A dust storm, also called a sandstorm, is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front or other strong wind blows loose sand and dirt from a dry surface. Fine particles are transported by saltation and suspension, a process that moves soil from one place and deposits it in another. The arid regions of North Africa, the Arabian peninsula, Central Asia and China are the main terrestrial sources of airborne dust. It has been argued that poor management of Earths drylands, such as neglecting the fallow system, are increasing the size and frequency of dust storms from desert margins and changing both the local and global climate, as well as impacting local economies.The term sandstorm is used most often in the context of desert dust storms, especially in the Sahara Desert, or places where sand is a more prevalent soil type than dirt or rock, when, in addition to fine particles obscuring visibility, a considerable amount of larger sand particles are blown closer to the surface. The term dust storm is more likely to be used when finer particles are blown long distances, especially when the dust storm affects urban areas. Causes
As the force of dust passing over loosely held particles increases, particles of sand first start to vibrate, then to move across the surface in a process called saltation. As they repeatedly strike the ground, they loosen and break off smaller particles of dust which then begin to travel in suspension.
Therefore, in patients with COPD and significant degrees of clubbing, a search for signs of bronchogenic carcinoma (or other causes of clubbing) might still be indicated. A congenital form has also been recognized. Hypertrophic pulmonary osteoarthropathy
A special form of clubbing is hypertrophic pulmonary osteoarthropathy (HPOA), known in continental Europe as Pierre Marie-Bamberger syndrome. This is the combination of clubbing and thickening of periosteum (connective tissue lining of the bones) and synovium (lining of joints), and is often initially diagnosed as arthritis. It is commonly associated with lung cancer. Primary hypertrophic osteoarthropathy
Primary hypertrophic osteoarthropathy is HPOA without signs of pulmonary disease. This form has a hereditary component, although subtle cardiac abnormalities can occasionally be found. It is known eponymously as the Touraine–Solente–Golé syndrome. This condition has been linked to mutations in the gene on the fourth chromosome (4q33-q34) coding for the enzyme 15-hydroxyprostaglandin dehydrogenase (HPGD); this leads to decreased breakdown of prostaglandin E2 and elevated levels of this substance. Pathogenesis
The exact cause for sporadic clubbing is unknown. Theories as to its cause include:

Vasodilation (i.e., distended blood vessels). Secretion of growth factors (e.g., platelet-derived growth factor and hepatocyte growth factor) from the lungs. Overproduction of prostaglandin E2 by other tissues. Increased entry of megakaryocytes into the systemic circulation. Under normal circumstances in healthy individuals, megakaryocytes that arise from the bone marrow are trapped in the pulmonary capillary bed and broken down before they enter the systemic circulation.