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The association of Charcot-Marie-Tooth (CMT) disease with renal dysfunction is uncommon but has long been recognized in several families. Recently, mutations in the INF2 gene, which encodes inverted formin-2, were identified in patients with focal segmental glomerulosclerosis and a dominant intermediate form of CMT (CMTDIE, OMIM #614455). We describe the pathologic lesions of nerve biopsies from 6 patients with INF2-related CMTDIE. There were 4 females and 2 males; ages were from 12 to 47 years; durations between neuropathy onset and biopsy were from 2 to 37 years. Clinical phenotypes were similar to those seen in other forms of CMT disease, but there was always an associated proteinuria (and later renal failure). Motor median nerve conduction velocities were in the range of intermediate CMT disease. Pathologic lesions suggested chronic demyelination and remyelination associated with progressive axonal loss. By electron microscopy, we observed unusual whorl-like proliferations of flattened Schwann cell cytoplasm and anomalies of unmyelinating Schwann cell cytoplasm with supernumerary elongated extensions similar to those described in CMT4C. We also observed abnormal accumulation of β-actin in the cytoplasm of Schwann cells. Our results suggest that these lesions reflect a global disorder of the actin cytoskeleton in Schwann cells and that CMTDIE is the first peripheral nerve disorder associated with a Schwann cell actinopathy.

BACKGROUND: The aim of this study was to correlate MRI features and molecular characteristics in anaplastic oligodendrogliomas (AOs). METHODS: The MRI characteristics of 50 AO patients enrolled in the French national network for high-grade oligodendroglial tumors were analyzed. The genomic profiles and IDH mutational statuses were assessed using high-resolution single-nucleotide polymorphism arrays and direct sequencing, respectively. The gene expression profiles of 25 1p/19q-codeleted AOs were studied on Affymetrix expression arrays. RESULTS: Most of the cases were frontal lobe contrast-enhanced tumors (52%), but the radiological presentations of these cases were heterogeneous, ranging from low-grade glioma-like aspects (26%) to glioblastoma-like aspects (22%). The 1p/19q codeletion (n = 39) was associated with locations in the frontal lobe (P = .001), with heterogeneous intratumoral signal intensities (P = .003) and with no or nonmeasurable contrast enhancements (P = .01). The IDH wild-type AOs (n = 7) more frequently displayed ringlike contrast enhancements (P = .03) and were more frequently located outside of the frontal lobe (P = .01). However, no specific imaging pattern could be identified for the 1p/19q-codeleted AO or the IDH-mutated AO. Within the 1p/19q-codeleted AO, the contrast enhancement was associated with larger tumor volumes (P = .001), chromosome 9p loss and CDKN2A loss (P = .006), genomic instability (P = .03), and angiogenesis-related gene expression (P < .001), particularly for vascular endothelial growth factor A and angiopoietin 2. CONCLUSION: In AOs, the 1p/19q codeletion and the IDH mutation are associated with preferential (but not with specific) imaging characteristics. Within 1p/19q-codeleted AO, imaging heterogeneity is related to additional molecular alterations, especially chromosome 9p loss, which is associated with contrast enhancement and larger tumor volume.

Besides the common distal symmetrical sensory-motor polyneuropathy (DSP) that is often associated with autonomic dysfunction, diabetic patients may develop multifocal sensory-motor deficits (MDN) secondary to roots, plexus and nerve trunk involvement. Nerve ischaemia has been suggested as a common mechanism for the different patterns of diabetic neuropathies, yet the important clinical differences that exist between DSP and MDN suggest concurrent factors. In order to learn more on the subject, we prospectively studied 22 consecutive diabetic patients with MDN, for which other causes of neuropathy were excluded by appropriate investigations, including biopsy of a recently affected sensory nerve. Three patients had a relapsing course, and the others an unremitting subacute-progressive course. Painful MDN progressed over 2-12 months. The neurological deficit predominated in distal lower limbs which were involved in all patients, unilaterally in seven, bilaterally in the others, with an asynchronous onset in most cases. In addition, a proximal deficit of the lower limbs was present on one side in seven patients, and on both sides in six. Thoracic radiculoneuropathy was present bilaterally in two patients, and unilaterally in one. The ulnar nerve was involved in one patient, and the radial nerve in two. The CSF protein ranged from 0.40 to 3.55 g/l; mean: 0.87 g/l. Electrophysiological testing showed severe, multifocal, axonal nerve lesions in all cases. Asymmetrical axonal lesions were found in all nerve specimens. The mean density of myelinated axons was reduced to 1340 +/- 1070 per mm(2) of endoneurial area versus 8370 +/- 706 myelinated fibres/mm(2) in controls. The mean density of unmyelinated fibres was reduced to 5095 +/- 6875 per mm(2) (extremes: 0-26 600). On teased fibre preparations, 34 +/- 31% of the fibres were at different stages of axonal degeneration (extremes 0-99%); 7 +/- 6% of the fibres showed segmental demyelination or remyelination. Necrotizing vasculitis of perineurial and endoneurial blood vessels were found in six patients. Endoneurial seepage of red cells was present in 11 specimens, and endoneurial haemorrhage in five. Ferric iron deposits that characterize previous bleeding were found in seven patients, including two who had no red cells in the endoneurium. Perivascular mononuclear cell infiltrates were present in the nerve specimens of 21 out of 22 patients, prominently in four patients. In comparison, nerve biopsy specimens of 30 patients with severe distal symmetrical diabetic polyneuropathy showed mild epineurial mononuclear cell infiltrate in one patient and endoneurial seepage of red cells in another. We conclude that MDN is related to pre-capillary blood vessel involvement in elderly diabetic patients with a secondary inflammatory response.

