Late onset dHMN II caused by c.404C>G mutation in HSPB1 gene.

Distal hereditary motor neuropathy (dHMN) type II is genetically heterogeneous. We report three siblings of a German family with late onset distal motor neuropathy due to the c.404C>G mutation in heat-shock 27-kDa protein 1 gene (HSPB1/HSP27). A 36-year-old mutation carrier, daughter of one sibling, did not present any clinical or electrophysiological abnormalities. The index patient (oldest brother) developed weakness of the distal lower limbs and nocturnal muscle cramps at the age of 54. After 5 years this patient developed an l-DOPA-responsive hypokinetic rigid syndrome, establishing a diagnosis of Parkinson's disease. Although none of the three other mutation carriers displayed Parkinsonian signs, a pathogenic relationship with Parkinson's disease remains a possibility, based on the known molecular pathology of HSPB1. The rare pathogenic HSPB1 c.404C>G mutation may predispose for late-onset of dHMN type II.