Yes, a child can be a hypochondriac, but their clinical presentation is different from adults. The most common symptoms of hypochondriasis in children are recurrent stomach pain, headaches, nausea, and fatigue. Another difference between child and adult presentation of hypochodriasis is that children rarely worry that they may have a serious medical illness.
But the course of illness in children with somatic complaints seems to depend on the parents' reaction to the child symptoms, as it is the parents who usually interpret the symptoms and the parents who seek medical attention for their child.