Diabetes

MELLITUS AND THE SKIN

Skin manifestations are not uncommon in patients with diabetes mellitus and can precede or appear during the course of the disease. Find out more about some of the common skin conditions by poring over this interesting report by Dr Colin Theng, Consultant Dermotologist, National Skin Centre

While some cutaneous (those relating to or affecting the skin) manifestation may be a result of acute metabolic derangements or chronic degenerative complications, other cutaneous changes may appear independent of these factors.

The skin manifestation of diabetes can be broadly divided in the following groups:
1.      infectious
2.      non-infectious
3.      skin manifestations as a result of diabetes treatment.
 

INFECTIOUS

Cutaneous infections occur more frequently in diabetic patients and between 20 and 50% of diabetic patients may have skin infections. This is often related to poor glycaemic control.

The increased susceptibility to infection may be due to a variety of reasons including impairment of the microcirculation, neuropathy and an altered immune response. These factors may similarly explain the poor wound healing often seen in patients with diabetes mellitus. Abnormal leukocyte (white blood cell) function has been demonstrated in hyperglycaemic individuals. Staphylococcus aureus infections are common and patients may present with furuncles (boils) or carbuncles (pus-filled bump). (fig 1)

Candida infections are also more commonly seen in diabetic patients. Sites of candida infection include the mouth, glands and vulva and flexural areas. In women, they may present with recurrent vulval thrush while their male counterparts may present with a candida balanitis.

Erythrasma is an infection that commonly affects the armpit or fold areas and appears as a well demarcated red-brown patch. This is due to infection with the corynebacterium minutissimum bacteria. It can be itchy and is often mistaken as a fungal infection.

Severe infections that occur more commonly in diabetic patients include malignant onus externa and necrotizing faciitis.

Malignant otitis externa is an infection of the external auditory canal. This infection is caused by pseudomonas aeruginosa in majority of the cases. Invasion of the base of skull can occur resulting in cranial nerve damage and meningitis. This condition is associated with a high mortality rate and is more commonly seen in immunocompromised patients. The elderly diabetic is more susceptible while this is rarely seen in children.

Necrotising faciitis is a rare but serious infection and occurs more commonly in diabetic patients. This infection may begin as a minor skin injury such as a boil or insect bite and can spread rapidly. The infection can cause systemic symptoms with extensive tissue necrosis or death. Unfortunately, this may result in limb amputation and can even lead to death. In diabetic patients, the index of suspicion should be high in patients with cellulitis (a spreading inflammation of subcutaneous or connective tissue), with signs of fever, tachycardia (rapid heart rate) and leukocytosis.

NON-INFECTIOUS

A number of skin conditions are seen more commonly in patients with diabetes mellitus.

These include the following:

1.    acanthosis
2.    nigricans
3.    necrobiosis lipoidica
4.    granuloma annulare

5.    diabetic dermopathy
6.    diabetic bullae
7.    skin tags
 

Acanthosis nigricans

This condition appears as hyperpigmented, velvety plaques on the flexural areas such as the neck and armpit. Other less commonly involved areas include the groin, sub-mammary areas and hands. Acanthosis nigricans is often associated with type 2 diabetes mellitus.

Other conditions associated with acanthosis nigricans include obesity, polycyctic ovararian syndrome (PCOS), acromegaly (a chronic disease of adults marked by enlargement of the bones of the extremities, face, and jaw that is caused by an overactive pituitary gland) and Cushing's syndrome (a disease caused by an excess of cortisol production or by excessive use of cortisol or other similar steroid hormones).

It can also be a paraneoplastic manifestation of an internal malignancy and this is termed malignant acanthosis nigricans. Acanthosis nigricans is associated with insulin resistance and the high levels of circulating insulin are thought to be the cause of acanthosis nigricans.

Treatment for this condition involves lifestyle modifications such as weight reduction and exercise. As the condition is usually asymptomatic, no treatment is required. However, lactic acid preparations and retinoic acid can be used.

Necrobiosis lipoidica

Necrobiosis lipoidica (Fig 2) presents clinically as a yellowish plaque on the shin. The edge of the plaque may be erythematous (where the redness of the skin is caused by dilatation and congestion of the capillaries, often a sign of inflammation or infection) and the plaque gradually enlarges with central atrophy.

About half of the cases of necrobiosis lipodica are associated with diabetes but it occurs in only about 0.3% of diabetics. It presents most commonly in the third decade of life where there is a degeneration of collagen in the dermis.

Treatment of this condition includes topical, intralesional or systemic steroids. Other treatments such as pentoxyphylline, aspirin, chloroquine and cyclosporin have been reported to be beneficial.

Granuloma annulare

This condition is characterised by focal degeneration of collagen. Its relation to diabetes mellitus remains uncertain but the disseminated form of disease is associated with diabetes mellitus.

It presents most commonly in children and young adults and the typical lesions comprise grouped firm flesh coloured papules arranged as a ring (Fig 3). Lesions range from 1 to 5 cm in length. The lesions usually resolve spontaneously.

Topical steroids and cryotherapy are commonly used in the treatment of this condition.

Diabetic dermopathy

This commonly presents as rashes on the shin. The skin lesions may be brownish in colour and the surface may appear slightly depressed (Fig 4).

The lesions usually resolve slowly over a period of one year but new lesions may appear even before the old lesions clear. There is usually no history of earlier injury or trauma.
 

Diabetic bullae

This is an uncommon condition and presents as spontaneous bullae over the extremities, usually in patients with a long history of diabetes. The bullae are subepidermal in location (Fig 5). No immunologic or mechanical factors have been implicated and the cause of this condition remains unknown.

These painless bullae usually heal spontaneously after two to four weeks.

Skin tags

These skin-coloured growths are commonly found on the neck, armpit and eyelids (Fig 6). Up to two thirds of the patients with skin tag may have diabetes. They are usually asymptomatic (neither causing nor showing any signs of the disease) and can be easily removed by eletrocautery.

Scleredema adultorum of Buschke

This condition presents as indurated or hardened skin on the neck and upper back and shoulders (Fig 7). There is loss of elasticity of the skin and difficulty in tenting the skin. It does not pit on firm pressure.

This condition is usually asymptomatic and requires no treatment. In more severe cases, treatments such as PUVA treatment, radiotherapy, electron beam therapy and cyclosporin have been used with some success.

Skin manifestations resulting from Diabetic treatment

Lipoatropy

This refers to a loss of subcutaneous fat which may occur at sites of injection. It is believed to be due to an immunologic reaction and is seen more commonly in females.

This side effect of lipoatrophy appears to be on the decrease with the advent of more recent purified insulin formulations.

Lipohypertrophy

This presents as an area of hypertrophy of the subcutaneous fat and is a result of repeated injections of insulin (Fig 8). This may be a result of repeated stimulation of the fat cells by insulin at the injection site.

The clinical significance is that it may lead to delayed insulin absorption. which in turn affects glycaemic control. The lipohypertrophy resolves spontaneously with avoidance of further insulin injection at the affect site.

Adverse drug reaction to the oral antidiabetic medications.

Erythema multiforme, morbilliform eruptions, lichenoid drug eruption and photosensitivity have all been reported with oral antidiabetic medication. Agents like the sulphonylureas are the most common culprits. It is important to remember that these medications contain the sulfur moiety and may cross react with other sulfur drugs.

Skin manifestations in diabetes mellitus are common and it is therefore crucial to keep your diabetes under control in order to prevent skin manifestations, especially infections. If infections are left untreated, complications may arise. It is also important that the healthcare provider recognises these skin manifestations and refers the patient to a dermatologist for further evaluation and treatment.