Pterygium Complicating Nail Psoriasis and Trachyonychia: Is It Rare?

Abstract

Pterygium is an irreversible scarring of the nail matrix resulting in a split nail. The deformity is most often post-traumatic, though it can be the end result of aggressive inflammatory diseases involving the nail matrix like nail lichen planus, graft versus host disease, or autoimmune bullous disorders like cicatricial pemphigoid. It is thought to be a result of lymphocytic inflammation-mediated damage to the nail matrix, initiating a fibrotic process which slowly fuses the nail fold with the nail matrix and bed, destroying the nail plate. We report an interesting observation in a series of patients of various ages with nail and/or skin psoriasis, and trachyonychia associated with pterygium formation in multiple nails. Insidious progression to anonychia was also observed despite initiating adequate treatment. This report highlights the potential of irreversible nail damage occurring in reportedly benign nail conditions like psoriasis and trachyonychia, emphasizing the need for early recognition and aggressive management in such cases.

Established Facts

• Dorsal pterygium is an irreversible nail deformity known to be associated most commonly with trauma, though also with dermatoses affecting the nail matrix like lichen planus, graft versus host disease, or autoimmune bullous disorders.

• Disorders like nail psoriasis and trachyonychia are not known to cause irreversible damage to nails like pterygium or anonychia.

Novel Insights

• Irreversible damage to the matrix can result from a wider spectrum of inflammatory nail disease, than previously recognized.

• Pterygium can occur in apparently benign nail disorders like nail psoriasis and trachyonychia, though uncommonly.

Introduction

Dorsal pterygium or pterygium unguis is an abnormality of the nail unit, which is most commonly acquired in nature. It refers to a “wing-shaped” cutaneous fold arising from the proximal nail fold (PNF) that fuses with the nail matrix and then the nail bed, thus splitting the nail plate into 2 lateral segments [1, 2, 3]. This fold may subsequently widen, leading to further narrowing of the lateral nail segments and ultimately total loss of nail plate (anonychia) [2, 3].

Pterygium was first described by Friedman (1921) in a case of nail lichen planus, which still remains its most frequent and well-recognized inflammatory etiology [4]. However, many other causes have been described which have been summarized in Table 1 [1, 2, 3]. Idiopathic atrophy of nails refers to pterygium developing in multiple nails when no obvious cause or inflammation is seen; however, Tosti et al. [5] described this as a possible variant of lichen planus, differing from pterygium by the fact that the PNF is preserved in this entity.

Table 1.

Causes of dorsal pterygium involving the nail unit

Traumatic causes	Acute trauma: burns, penetrating injury, radiodermatitis, split nail deformity
	Chronic trauma: onychotillomania
Dermatological diseases	Lichen planus (involving the nail matrix)
	Toxic epidermal necrolysis
	Porokeratosis of Mibelli
Bullous diseases	Autoimmune bullous diseases: cicatricial pemphigoid, pemphigus foliaceus, pemphigus vulgaris, etc.
	Mechanobullous diseases: epidermolysis bullosa (various variants)
	Bullous drug reactions with scarring
Infections	Purulent infections
	Leprosy (neuropathic damage or secondary purulent infections)
Genodermatoses	Dyskeratosis congenita
	Marfan syndrome
Nail tumors	Onychomatricoma (matrix metaplasia of the ventral aspect of PNF)
Systemic disease	Graft versus host disease
	Systemic lupus erythematosus
	Sarcoidosis (involving the PNF)
Vascular causes	Raynaud's phenomenon
	Atherosclerosis
	Diabetic vasculopathy
	Type 2 lepra reaction
Idiopathic pterygium

PNF, proximal nail fold.

To the best of our knowledge, disorders like trachyonychia and nail psoriasis have not been associated with pterygium formation. Hence, they have been considered as benign nail diseases where the need for biopsy or aggressive management is questioned in contrast to nail lichen planus. We present a series of 7 cases with skin and/or nail psoriasis and trachyonychia with pterygium formation.

Case Reports

We report 7 patients (5 females and 2 males) with nail psoriasis (4 patients) or trachyonychia (3 patients) with age ranging from 8 to 62 years. The individual case details are summarized in Table 2. Most of the patients were young (8–17 years) (Fig. 1, 2, 3, 4, 5) though older patients (45 and 62 years) (Fig. 6, 7) were also seen. All patients denied any history of nail manipulation, biting, trauma, drug reaction, or any preceding bullous lesions. None of the patients had any evidence of peripheral ischemic or neuropathic changes. Suggestive skin lesions of psoriasis were present in 3 cases (Fig. 5, 6, 7) while 3 patients never had any skin lesions. Two patients developed subsequent hair loss suggestive of alopecia areata on follow-up (cases 3 and 5) (Fig. 3). Nail biopsy done from 4 cases confirmed nail psoriasis with a prominent neutrophilic infiltrate and hypergranulosis. Nail biopsy was not done in rest of the 3 cases as the diagnosis was confirmed on skin biopsy (2 cases) or parents did not consent for a nail biopsy (1 patient). The histopathological details are also summarized in Table 2.

