Speckled lentiginous nevus syndrome with median nerve paresis: A rare syndrome with a new association.

Speckled lentiginous nevus (SLN) represents a mosaic phenotype which consists of café au lait macule superimposed by melanocytic nevi. Recently, SLN syndrome has been characterized where ipsilateral neurological abnormalities have been reported in association with SLN with papular type of melanocytic nevi only. This case describes the presence of ipsilateral thenar muscle atrophy with median nerve paresis in nevus spilus which had melanocytic nevi of the macular type alone, thus delineating a new association in SLN syndrome, hitherto unreported.

INTRODUCTION

Speckled lentiginous nevus (SLN) consists of a café au lait macule superimposed by multiple dark brown or black dots which represent macular or papular melanocytic lesions. “Nevus spilus” is used as a synonym.[1] SLN can be associated with segmental neurofibromatosis type 7, phacomatosis pigmentovascularis, and phacomatosis pigmentokeratotica.[234] Recently, SLN syndrome has been recognized as a neurocutaneous phenotype of SLN occurring in association with ipsilateral neurological abnormalities such as hyperhidrosis, muscle weakness, and dysesthesia.[5] SLNS represents a mosaic phenotype resulting from post-zygotic loss of heterogeneity.

We describe a case of SLNS associated with ipsilateral atrophy of the thenar muscles and median nerve paresis.

CASE REPORT

A 23-year-old Indian girl presented with a large pigmented lesion on her left arm and hand since birth. She reported darkening of the hyperpigmented patch over the years with the development of darkly pigmented spots over it. She also complained of weakness of the grip of left hand for the past 3 years. There was no history of trauma. Her medical history was otherwise unremarkable.

Cutaneous examination revealed a large café au lait macule running along the antero-medial aspect of left arm extending down to involve the palmar and the dorsal surface of the hand [Figure 1]. This macule was superimposed by multiple dark brown macules of size 0.2-1 cm. There was mild atrophy of the thenar eminence of the left hand [Figure 2]. Motor examination revealed deficient opposition and thumb flexion with positive pen test. Sensory examination revealed sensory loss to touch, temperature, and pain over medial nerve distribution of hand. A complete neurological checkup did not reveal any additional findings.

Figure 1

Large speckled lentiginous nevus on arm

Figure 2

Median nerve paresis appreciated as atrophy of lateral half of hand with mild medial clawing

Nerve conduction studies showed involvement of the left median nerve (both motor and sensory) as non-recordable with normal left ulnar nerve and right median (both motor and sensory) nerve conduction. There was weakness in the left abductor pollicis brevis muscle on electromyography documentation. Magnetic resonance imaging (MRI) of the cervical spine was normal. Histopathological examination from one of the darker macule showed features consistent with nevus spilus [Figure 3].

Figure 3

[H & E, ×40] showing nests of nevus cells in the upper dermis

DISCUSSION

SLNS is a recently described syndrome with a male to female ratio of 4:3.[26] These are usually present at birth but may appear during first years of life. Café au lait macules can be topped by either brown or black macules or papules. Macular SLN is considered hallmark of phacomatoses spilorosea (phacomatoses pigmentovascularis type 3),[7] whereas papular SLN is typically present in phacomatosis pigmentokeratotica and SLNS.[6] Neurological abnormalities reported with SLNS include nerve palsies with thinning of nerve and spinal muscular atrophy with fasciculations.[89] SLN involving the right half of thorax and right arm was described in a 27-year-old man with hypertrophy of the underlying pectoralis muscle.[10] Vente et al. described a large, painful, paresthetic SLN in a 42-year-old man on the left side of his trunk along with ipsilateral pronounced hyperhidrosis.[6]

Our patient showed ipsilateral atrophy of the thenar muscles of the hand and median nerve paresis. The MRI findings were normal. Carpel tunnel syndrome was also ruled out on account of a negative Tinnel sign, negative Phalen sign, and lack of evidence for median nerve compression. Thus, it was concluded that the presence of SLN along with ipsilateral median nerve paresis and thenar muscle atrophy were part of the wide spectrum of the SLN syndrome. The case is unique as such an association with a macular SLN has hitherto not been described in the literature. Also a new association of median nerve paresis described in our case further extends the clinical spectrum of SLNS.