Congenital malalignment of the great toenails

What is congenital malalignment of the great toenails?

Congenital malalignment of the great toenails, also known as congenital malalignment syndrome, is a dystrophic nail disorder caused by the lateral rotation of the nail matrix.

The malalignment results in alterations of the normal linear growth of the nail plate along the major axis of the distal phalanx.

Malalignment of the great toenail with lateral orientation of the long axis of the nail plate 

Congenital malalignment of the great toe nail in a toddler 

Congenital malalignment of the great toenail with onycholysis and subungal Pseudomonas infection causing a green nail 

Who gets congenital malalignment of the great toenails?

Congenital malalignment of the great toenails usually present at birth or in infancy. In some cases, it may not be identified until patients are older, as repetitive mechanical trauma to the nail unit over time can exacerbate subtle deviations in normal growth.

While the incidence of congenital malalignment of the great toenail is unknown, it is estimated to be observed in approximately 1–2% of children. As this condition is often misdiagnosed, higher incidence rates are suspected, and a high index of suspicion is required to diagnose chronic exacerbations of mild disease. A slight female predominance has been described.

What causes congenital malalignment of the great toenails?

The exact cause is not completely known. Associations include:

Genetics

• Observed to be inherited in an autosomal dominant fashion as seen in several generations of a single family, occurrence in monozygotic and dizygotic twins, and the degree of individual variability within the population.

Extrinsic factors

• Increased lateral tension of the extensor tendon of the hallux on the lateral portion of the proximal matrix, causing lateral rotation of the nail matrix
• Constriction of toes by amniotic bands
• Increased intrauterine pressure
• Vascular abnormalities during fetal life.

Mechanical stress

• Wearing tight shoes
• Activities such as dancing, soccer, and martial arts.

What are the clinical features of congenital malalignment of the great toenails?

Clinical features include:

• Lateral deviation of the nail plate, or (rarely) medial deviation
• Usually bilateral but unilateral cases have been reported
• Onychogryphosis (nail plate thickening)
• Chronic paronychia
• Nail discoloration (eg, brown, black, green-brown, or yellow)
• Transverse grooves across the nail (‘oyster shell’ appearance)
• Beau’s lines
• Frequently only involves the great toes, but other nails can be involved.

How do clinical features vary in differing types of skin?

Further research is needed to describe features of congenital malalignment of the great toenails in darker Fitzpatrick skin types and ethnicities.

What are the complications of congenital malalignment of the great toenails?

The complications of congenital malalignment of the great toenails may include:

• Onychocryptosis (ingrown toenail)
• Secondary infection eg, tinea unguium, acute or chronic paronychia
• Onychogryphosis
• Onycholysis, especially in adults
• Onychomadesis
• Subungual hyperkeratosis (scaling under the hyponychium)
• Acquired brachyonychia
• Nail discolouration
• Inability to cut the affected nail/s.

How is congenital malalignment of the great toenails diagnosed?

Congenital malalignment of the great toenails is diagnosed clinically based on its characteristic appearance.

Fungal cultures from nail scrapings may be performed to exclude tinea unguium or secondary infection.

There is no established role for nail biopsy, but it may be useful to exclude other diagnoses, for example if a tumour of the nail unit is suspected.

An X‐ray of the toes can further help to determine the degree of malalignment.

What is the differential diagnosis for congenital malalignment of the great toenails?

Table 1: Differential diagnoses for congenital malalignment of the great toenail by aetiology

What is the treatment for congenital malalignment of the great toenails?

Treatment can be either conservative or operative depending on the cause and degree of deviation.

Conservative treatment

Conservative treatment is appropriate for minimal deviation and involves:

• Wearing proper-fitted, comfortable footwear
• Podiatry review for burring of the thickened nail
• Regularly maintaining shorter nail length
• Toe taping, to counter the lateral pull exerted by the extensor tendons of the hallux and ameliorate distal nail wall hypertrophy
• Splinting/strapping.

Operative treatment

Operative treatment may be appropriate for severe deviations and involves:

• Rotation of the whole nail unit
• Positional correction or elongation of the extensor tendon of the hallux
• Nail matricectomy, either chemical or surgical
• Ungueodermal flap repair.

How do you prevent congenital malalignment of the great toenails?

To prevent complications, wearing proper footwear to prevent excessive nail pressure on the nail bed and avoiding repetitive traumatic injury in sports such as soccer, dancing, and long-distance running can be helpful.

What is the outcome of congenital malalignment of the great toenails?

Spontaneous resolution occurs in around half of those younger than 10 years. In others, the malformation may persist into adulthood, and can gradually restrict daily activities over time. In the case of severe malalignment, earlier surgery (eg, before 2 years of age) is likely to achieve better results.

Nail pathologies are often difficult to treat due to the requirement of long-term patient adherence to therapies, and recurrent macro- or micro-trauma.