The skin is generally thickened in diabetes, probably because of glycation of dermal collagen and cross-linking to form advanced glycation endproducts (AGEs). Usually, this is clinically insignificant, but the combination of thickened, tight and waxy skin with limited joint mobility (cheiroarthropathy) is present in 30%–40% of type 1 diabetic patients.
This can lead to stiff and painful fingers. Thickening over the dorsum of the fingers is termed ‘Garrod’s knuckle pads’ (Figure 24.4).
A typical sign of the ‘diabetic hand syndrome’ is the ‘prayer sign,’ in which limited joint mobility because of thickened and waxy skin does not allow the patient to press their palms together (Figure 24.5).
Dupuytren’s contracture occurs in up to half of patients with diabetes, especially in the elderly and those with longstanding disease; it often co-exists with cheiroarthropathy (Figure 24.6).
‘Trigger finger’ occurs when there is intermittent locking of the finger due to stenosing flexor tenosynovitis (Figure 24.7). It is often associated with diabetes. Nodular swelling and thickening of the tendon sheath can often be palpated. It responds to steroid injection. Adhesive capsulitis of the shoulder (more often called ‘frozen shoulder’) is another non-articular fibrosing disorder that occurs more commonly in patients with diabetes than in the general population; it results in pain and limitation of movement.
Diabetic bullae are painless blisters which appear spontaneously anywhere on the feet in patients with diabetes (Figure 24.8). The lesions are rare, but occur most often over the toes and heels and seem to be more common among adult males. The blisters can range in size from a few millimetres to centimetres in diameter. There may be an association with neuropathy and retinopathy. Histologically, the lesions usually arise as intraepidermal blisters containing clear fluid, but occasionally the blisters are subepidermal. Immunofluorescent studies have failed to identify a cause.