Extramedullary hematopoiesis in the kidneys in infant siblings with myelofibrosis.

Extramedullary hematopoiesis (EMH) is known to occur in clinical settings associated with severe anemia. Because very young children with anemia can usually recruit the still large compartment of red marrow, EMH is more frequently seen in adults. We have observed two young girls, who were unable to produce sufficient blood products in their marrow and instead developed EMH, one with documented and rarely reported renal involvement. They are described below.