Does Hereditary Neuropathy with Liability to Pressure Palsy Predispose to Schwannomatosis?

Hereditary neuropathy with liability to pressure palsy (HNPP) is an autosomal dominant demyelinating peripheral neuropa-thy. The classical clinical presentation consists of recurrent, transitory, and painless focal neuropathies, mostly at sites of peripheral nerve entrapment and often triggered by minor nerve trauma. 1 Anatomopathological examinations reveal seg-mental demyelination and remyelination with focally thickened myelin sheaths called tomacula1. HNPP is probably un-derdiagnosed, and reportedly 10–15% of mutation carriers remain clinically asymptomatic. 2 Schwannomas, which are the most common benign peripheral nerve tumors in adults, are highly homogeneous tumors that are composed of Schwann cells and usually occur singly in otherwise normal individuals. Multiple schwannomas in the same individual suggest the existence of rare genetic diseases , such as neurofibromatosis type 2 (NF2), which is characterized by bilateral vestibular schwannomas. The occurrence of multiple nonvestibular schwannomas has been distinguished as schwannomatosis since it is a clinical entity distinct from other forms of neurofibromatosis. 3 Hereditary neuropathy with liability to pressure palsy was diagnosed in one patient at the age of 48 years, and in his two sons, at the age of 8 and 16 years. Molecular genetic analysis revealed the usual 1.5-megabase deletion of the gene encoding peripheral myelin protein 22 (PMP22) on chromosome 17p11.2-12 in these three patients. The patient's father suffered from a sensory-predominant neuropathy, but he did not carry deletion of PMP22. His mother suffered from transitional numbness and palsy, but did not undergo PMP22 analysis. At the age of 52 years this patient presented with a voluminous and painful schwannoma of the left median nerve at the forearm, which required surgery; 2 years later lumbar magnetic resonance imaging (MRI) was performed due to chronic distal numbness in his lower limbs and intermittent pain in his left foot. A homogeneous, well-demarcated, and contrast-enhanced intradural ovoid mass (6×3×4.5 mm) was found localized to the left side, in front of the L3–L4 disc (Fig. 1). This mass was suggestive of a new schwannoma. The same patient presented 6 months later with a painful tumefaction at the lateral side of his right thumb. This tumor was removed and histopathological examination diagnosed a new schwan-noma. Brain MRI revealed neither vestibular schwannomas nor meningiomas. Ophthalmological and dermatological examination yielded normal findings. To the best of our knowledge, two other cases of genetically diagnosed HNPP combined with schwannomas have been reported. This third case strongly suggests that this association is not fortuitous. An association between schwannomas …