What is carotenaemia?
Carotenaemia (American spelling carotenemia) is the term used for excessive carotenoids in the blood. Strictly speaking, excessive carotene in the skin should be called carotenoderma. The terms xanthoderma (yellow skin) and carotenosis are also used. Carotenaemia is usually harmless.
What are carotenoids?
Carotenoids are yellow coloured, lipid-soluble compounds found in red, orange, yellow and green vegetables and fruit. They include:
- alpha- and beta carotene
- lycopene (red colour in tomatoes)
Carotenoids are a normal part of our diet and contribute to the normal colour of our skin. They also help protect our skin from sunburn.
Carotenoids are precursors of an essential vitamin, Vitamin A or retinol. Conversion takes place in the mucosal cells that line the small intestine and in the liver. Pancreatic lipase enzymes, bile salts, fat, and thyroid hormone aid conversion of carotenoids to vitamin A. Carotenoids are cleared from the body in sweat, sebum, urine and faeces.
Although mostly safe, excessive ingestion of the carotenoid canthaxanthin has been associated with yellow deposits on the retina, visual defects and other adverse effects.
What causes carotenaemia?
Carotenaemia is usually due to excessive intake of carrots, pumpkin and/or other yellow and green vegetables and citrus fruits. It can also be due to taking nutritional supplements. This is called primary carotenaemia and appears several weeks after increased ingestion of the responsible foods.
Carotenaemia with normal intake of carotenoids can however be a sign of underlying illness. This is secondary carotenaemia. Examples include:
- increased blood fats (hyperlipidaemia), which bind the carotenoids preventing their excretion
- liver disease, hypothyroidism and diabetes mellitus, which impair the conversion of carotenoids to retinol.
- nephrotic syndrome, which prevents excretion of carotenoids in the urine
In rare cases, a genetic defect in carotene metabolism may also result in carotenaemia, even when the intake of carotene is normal.
Who gets carotenaemia?
Carotenaemia can occur at any age but is most common in young children fed large amounts of commercial infant food preparations. These foods often contain carrots, pumpkin, squash, spinach and sweet potato, all of which are high in carotene. Cooking, mashing and pureeing these foods make carotene more available for absorption. Carotenaemia has also been found in vegetarians or food faddists who over-indulge in carrots and oranges.
What are the clinical features?
Carotenaemia is characterised by yellow discolouration of the skin (carotenoderma, xanthoderma), particularly in areas where the horny layer is thickened such as the soles and palms. The yellow colour is also most evident on areas where subcutaneous fat is abundant.
The sclera (white outer coating of the eyeball) and mucous membranes (eyes, mouth, nostrils etc) are unaffected by carotenaemia – the presence of yellow sclera usually means there is increased circulating bilirubin and is known as jaundice.
Serum beta-carotene levels are usually elevated by 3-4 times the normal level in a patient with visible carotenaemia. Vitamin A levels should remain normal but are sometimes slightly high. Liver function tests should remain normal in primary carotenaemia.
What is the treatment of carotenaemia?
The skin colour can return to normal with dietary modification. Patients should be advised what foods contain carotene and advised not to overeat these foods. Even though serum levels of carotene may return back to normal soon after restricting carotene intake, the yellow colour of the skin may persist for a few months due to accumulated carotene in tissues.
Beta-carotene is an antioxidant and is sometimes used to treat photosensitivity disorders such as polymorphous light eruption and erythropoeitic protoporphyria. However its use has not been supported by controlled clinical trials, nor has it been found to reduce the risk of sunburn or to prevent skin cancer.