Specific types of rashes provide important clues to many systemic illnesses in pediatrics. One must become expert at inspecting, describing, and identifying rashes so appropriate treatment can be initiated. Some rashes can be suggestive of cancer; immunologic disorders; systemic infection; or even impending cardiovascular collapse and signal the need for rapid, intensive management to avoid significant morbidity and mortality.

Mottling of the skin is described as a lacy, reticular rash. Mottling is seen in many conditions including shock, however if the child is otherwise well-appearing, shock is unlikely to be the cause. Infants tend to develop mottling when they are cold or when they have been exposed for a long period of time. This is often seen when an infant has been undressed and waiting in an exam room for an extended period of time for the doctor. However, mottling of the skin should raise concern for shock if it is coupled with other physical exam signs such as lethargy, tachycardia, and hypotension. For example, mottling can be a sign of decreased perfusion as in the case of coarctation of the aorta, with accompanying unilateral cutaneous mottling of the arm.