Mottling is the appearance of patchy, discolored skin in a net-like or lacy pattern, often referred to medically as livedo reticularis. This distinctive skin change is strongly associated with the physiological processes that occur at the end of life, which often leads to immediate concern for impending death. While mottling does signal a serious decline in circulation when it appears in a gravely ill person, it is important to understand that it is not exclusively a sign of mortality.
The Appearance and Mechanism of Mottling
Mottling presents as a marbled or net-like pattern of discoloration across the skin. This pattern is typically reddish-blue, purple, or sometimes dark brown on deeper skin tones, and it is caused by disturbances in the small blood vessels just beneath the skin’s surface.
The lace-like appearance is a direct result of uneven blood flow, where some small arteries supplying the skin constrict while the surrounding tiny veins and venules dilate. This process of vasoconstriction significantly slows blood flow to the skin.
As the blood moves sluggishly through the dilated surrounding capillaries and venules, it gives up its oxygen, becoming deoxygenated. The pooling of this oxygen-depleted blood creates the distinct purplish or bluish discoloration visible through the skin, forming the characteristic web-like pattern.
Temporary Causes and Reversible Mottling
In many situations, mottling is a temporary and harmless physiological response, particularly to environmental changes. Exposure to cold temperatures is the most common cause, triggering a reflex known as physiologic livedo reticularis or cutis marmorata.
The body conserves heat by temporarily constricting peripheral blood vessels in the skin, which diverts blood away from the surface. This cold-induced mottling is especially common in infants and young children, but it can affect adults as well.
Once the skin is warmed, the blood vessels relax, and the mottling resolves quickly. Certain medications, such as amantadine or interferon, can also cause temporary or persistent mottling as a side effect due to their effect on blood flow. Additionally, mild emotional stress can lead to the release of hormones that temporarily affect circulation, resulting in a transient mottled appearance.
When Mottling Signals Critical Decline
Mottling becomes a sign of severe systemic failure when it occurs in the context of a life-threatening illness or injury. In these critical situations, the body is actively shunting blood away from non-essential organs, like the skin, to maintain perfusion of the heart, brain, and kidneys.
This redirection of blood flow is a desperate attempt by the body to survive a severe drop in blood pressure or poor cardiac output. Conditions such as septic shock, severe hypovolemic shock from blood loss, or cardiogenic shock from heart failure all cause this profound circulatory collapse.
When associated with end-of-life processes, mottling reflects the body’s natural shutdown and is often seen in the final hours or days. The discoloration typically begins in the extremities, such as the feet, knees, and hands, and then progressively spreads toward the torso as circulation continues to fail.
Associated Symptoms and Emergency Action
If mottling appears suddenly and does not resolve with warming, especially if accompanied by other systemic symptoms, it may indicate a medical emergency. Signs of a dangerous drop in tissue perfusion include changes in mental status, such as confusion, drowsiness, or unresponsiveness.
Low blood pressure, a rapid or irregular heart rate, and difficulty breathing are also serious warning signs that should prompt immediate attention. If mottling is generalized and is seen alongside clammy, pale skin, a person should be treated for shock.
In these instances, the immediate action is to call emergency medical services. For persistent mottling without these accompanying danger signs, consulting a physician for a full evaluation to rule out underlying autoimmune or vascular conditions is the appropriate next step.