Carotenaemia

What causes carotenaemia?

Excessive intake of carrots, and/or other yellow and green vegetables and citrus fruits are the usual cause of carotenaemia (American spelling carotenemia). Carotene is the chief precursor of Vitamin A and is converted to this in the mucosal cells that line the small intestine. Pancreatic lipase enzymes, bile salts, fat, and thyroid hormone aid conversion and absorption. Thus carotenaemia is more likely in some diseases such as liver disease, hypothyroidism and diabetes mellitus where this is impaired. In rare cases, a genetic defect in carotene metabolism may also be a cause of carotenaemia, without requiring excessive intake of carotene.

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, particularly in areas where the horny layer is thickened such as the soles and palms. It 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. The presence of yellowing of the sclera usually means there is increased circulating bilirubin and is known as jaundice.

Carotenaemia

Palm of patient with carotenaemia compared with normal palm

Palm of patient with carotenaemia due to antiepileptic drug

On testing the blood, serum beta-carotene levels are usually elevated by 3-4 times the normal level. Vitamin A levels should remain normal but are sometimes slightly high. Liver function tests should remain normal.

What is the treatment?

Carotenaemia 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.