Giant congenital melanocytic nevus with developmental dysplasia of bilateral hip: a rare association.

Giant congenital melanocytic nevi are rare congenital disfiguring benign neoplasms with a risk of transformation to malignant melanoma. They often present with various extra-cutaneous features. Here, we describe a case of giant melanocytic nevus with developmental dysplasia of bilateral hip, a novel association.

What was known?

The documented associations of giant congenital melanocytic nevus are neurocutaneous melanocytosis, spina bifida occulta, meningocoele, club foot, neurofibromatosis, lipomatosis, and hypertrophy and atrophy of limbs.

Introduction

Congenital melanocytic nevi (CMN) are defined as melanocytic nevi present at birth or shortly thereafter. The widely accepted classification divides CMN into small (<1.5 cm), medium (1.5-19.9 cm) and large or giant (>20 cm) nevi, based on the maximum diameter expected to be reached by adulthood.[1] Considering the expected growth rate, CMN measuring at least 6 cm on the trunk and 9 cm on the head in a neonate are labeled as giant congenital melanocytic nevi (GCMN).[2] GCMN are usually confined to the skin, but rarely invade the underlying fascia, muscle, or further deep structures. The estimated life-time risk for malignancy h (cutaneous and noncutaneous), is 4.5-10%.[3] GCMN have been described to be associated with spina bifida occulta, neurofibromatosis, lipomatosis, and various other disorders. Our case highlights a new association of giant CMN with developmental dysplasia of bilateral hip with significant asymmetry of both sides’ limb girths at the level of thighs, adding further to the aesthetic and psychological sequelae of GCMN.

Case Report

A 7-month-old male child presented to us with a large, pigmented flat lesion of irregular shape and colour, covering almost 70% of the trunk. The lesion was present since birth and has been following a proportional growth with the growth of the child. The mother also gave a history of noticing asymmetry of girth of the thighs since birth. The child has been otherwise healthy and there was no history of trauma or any neurological symptoms. He was delivered through a full term normal vaginal delivery without any obstetric complications. His physical, mental, and social milestones were appropriately achieved without any signs of developmental delay till the present date. The mother denied noticing any changes suggestive of malignant transformation like sudden accelerated growth, ulceration, bleeding, and induration in the nevus. There was no family history of similar presentations.

On cutaneous examination, the child had a large, irregular, well-defined, unevenly pigmented, flat melanocytic nevus with diffuse bluish-brown to black color, encircling the entire trunk. The maximum diameter was measured to be 33 cm, extending from the upper back to the left thigh, posteriorly. It had a smooth surface, with localized hypertrichosis over the left thigh. There were a total of 20 satellite lesions distributed over the arms, forearms, upper trunk, thighs, and legs, beyond the border of the main nevi. The child also had a swelling, measuring about 6 cm in diameter, on the lateral side of left lumbar area covered by the GCMN [Figure 1].

Figure 1

(a) Anterior view: Giant congenital melanocytic nevi (GCMN) covering left side of the chest, entire abdomen, bilateral groins, and left thigh with significant asymmetry of thighs. (b) Posterior view: GCMN spread over back, buttocks, left thigh. (c) An ill-defined lipoma, measuring about 6 cm in diameter, on the lateral side of the left lumbar area, covered by the GCMN

The swelling was well defined, soft and non-tender, mobile, without any surface changes. Systemic examination was unremarkable. Palpation of spines revealed no abnormalities. The child had asymmetry of thighs’ girth, with the mid-thigh circumference of the right thigh measuring 4 cm more in contrast with the left thigh. Systemic examination was unremarkable. Mucosa, hair, nail, palms, and soles were normal. Ophthalmologic and neurological examinations revealed no abnormalities. On investigation, complete hemogram, biochemical parameters, and urine complete examination were all within normal limits. X-ray of hip showed developmental dysplasia of bilateral hip. Ultrasound examination of both hips demonstrated non-ossified femoral cartilage [Figure 2].

Figure 2

(a) X-ray antero-posterior view showing bilaterally dislocated hips. (b) X-ray Von Rosen view showing bilaterally dislocated hips

Brain and spinal magnetic resonance imaging was performed to detect neurocutaneous melanocytosis, which revealed a normal study. An excision biopsy from the nevus showed nests of rounded melanocytes in the papillary dermis extending deep into the reticular dermis confirming the diagnosis of CMN. Biopsy was performed from the mass over the left lumbar area, which revealed mature adipocytes, suggestive of lipoma [Figure 3].

Figure 3

(a) H and E staining (×40): Higher magnification showing rounded melanocytes arranged in clusters in papillary and reticular dermis. (b) H and E staining (×10): Melanocytes arranged in clusters or nests in upper, middle, and lower dermis. (c) H and E staining (×40): Histopathology of the mass on left lumbar area showing collection of mature adipocytes, confirming the diagnosis of lipoma

Discussion

CMN differs from acquired melanocytic nevus by its presence at birth, tendency for larger size and a greater malignant potential.[4] CMN are caused by malformations of the neuroectoderm and occasionally neural elements, following de-regulated growth and arrest of melanocytes during migration from the neural crest to the skin.[5] The surface of the nevus may be smooth, rugose, and nodular with terminal hairs, which become more prominent as the infant grows. They are mostly found on trunk, followed by the limbs and the head. The nevus grows proportionately with the growth of the child. Multiple smaller congenital nevi called satellite lesions may also be seen in the vicinity of the main nevus. The importance of CMN lies in the fact that these lesions may be precursors of malignant melanoma. The chances of melanoma arising in GCMN are more with large size, i.e., CMN >40 cm in diameter, truncal locations, and >50 satellite nevi.[67] Various associated abnormalities have been reported with giant CMN. The documented associations are with neurocutaneous melanocytosis, spina bifida occulta, meningocoele, club foot, neurofibromatosis, lipomatosis, and hypertrophy and atrophy of limbs.[8] There have been few reports of epidermal nevus syndrome, Carney complex, premature aging syndromes, and ambiguous genitalia association with GCMN.[910] Histologically, GCMN can have deeper structure involvement of the skin with nests not only at the epidermal–dermal junction, but often within deeper tissues, including the reticular dermis, subcutaneous fat, muscle, fascia, neurovascular structures and appendage involvement. These associations may probably be due to a defect in neural crest, which is the origin not only of melanoblasts but also of Schwann cells, sensory ganglia, bone, fat, muscles, and blood vessels.[111213] It has been suggested that a defect in the neural crest may lead to abnormal development of any of its derivatives.[12] Though theoretically GCMN runs a risk of bony structures or joint involvement, but existing literature lacks evidence to support this hypothesis. This case of GCMN highlights this association in a 7-month-old male child who presented with bilateral developmental dysplasia of hip joints with significant asymmetry of limbs.

What is new?

The novel association of giant congenital melanocytic nevus with developmental dysplasia of bilateral hip.