The studies reported in this thesis aimed to survey the prevalence of inclusion body myositis (IBM), to describe its clinical features and course, to investigate whether the major... Show moreThe studies reported in this thesis aimed to survey the prevalence of inclusion body myositis (IBM), to describe its clinical features and course, to investigate whether the major histocompatibility complex predisposed subjects to IBM and autoimmune disorders (AID), to investigate the possible affliction of the neuromuscular junction (NMJ) and finally, to study whether the progression of IBM could be slowed down. On July 1st, 1999, the prevalence was estimated on at least 4.9.10-6 inhabitants in the Netherlands. The incidence rate increased since the 1980s. Time of onset was generally after the age of forty. Symptons at onset could be linked to weakness of the quadriceps muscles , the finger flexors or pharynbgeal muscles. Weakness showed a variable progression rate. Progression of weakness was faster when onset was over the age of 56. Ankylosis was common, but could be helpful in performing skilful movements. Ventral muscles were more frequently and severely affected than dorsal muscles, and girdle muscles were relatively spared, a specific pattern. Repetitive nerve stimulation studies showed normal compound muscle action potential patterns suggestive of normal NMJ transmission. In IBM patients a high frequency of AID was observed. Compared to controls, patients had a high frequency of HLA-antigens of the HLA-A1-B8-DR3-DR52-DQ2 complex. This high frequency could be related to IBM alone and not to the presence of AID. Lastly, in a randomized placebo controlled trial with methotrexate no important effect on weakness progression could be demonstrated. Show less
