PROXIMAL MYOTONIC MYOPATHY (PROMM) - CLIN ICAL VARIABILITY WITHIN A FAMILY

Proximal myotonic myopathy (PROMM) is a newly described autosomal domi nant inherited disorder characterized by predominant proximal weakness of the legs, mild clinical myotonia or myotonia on electromyograms (E MG), cataracts and slight elevation of liver enzymes,The trinucleotide (cytosine,thymine,and guanine) repeat size of the myotonic dystrophy (DM) gene is normal. Magnetic resonance imaging of the brain may revea l a peculiar pattern of white matter abnormalities. We describe seven patients in a new family with PROMM. The only symptoms may be subclini cal myotonic changes in the EMG or cataracts, but symptoms may also in clude severe proximal weakness of the legs and painful paraesthesia. P ROMM is an important differential diagnosis of myotonic dystrophy; and because of the proximal weakness it is also a differential diagnosis of other muscle diseases such as limb girdle dystrophy, metabolic and endocrine myopathies, and myositis. Because of the variability of the symptoms, for the definite diagnosis of PROMM it may require the exami nation of other family members.