which a distal extension of the hyponychiumanchors to the undersurface of the nail plateand, subsequently, obliterates the distal nail groove.The condition was first described in 1973 by Caputoand Prandi, 5 who coined the term pterygium inversumunguis (PIU) to describe a forward extension ofTable II.Causes of Ventral Pterygium(Pterygium Inversum Unguis)Causalgia of the median nerveCongenital etiologyFamily historyFormaldehyde-containing hardeners 8Lenticular atrophy of the palmar creasesLeprosyNeurofibromatosisParesisScarring in the vicinity of the distal nail grooveSubungual exostosisSystemic connective tissue diseasesSystemic lupus erythematosusSystemic sclerosisthe hyponychium anchoring to the undersurface ofthe nail plate and, thus, obliterating the distal nailgroove.PIU may be either congenital or acquired. Odomet al 6 first described the congenital form as a “congenital,painful and aberrant hyponychium” in 1974.In some instances, PIU has been reported as familialand, in most reported cases, patients sought medicaladvice for the pain or bleeding they experiencedwhen trimming their nails. Causes of PIU are listedin Table II.Because the frequency of ventral pterygium maybe underestimated, especially in asymptomatic cases,Mello Filho 7 performed a systematic digital examinationon 2000 patients and found that 0.4% of theadult population was affected. In these cases there wasno family history, and the condition was observedmore frequently in women than in men. Idiopathicforms were preponderant, and involvement of thetoes remains exceptional.Acquired PIU, which occurs in 16% of patients,is by far the most common form and, though idiopathic,is usually secondary to systemic connectivetissue diseases, progressive systemic sclerosis, and systemiclupus erythematosus. One patient with congenitalPIU developed systemic lupus erythematosusat the age of 19, but whether this was coincidentalVOLUME 66, NOVEMBER 2000 345
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