Lymphangioleiomyomatosis is a very rare (although predominantly found in women of childbearing age, childhood cases have been reported), progressive lung disease characterized by misdifferentiated unusual muscle cells that invade lung tissue and blood and lymph vessels. Leiomyomatosis, resultant from LAM, form to create bundles growing into the lung walls, blood and lymph vessels, obstructing these pathways. Obstruction leads to symptomatology that includes shortness of breath, chest pain, and (in more advanced stages) coughing blood. Despite the fact that the unusual cells are not cancerous in nature, their growth is unregulated by the usual mechanism, and they eventually grow and cause hypoxemia.