Peripheral neuropathy is a rare, yet treatable manifestation of sarcoidosis, a multisystem disorder characterized by the presence of non-caseating granulomas that are seldom found in nerve biopsy specimens. In order to learn more about the subject, we reviewed our clinical and pathological findings in a series of 11 patients (six men and five women aged 26-83 years) with symptomatic neuropathy associated with characteristic granulomas in nerve biopsy specimens. Only two patients were known to have sarcoidosis before the occurrence of the neuropathy. The neuropathy was focal or multifocal in six patients, including one with a multifocal neuropathy associated with conduction blocks, and one with a multifocal axonal motor deficit. Four patients had a distal symmetrical deficit and one patient had a Guillain-Barre-like syndrome with facial diplegia and respiratory failure. Serum angiotensin-converting enzyme concentration was elevated in only two patients. Epineurial granulomas and perineuritis were present in all nerve specimens. The inflammatory infiltrates invaded the endoneurium, following connective tissue septae and blood vessels, in five patients. Multinucleated giant cells were found in eight patients and necrotizing vasculitis in seven. Inflammatory lesions were associated with variable, asymmetrical involvement of nerve fascicles and axon loss. A muscle specimen was sampled during the same procedure in 10 patients. It showed inflammatory infiltrates and granulomas in nine patients and necrotizing vasculitis in two. Immunolabelling showed a mixed inflammatory infiltrate of T cells (predominantly CD4+ cells) and macrophages, in keeping with a delayed hypersensitivity reaction. In addition to nerve involvement, all patients had at least one other tissue or organ affected, including muscle in nine patients, lungs and/or intrathoracic lymph nodes in eight, skin in three, arthritis in two, and peripheral lymph nodes, stomach and eye in one patient each. Most patients improved on corticosteroids. Two patients remain free of symptoms after 7 years. Severe side-effects of long-term treatment with corticosteroids occurred in two patients, leading to death in one. This study illustrates the wide range of clinical manifestations of sarcoid neuropathy and the frequent association of granulomatous inflammatory infiltrates with necrotizing vasculitis and with silent or symptomatic involvement of other organs.

In order to learn more about the vulnerability of nerve fibres to ischemia, a quantitative study of nerve fibre abnormalities was performed on biopsy specimens of the superficial branch of the peroneal nerve from 26 patients with vasculitic neuropathy: 20 had necrotizing arteritis, 5 a lymphocytic, and 1 a leucocytoclastic vasculitis on nerve and/or muscle biopsy. The density of myelinated fibres ranged from 25 to 7880 per mm2 (n = 8470 +/- 706 (SD]. There was a marked inequality in the density of nerve fibres between the fascicles of individual nerves with a mean coefficient of variation of 41 +/- 37 (SD) % versus 7.4 +/- 3.0% in controls. Loss of myelinated fibres, which was greater for fibres larger than 7 microns in diameter, was more severe than that for unmyelinated axons. Regeneration, which was assessed by the number of clustered axons, decreased when the density of myelinated fibres decreased, suggesting that severe nerve ischaemia precludes axonal regeneration. Wallerian degeneration affected on average 58% (range 5-100%) and segmental demyelination, mainly of the secondary type, on average 1.94% (range 1-10%) of teased fibres. It was concluded that (1) myelinated fibres are more vulnerable to ischaemia than unmyelinated axons; (2) large myelinated fibres are affected before the smaller ones; (3) segmental demyelination is uncommon in this context; (4) severe nerve ischaemia precludes axonal regeneration.