We report a case of eruptive plexiform schwannomas in a child with newly diagnosed Neurofibromatosis II. After the initial eruption of lesions, there was no subsequent development of any cutaneous lesions to our knowledge.
A nine-year-old male with a past medical history significant for a cataract at age two, with no known family history of neurocutaneous disorders, presented with a stumbling gait and hip pain in May 2010. Orthopedic examination revealed no traumatic cause and a neurological evaluation was undertaken. Two months later, in July of 2010, an MRI of his spine revealed a thoracic spine tumor. Within weeks, paralysis ensued. Surgical resection of the tumor revealed a meningioma at the level of T5/T6. On further examination, bilateral acoustic neuromas were discovered despite the patient having no hearing deficits. A diagnosis of Neurofibromatosis II was rendered at this time.
Nearly three months later, in October of 2010, dermatology was called to evaluate multiple new asymptomatic brown lesions on his trunk and extremities. On physical examination, multiple papillated flesh- to brown-colored round to oval plaques were present on the trunk and extremities (Figures 1-2). A 3 mm punch biopsy was performed on an abdominal lesion to rule out neurofibroma versus a connective tissue nevus. Of note, these lesions became painful within two weeks.
Histopathology revealed a dermal neoplasm with plexiform architecture (Figures 3-4). The neoplasm consisted of well-circumscribed fascicles of spindle cells with thin wavy nuclei and pale pink cytoplasm consistent with neural origin. Immunohistochemical staining was consistent with a plexiform schwannoma (S100 positive diffusely, Neurofibromin patchy throughout, Epithelial Membrane Antigen positive, Smooth Muscle Antigen negative, Desmin negative). Given the clinical setting, these lesions were believed to be eruptive plexiform schwannomas, not previously reported to arise in this fashion.
Neurofibromatosis is an autosomal dominant neurocutaneous disorder. It is considered to be one of the phakomatoses, consisting of both cutaneous lesions and peripheral or central nervous system neoplasms.
Of the eight described subtypes of Neurofibromatosis, the first two are the most notable. Type I Neurofibromatosis (NF I) or peripheral neurofibromatosis, also known as von Recklinghausen, is the classical type in which we see café-au-lait macules, neurofibromas, axillary freckling, Lisch nodules, optic nerve gliomas, severe scoliosis, macrocephaly, and sphenoid wing dysplasia (occurs 1:3,000 births).
Type II Neurofibromatosis (NF II) or Bilateral Acoustic Neurofibromatosis (BAN) is much rarer (1:25,000 births). This disorder arises secondary to a mutation of the Merlin gene (chromosome 22 at position 12.2), disabling regulation of cell division and proliferation, and resulting in tumors affecting both of the auditory nerves. This is why the most common presenting symptom is hearing loss. These patients have multiple tumors on the cranial and spinal nerves, including meningiomas, gliomas, schwannomas with a paucity of cutaneous lesions such as café-au-lait macules or plaque type schwannomas, in contrast to Neurofibromatosis I.
A diagnosis of NF II can be made if one of the following criteria is present: