As a pediatric hand therapist, I see clients who hold their pens and pencils a little bit differently than most. Typically, these clients are using a different grip to compensate for weakness or loose joints. An altered grasp is not in itself a bad thing until it creates a problem.
The problem is usually a complaint of pain with handwriting. An individual with loose joints develops an altered grasp pattern in order to increase stability when writing, thus allowing them to write clearly. An example of a modified grip is excessive extension of the tip of the fingers or thumb along with excessive flexion of the second joint of the thumb.
Another example involves holding the pencil tight in the first web space while using all four fingers and thumb to stabilize the pencil.