PROMM - THE EXPANDING PHENOTYPE - A FAMILY WITH PROXIMAL MYOPATHY, MYOTONIA AND DEAFNESS

We describe a family with a proximal myopathy, subclinical EMG myotoni a, cataracts and deafness. Transmission through two generations and do wn the male line confirms autosomal dominant inheritance. There was no abnormal expansion of the CTG triplet repeat in the last exon of the dystrophia myotonica protein kinase (DMPK) gene associated with myoton ic dystrophy. Heteroduplex analysis of all but the promoter region of the DMPK gene has excluded point mutations in this gene as an underlyi ng cause for this myotonic disorder. The family was not sufficiently i nformative to exclude linkage to the sodium channel gene SCN4A or the chloride channel gene CLC1. This family clearly fulfils the recently e stablished diagnostic criteria for PROMM (proximal myotonic myopathy) and in addition shows consistent severe deafness as a hitherto undescr ibed feature of PROMM. We discuss the diagnostic criteria of PROMM in relation to this family and other recent papers, all of which would no w fulfil the aforementioned diagnostic criteria for PROMM. (C) 1998 El sevier Science B.V. All rights reserved.