What is this congenital perineal lesion called?

This is a perineal groove.

This rare but benign malformation of the perineum is characterized by a superficial skin defect that creates a moist groove corresponding to a non-epithelialized mucosa, extending from the posterior part of the posterior fourchette to the anus.

This malformation is usually isolated and, in the absence of any clinically evident genital or anal anomaly, requires no investigation.

The lesion is usually asymptomatic and tends to disappear spontaneously after the age of two. This condition is important for pediatricians and dermatologists to be aware of, as it can pose differential diagnostic problems, especially if the congenital nature of the condition is unknown.

• Sexual abuse must be systematically considered in the presence of a perineal lesion in a child with no obvious clinical diagnosis, regardless of age or family context.
   
• Erosive lichen sclerosus is not compatible with this presentation, nor is any vesiculobullous inflammatory dermatosis, due to the unique, painless and fixed nature of the lesion.
   
• Infantile perianal pyramidal protrusion is a benign skin lesion that occurs most frequently in girls under 5 years of age, possibly reflecting an anatomical weakness of the perineum. It is an asymptomatic, soft, smooth, pink or flesh-colored skin protrusion with the same topography as the perineal groove.