TO THE EDITOR,

A 10-month-old, otherwise healthy girl visited Hanawa Kosei Hospital, presenting with a nodule in the perianal area.  Her mother noticed it three weeks previously.  Physical examination revealed a well-circumscribed, solitary, smooth-surface, reddish protruded nodule located anterior to the anus (Fig. 1).  Her mother did not wish examination by biopsy.  She is now under observation, but currently without marked changes.

Infantile perianal pyramidal protrusion was first described by Kayashima et al. [1], which appears at birth or soon. To date, nearly 100 cases have been reported [2], and almost all of the reported patients are girl.  The diagnosis is usually made based on its characteristic clinical features, which are not only pyramidal, but also expressed as “peanut”, “hen’s crest”, “leaf like”, or “tongue tip”.  Also, parents often do not wish biopsy or surgical intervention. 

Infantile perianal pyramidal protrusion is classified into constitutional, functional, and lichen sclerosus-associated type.  Additionally, Verma and Wollina [3] reported a case of infantile perianal pyramidal protrusion with an adjacent hemangiomatous plaque, raising a possibility that infantile perianal pyramidal protrusion may be a part of incomplete PELVIS (perineal hemangioma, external genitalia malformations, lipomyelomeningocoele, vesicorenal abnormalities, imperforate anus, and skin tag) syndrome.  Histology reveals elongated epidermis, dermal edema and fibrosis, with dilated vessels and mild cellular infiltrates.  Lichen sclerosus-like changes can be seen in a subgroup.

Although the etiology of infantile perianal pyramidal protrusion is still unclear, an anatomic weakness in the perineum may be associated. Whether infantile perianal pyramidal protrusion resolves spontaneously or not is still controversial, which may depend on the above three types.  Constitutive type is suggested to remain unchanged for many years. Functional type is associated with dietary changes, diarrhea, and constipation, and can be much improved by dietary modification. Lichen sclerosus-type is expected to respond to topical corticosteroid therapy [4].  Our case is planned to be under long-term conservative follow-up.