The pathogenesis of Crow-Fukase (POEMS) syndrome is not well known, and in some cases, a definite diagnosis is difficult to establish. Nerve fibers have been studied in about 120 peripheral nerve biopsies (PNBs), and a mixture of axonal and demyelinating lesions were found in most of them. We report five new cases of Crow-Fukase (POEMS) syndrome with ultrastructural examination of their PNBs. In every case, there were features of axonal degeneration and primary demyelination. Interestingly, uncompacted myelin lamellae (UMLs) were present in every case at a percentage of 1-7. The association of UML and Crow-Fukase (POEMS) syndrome was described 20 years ago but was only reported in a few studies and found in 31 of 41 cases. In fact, this association is very significant because apart from Crow-Fukase (POEMS) syndrome, UMLs can only be found with such a frequency in rare cases of Charcot-Marie-Tooth disease type 1B. UML was also reported in acute and chronic inflammatory demyelinating polyneuropathies but at a much lower percentage. Moreover, in our five cases, UML was frequently associated with a decrease in the number of intra-axonal filaments, and this finding raises the problem of relationships between myelin formation and neurofilaments. So far, glomeruloid hemangiomas present in the dermis of some patients are considered as the only specific criteria of Crow-Fukase (POEMS) syndrome, but we think UML can also be regarded as highly suggestive of this entity on condition that a thorough ultrastructural examination of a PNB is performed.