Dahl's sign
Encyclopedia
Dahl's sign is a clinical sign
in which areas of hyperpigmentation
are seen on the skin of the lower thigh
s and elbow
s. It occurs in patients with longstanding severe chronic obstructive pulmonary disease
.
The sign occurs because patients with COPD tend to sit forwards with their arms resting on their thighs, leading to chronic erythema
of the skin at the points of contact. Over time, haemosiderin released from red blood cell
s trapped in the skin is released causing a brown discolouration of the skin.
Air trapping
in the lungs of COPD patients causes the diaphragm
to be pushed down and flattened, which reduces the effect of contraction of the diaphragm during inspiration
. Sitting forwards pushes the abdominal contents upwards, increasing the curvature of the diaphragm and improving its effectiveness.
Bilateral cubital tunnel syndrome
may also be found in patients with Dahl's sign.
Dahl's sign was described by K.V. Dahl in 1970.
Medical sign
A medical sign is an objective indication of some medical fact or characteristic that may be detected by a physician during a physical examination of a patient....
in which areas of hyperpigmentation
Hyperpigmentation
In dermatology, hyperpigmentation is the darkening of an area of skin or nails caused by increased melanin.-Causes:Hyperpigmentation may be caused by sun damage, inflammation, or other skin injuries, including those related to acne vulgaris...
are seen on the skin of the lower thigh
Thigh
In humans the thigh is the area between the pelvis and the knee. Anatomically, it is part of the lower limb.The single bone in the thigh is called the femur...
s and elbow
Elbow
The human elbow is the region surrounding the elbow-joint—the ginglymus or hinge joint in the middle of the arm. Three bones form the elbow joint: the humerus of the upper arm, and the paired radius and ulna of the forearm....
s. It occurs in patients with longstanding severe chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease , also known as chronic obstructive lung disease , chronic obstructive airway disease , chronic airflow limitation and chronic obstructive respiratory disease , is the co-occurrence of chronic bronchitis and emphysema, a pair of commonly co-existing diseases...
.
The sign occurs because patients with COPD tend to sit forwards with their arms resting on their thighs, leading to chronic erythema
Erythema
Erythema is redness of the skin, caused by hyperemia of the capillaries in the lower layers of the skin. It occurs with any skin injury, infection, or inflammation...
of the skin at the points of contact. Over time, haemosiderin released from red blood cell
Red blood cell
Red blood cells are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen to the body tissues via the blood flow through the circulatory system...
s trapped in the skin is released causing a brown discolouration of the skin.
Air trapping
Air trapping
Air trapping, also called gas trapping, is an abnormal retention of air in the lungs where it is difficult to exhale completely. It is observed in obstructive lung diseases such as asthma, bronchiolitis obliterans syndrome and chronic obstructive pulmonary diseases such as emphysema and...
in the lungs of COPD patients causes the diaphragm
Thoracic diaphragm
In the anatomy of mammals, the thoracic diaphragm, or simply the diaphragm , is a sheet of internal skeletal muscle that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity from the abdominal cavity and performs an important function in respiration...
to be pushed down and flattened, which reduces the effect of contraction of the diaphragm during inspiration
Inhalation
Inhalation is the movement of air from the external environment, through the air ways, and into the alveoli....
. Sitting forwards pushes the abdominal contents upwards, increasing the curvature of the diaphragm and improving its effectiveness.
Bilateral cubital tunnel syndrome
Ulnar nerve entrapment
Ulnar nerve entrapment is a condition where the ulnar nerve becomes trapped or pinched due to some physiological abnormalities. -Classification:...
may also be found in patients with Dahl's sign.
Dahl's sign was described by K.V. Dahl in 1970.