Which Is INCORRECT Regarding Myasthenia Gravis

Which is INCORRECT regarding myasthenia gravis?

A) Onset in females usually 2nd and 3rd decades, males 7th and 8th decades.
B) The thymus is abnormal in 75% and removal will improve symptoms in the majority.
C) Acute crises in these patients can be due to myasthenia crisis or cholinergic crisis secondary to the medication.
D) Muscle weakness is more marked peripherally.
E) Diagnosis with Ach receptor antibody testing is possible but false negatives occur in 15%.