A unique presentation of trichofolliculoma in amniotic band syndrome

INTRODUCTION

Trichofolliculoma is a rare benign adnexal lesion, currently classified as a hamartoma originating from the hair follicle. It was first described by Miescher in 1944 as an unusual follicular neoplasm.^[1] Trichofolliculoma has not been linked to any systemic or cutaneous complications. Clinically, trichofolliculoma presents as a solitary, skin-colored papule or nodule with a central umbilication, often featuring protruding fine hairs.

Amniotic band syndrome (ABS), by contrast, is a congenital malformation complex caused by the entanglement of fetal tissues, most often limbs or digits, by fibrous amniotic bands.

Here, we present a case of a trichofolliculoma on the scalp in a male with constriction band syndrome.

CASE REPORT

A 31-year-old male patient presented with the chief complaint of a single painful, slowly growing lesion over the scalp for 6 months, associated with mild itching and discharge. There is no history of trauma or any topical application. There were no systemic symptoms or history of similar complaints in the past or in the family.

On general examination, kyphoscoliosis, left arm constriction band, gibbus, pectus excavatum, and short neck were noted [Figure 1]. On cutaneous examination, the vertex of the scalp showed a well-defined solitary whitish nodule of size 0.5 × 0.5 cm with central umbilication and a wool-like tuft of hairs [Figure 2].

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Figure 1:

Left arm constriction band (red arrow).

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Figure 2:

Well-defined solitary whitish nodule of size 0.5 × 0.5 cm with central umbilication and a wool-like tuft of hairs.

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Trichoscopy revealed an “erupting volcano” pattern composed of a central dilated pore with tufted white hairs (troll doll-like hair) and surrounded by a few vessels in a radial arrangement [Figure 3a and b].

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Figure 3

(a): Trichoscopy showing a central dilated pore with tufted white hairs resembling a troll doll; (b): “Erupting volcano” pattern composed of a central dilated pore with tufted white hairs (Dermlite dl4 dermoscope polarised mode, 10x).

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On histopathological examination, the epidermis showed invagination into the dermis with irregular cystically dilated follicular infundibulum filled with keratin and hair shafts. The infundibular epithelium was hyperplastic with radiating strands at the base and sides. The intervening fibrous stroma showed inflammatory infiltrates [Figure 4].

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Figure 4:

Histopathological examination shows epidermal invagination into dermis with irregular cystically dilated follicular infundibulum filled with keratin material and hair shafts (red circle). (Hematoxylin & eosin, 40x).

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Computed tomography (CT) of the dorsolumbar spine showed kyphoscoliosis of the dorsal spine and block vertebrae D1-D7, along with crowding of ribs. CT of the cervical spine was normal.

An X-ray of the left arm showed a type 2 constriction ring [Figure 5].

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Figure 5:

X-ray of the left arm showing the constriction ring (red arrow).

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Other laboratory investigations are within normal limits.

DISCUSSION

Trichofolliculoma is an uncommon hamartoma that typically manifests as a single, tiny papule or nodule.^[2] It most commonly manifests in adulthood and shows a predilection for the facial region, particularly the nasal area. However, involvement of other anatomical sites – including the external auditory canal, vulva, lips, intranasal cavity, and genitalia – has been reported. It is thought to be caused by the premature differentiation of pluripotent skin cells into hair follicles, while the exact cause is unknown.^[3] A tuft of white hairs gives a distinctive morphological appearance to trichofolliculoma. However, this special clinical presentation only emerges in about 15% of patients, and the majority have no distinguishing features.^[4] Depending on the stage of maturity, histopathology might change. Few secondary vellus hair follicles that originate from a main follicle are seen in the early stages. A thicker main follicle and fewer secondary follicles are shown in later phases.

Constriction ring syndrome, also known as Streeter’s dysplasia or ABS, is a congenital condition that occurs when loose fibrous bands of ruptured amnion adhere to and entangle the normal developing structures of the fetus. The incidence ranges approximately from 1:1,200 to 1:15,000 live births. Dermatological manifestations of ABS are important yet often under-recognized components of the condition. They typically result from mechanical constriction, ischemia, or scarring due to the amniotic bands. Cutaneous findings may include constriction bands, pseudosyndactyly with webbing, localized lymphedema, aplasia cutis congenita, nail abnormalities, and fibrous appendages.

Trichofolliculoma in ABS is an exceptionally rare occurrence, and presumed reasons are developmental disruption, trauma-related follicular remodeling, and aberrant regenerative signaling during fetal development. The treatment of choice is complete surgical excision with histopathological confirmation to ensure accurate diagnosis and prevent recurrence, which is rare when fully removed.^[5]

Follow-up is generally not required unless there is concern for recurrence or histological ambiguity, as malignant transformation has not been reported.

CONCLUSION

The coexistence of trichofolliculoma with ABS has not been previously reported, highlighting the uniqueness of this presentation. Given the rarity of this association, detailed documentation through case reports and series is essential to enhance understanding of the pathogenesis and expand the recognized spectrum of cutaneous manifestations in ABS.