Table 2.

Characteristics of patients with nail psoriasis or trachyonychia developing pterygium

S. No.	Age/sex	Nail lesions	Skin lesions	Skin histopathology	Nail histopathology	Pterygium
1	15/F	Asymptomatic progressive thickening and discoloration of all 20 nails (2-year duration) Pachyonychia, prominent distal onycholysis and subungual hyperkeratosis (nail psoriasis) Additional surface irregularities in toenails (Fig. 1)	Nil	−	Prominent neutrophilic infiltrate with an absence of granular layer or any fungal elements, confirming the diagnosis of nail psoriasis	Two toenails (Fig. 1)
2	8/F	Asymptomatic nail changes (1 year) with slowly more nails getting involved (Fig. 2a–c) Roughening, longitudinal ridging, and thinning of nails (trachyonychia) Waxing and waning course Similar nail changes in younger brother over 2–3 months, seen as shiny trachyonychia	Nil	−	Not done in view of age and mild changes	Left ring fingernail Right thumb nail (Fig. 2b, c)
3	14/F	Asymptomatic nail changes (1.5 years) Roughening, thinning (trachyonychia) and splitting of fingernails (Fig. 3a, b) Fine pits with minimal longitudinal ridging involving few fingernails The patient was started on intramatricial triamcinolone injections at monthly intervals	Alopecia areata (Fig. 3c)	−	Biopsy from middle fingernail showed the presence of a prominent neutrophilic infiltrate involving the epithelium, suggestive of nail psoriasis	Left thumbnail Left index fingernail
4	62/M	Erythema, scaling, and loss of multiple nails (Fig. 6a, b) Significant erythema involving nail bed and the periungual skin (nail psoriasis) (Fig. 6a, b) Pustulation, scaling, and thinning with loss of multiple nails Onychoscopy showed prominent, dilated, and tortuous longitudinal nail fold capillaries and glomerular nail bed capillaries (Fig. 6c)	Psoriasis vulgaris on systemic therapy	−	Nail biopsy confirmed the diagnosis of nail psoriasis with marked neutrophilic infiltrate and hypergranulosis	Anonychia and pterygium involving multiple fingernails and toenails
5	17/F	Asymptomatic toenail changes (1.5 years) (Fig. 4b) Thinning and ridging of multiple toenails with partial nail destruction (nail psoriasis)	Psoriasis vulgaris − shins, elbows, and trunk (Fig. 4a) + Alopecia areata (ophiasis and patchy)	Changes compatible with psoriasis vulgaris	Not done	Pterygium involving multiple toenails (Fig. 4b)
6	45/F	Asymptomatic progressive thickening and discoloration of all 20 nails (2 years) Changes more marked in fingernails Distal onycholysis and subungual hyperkeratosis (nail psoriasis)	Plaque psoriasis − shins and elbows, lower back	Changes compatible with psoriasis vulgaris	Not done	Pterygium involving multiple toenails (Fig. 7)
7	17/M	Asymptomatic roughening of nails (1.5-year duration) Longitudinal ridging, with dry and lustreless nails Both finger and toenails (with more marked changes in fingers)	Nil	−	Nail plate and nail bed biopsy showed changes compatible with nail psoriasis with a prominent neutrophilic infiltrate	Pterygium involving multiple toenails (Fig. 7)

Fig. 1.

Patient 1 with nail psoriasis. Toenails show thickening, discoloration, distal onycholysis, and prominent surface changes with pterygium involving the right great toenail and left 2nd toenail (black arrows).

Fig. 2.

a Patient 2 with roughening, longitudinal ridging, and thinning involving fingernails, suggestive of shiny trachyonychia. b Pterygium can be seen in left ring finger nail and right thumb.

Fig. 3.

a–c Patient 3 with nail pitting, roughened appearance, pterygium formation, and alopecia areata (c).

Fig. 4.

a–c Patient 4 with extensive periungual and nail psoriasis with pterygium and anonychia involving multiple nails. There is extensive erythema, scaling and thinning or loss of multiple finger nails (a, b) and toenails. The highlighted nails (black arrows) show pterygium formation with fusion of proximal nail fold and nail bed. There is significant erythema and scaling involving the periungual skin. Onychoscopic examination of one of the nails (c) shows dilated and tortuous proximal nail fold capillaries (black arrow) with red dots suggestive of glomerular dilated capillaries in the exposed nail bed (blue arrow). Dinolite AM7115MZT, polarizing, ×180.

