Uncompacted Myelin Lamellae in Peripheral Nerve Biopsy

Abstract

Since 1979, the authors have studied 49 peripheral nerve biopsies presenting uncompacted myelin lamellae (UML). Based on the ultrastructural pattern of UML they propose a 3-category classification. The first category includes cases displaying regular UML, which was observed in 43 cases; it was more frequent in 9 cases with polyneuropathy organomegaly endocrinopathy m-protein skin changes (POEMS) syndrome as well as in 1 case of Charcot-Marie-Tooth 1B with a novel point mutation in the P0 gene. The second category consists of cases showing irregular UML, observed in 4 cases with IgM monoclonal gammopathy and anti-myelin-associated glycoprotein (MAG) activity. This group included 1 benign case and 3 B-cell malignant lymphomas. The third category is complex UML, which was present in 2 unrelated patients with an Arg 98 His missense mutation in the P0 protein gene. Irregular and complex UML are respectively related to MAG and P0, which play a crucial role in myelin lamellae compaction and adhesion.

Weaning from the ventilator using bipap in myasthenia gravis

“…We have recently reviewed 49 cases of peripheral neuropathy with UML observed in a series of 1821 peripheral nerve biopsies studied since 1979. 5 We found typical UML in 1% or more of the myelinated fibers in 10 adult cases. There were 9 cases of POEMS syndrome and 1 case of Charcot-Marie-Tooth (CMT) 1B syndrome due to a codon stop mutation on the myelin protein zero gene.…”

“…5 UML must be differentiated from widened myelin lamellae, which are observed in patients with an immunoglobulin M (IgM) monoclonal gammopathy and serum anti-MAG (myelin-associated glycoprotein) activity. 2,5 Up to now, typical UML cases have mainly been reported in POEMS syndrome affecting Japanese and French patients, 2 but this myelin modification can be identified easily upon ultrastructural examination of nerve fragments. In addition, "macrophage-associated" demyelination, characteristic of CIDP, 2 is not seen in POEMS syndrome.…”

Neonatal Hyperoxia Exposure Disrupts Axon–Oligodendrocyte Integrity in the Subcortical White Matter

“…These abnormalities in myelin compaction may be attributed to altered PLP (Bakhti et al, 2013) or MAG protein levels. Interestingly, myelin compaction defects were found to be related to changes in MAG and P0 disorders of the PNS (Vital et al, 2003). One possible mechanism that could contribute to these changes in myelin protein expression and incomplete oligodendroglia maturation is altered glutamate homeostasis, which is acutely disrupted after hyperoxia (Schmitz et al, 2011).…”

Recommendations on diagnostic strategies for chronic inflammatory demyelinating polyradiculoneuropathy

“…A monoclonal IgG or light chain (especially lambda) may indicate the presence of a POEMS (polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy and skin changes) syndrome 54 55. CSF examination is highly recommended to look for abnormal cells.…”