Differential diagnostics of multifocal motor neuropathy (MMN) has many difficulties associated with a number of factors: rare nature of disease, polymorphic clinical forms and a phenotypic picture similar to peripheral motor neuron diseases. Such diseases also include rare nosological forms: amyotrophic lateral sclerosis, hereditary myopathies and neuropathies; their general phenotypic picture has a form of progressive flaccid paralysis, age of the disease onset and the nature of its course. However, different pathogenesis of these diseases requires a differentiated approach to therapy. This article deals with differential diagnostics of multifocal motor neuropathy, gives examples of modern diagnostic criteria necessary for diagnosing multifocal motor neuropathy and analyzes a clinical case with an incorrect diagnosis of multifocal motor neuropathy.

Miller-Fisher syndrome (MFS) — is rare form Guillain-Barre syndrome (GBS). The patient with signs of severe hyperemesis of gravidarum demonstarates development of Miller-Fisher syndrome in the second trimester of pregnancy. The morbidity is about 5–10%. It is considerable, that one third of pregnant patients need respiratory support in the period of disease. The article describes pathogenic treatment of Miller-Fisher syndrome in the aspect of potential risk for fetum and pregnant women.