Fig. 5.

a, b Patient 5 with skin lesions suggestive of psoriasis (a) and nail changes with multiple pterygium formation (b).

Fig. 6.

Patient 6 with thickening and discoloration of multiple nails and pterygium involving toenails.

Fig. 7.

a, b Patient 7 with pterygium involving multiple fingernails.

Discussion/Conclusion

Pterygium involves fingernails more often than toenails. It involves selective nails more commonly, though involvement of all 20 nails has also been reported. Various etiological factors have been implicated as discussed above; however, nail psoriasis or trachyonychia has not been implicated as a cause of pterygium to the best of our knowledge. In general, trachyonychia is proposed to be a benign disease with no potential for scarring, hence not warranting biopsy or aggressive management [6]. However, our experience suggests that there might be a subset of cases which may indeed develop irreversible changes.

The pathogenesis of pterygium is complex and inadequately understood. It has been suggested to be a result of lymphocyte-mediated destruction of the nail unit [2]. Contrary to this popularly held concept, all our patients biopsied showed a neutrophilic infiltrate in their nail biopsies. Bonifazi et al. [7] suggested that pterygium results from a violent inflammation resulting in a fibrotic process which leads to fusion of the nail fold with the bed. This fibrosis prevents the normal growth of the nail plate, which then appears split or is completely destroyed. However, in 2 of our patients, the inflammation was clinically minimal, with no aggressive signs preceding the insidious development of pterygia.

Baran et al. [1, 3] proposed that several coincident factors are required to produce a pterygium; the most conspicuous being the dilation of nail capillary loops, which lead to production of a slender microvascular shunt system within the dilated loops. As dilation of capillary loops is the main histopathological feature of psoriasis in general and nail psoriasis in particular, it could explain the development of pterygium in nail psoriasis, even though pterygium is not a common clinical outcome. Pterygium formation is also proposed to be the result of healing of a disease involving the PNF [3]. As disorders like LP preferentially involve the PNF (and underlying matrix), there is a higher risk of pterygium formation in these disorders. In fact, if not promptly recognized and treated, nail LP has a high potential to cause scarring and pterygium formation [8, 9]. We could offer a similar explanation for case 4, where psoriatic lesions were particularly severe over the nail folds and the nail bed, explaining the development of pterygium and anonychia in multiple nails.

Trauma has also been implicated in the pathogenesis of pterygium. Trauma is also a major inciting factor for Koebner's phenomenon known to occur in psoriasis. However, there is minimal if any correlation between the development of pterygium and the severity or intensity of injury [1, 3]. Severe distal trauma is proposed to be responsible for most cases of post-traumatic pterygium, whereas chronic, repetitive, proximal trauma like onychotillomania does not often result in pterygium formation [10]. In our experience, a similar premise may hold true for matrix inflammation as well with the severity of matrix inflammation not being a sensitive marker of the future risk of pterygium formation. All our patients denied history of acute or chronic trauma and developed pterygium in the absence of severe inflammation (except 1 case). Nevertheless, the role of chronic repetitive trauma in inciting Koebner's phenomenon in cases with nail psoriasis, which could rarely result in pterygium formation, cannot be ruled out. Pterygium has also been reported after Candida paronychia treated with intramatricial steroid therapy [1].

To conclude, though trachyonychia and nail psoriasis are perceived as non-scarring nail diseases, our experience suggests that there is a distinct potential for the development of pterygium (or even anonychia) in both the entities. As the intensity of PNF and matricial inflammation may not be a reliable marker for this risk, we need to be more vigilant and proactive in their management to prevent such unfortunate outcomes. Future reports in this direction may help quantitate the magnitude or identify predisposing factors.

Statement of Ethics

A written informed consent for publication was taken of this case report and any accompanying images, from all the study participants (aged 18 years and above) and from their parents or legal guardian (in case of minors) after explaining the disease process and management involved. The research work complies with the guidelines for human studies. The research was conducted ethically in accordance with the World Medical Association Declaration of Helsinki.

Conflict of Interest Statement

We, the authors (Dr. Chander Grover, Dr. Archana Singal, and Dr. SN Bhattacharya), have no conflicts of interest to declare.

Funding Sources

The authors did not receive any funding.

Author Contributions

Chander Grover: concept, study design, patient recruitment, treatment and follow-up, record maintenance, literature search, and manuscript writing and revisions. Archana Singal: study design, patient recruitment, treatment and follow-up, record maintenance, and manuscript writing. S.N. Bhattacharya: study design, patient recruitment, treatment, and follow-up.