Few reports in the literature describe isolated peripheral neuropathies in relation to Mycoplasma pneumoniae infection without concurrent damage to the central nervous system. To our knowledge only a single case of mononeuritis multiplex with brachial plexus neuropathy coincident with M. pneumoniae has been documented until now. Here we present the first clinical case of lobar M. pneumoniae pneumonia in a 19-year-old female patient, where coincident neurological complications manifested as unilateral brachial plexus neuropathy, affecting axillar and suprascapular nerves. Isolated M. pneumoniae from sputum belonged to P1 type 2 and to MLVA type 3-6-6-2. No mutation associated with macrolide resistance in domain V of the 23S rRNA gene was detected. Serological testing of a GM1 antibody showed positive results, which might support the role of immunologic mechanisms in the pathogenesis of peripheral neuropathies related to M. pneumoniae infection.