Skin Findings in Dermatomyositis

Skin findings — Several distinct cutaneous eruptions, which are generally evident at the time of clinical presentation, occur in DM but not in PM . Other skin changes may occur in patients with PM and in patients with DM and are not specific to either disorder. Dermatologic manifestations may be prominent but can be quite subtle in some patients.

Characteristic dermatomyositis findings — Gottron's papules and the heliotrope eruption are the hallmark and likely pathognomonic features of DM. Gottron's sign, photodistributed erythema, poikiloderma, nailfold changes, scalp involvement, and calcinosis cutis are also characteristic and useful in distinguishing DM from PM.

●Gottron's papules – Gottron's papules are erythematous to violaceous papules that occur symmetrically over the extensor (dorsal) aspects of the metacarpophalangeal (MCP) and interphalangeal (IP) joints (picture 1A-C). In addition, these lesions may involve the skin between the MCP and IP joints, particularly when the eruption is prominent. Gottron's papules often have associated scale and may ulcerate. When scaling is present, the lesions may mimic psoriasis or lichen planus.

●Gottron's sign – Definitions used for Gottron's sign have varied in the literature. We define Gottron's sign as the presence of erythematous to violaceous macules, patches, or papules on the extensor surfaces of joints in sites other than the hands, particularly the elbows, knees, or ankles. By contrast, some authors have used the term Gottron's papules to refer to papules in these areas, reserving Gottron's sign for macular or patch-like lesions (picture 2) .

●Heliotrope eruption – The heliotrope eruption is an erythematous to violaceous eruption on the upper eyelids, sometimes accompanied by eyelid edema, which, at times, may be quite marked .

●Facial erythema – Patients may have midfacial erythema that can mimic the malar erythema seen in SLE . In contrast to those with SLE, patients with DM will often have involvement of the nasolabial fold, which can be helpful in distinguishing these two photosensitive midfacial eruptions.

●Photodistributed poikiloderma (including the shawl and V signs) – Poikiloderma refers to skin that demonstrates both hyperpigmentation and hypopigmentation, as well as telangiectasias and epidermal atrophy. In DM, patients may demonstrate poikiloderma in any photo-exposed site; however, classic areas of involvement are the upper back (shawl sign) and the V of the neck and upper chest. The poikiloderma in DM often presents with a violaceous hue. Early in the course of cutaneous disease, these areas may demonstrate only erythema rather than well-developed poikiloderma . The erythema may be macular (nonpalpable) or papular. In rare patients, these lesions become thickened and resemble papular mucinosis. The cutaneous eruption of DM is often associated with significant pruritus, which may assist in distinguishing its photo-exacerbated eruption from that of lupus erythematosus (LE).

●Holster sign – Patients with DM may also have poikiloderma on the lateral aspects of the thighs, referred to as the "Holster sign" . It is unclear why this cutaneous manifestation occurs on this classically photo-protected site.

●Generalized erythroderma – In rare patients, erythroderma may occur, which involves extensive cutaneous surface area, including areas that are less exposed to ultraviolet light.

●Periungual abnormalities – The capillary nail beds in DM may be erythematous and may show vascular changes similar to those observed in other systemic rheumatic diseases (eg, scleroderma and SLE). Abnormal capillary nail bed loops may be evident, with alternating areas of dilatation and dropout and with periungual erythema . In addition, cuticular overgrowth, sometimes termed "ragged cuticles," is characteristic and may be associated with hemorrhagic infarcts within the hypertrophic area . The degree of cuticular involvement is thought to reflect ongoing cutaneous disease activity, representing active vasculopathy .

●Psoriasiform changes in scalp – Changes in the scalp resembling seborrheic dermatitis or psoriasis occur in a high percentage of patients with DM . The scalp involvement in DM is diffuse, often associated with poikilodermatous changes and with prominent scaling. Scalp involvement may result in severe burning, pruritus, and/or sleep disturbance. In addition, severe pruritus may occur in patients without visible disease.

●Calcinosis cutis – The deposition of calcium within the skin, a finding known as calcinosis cutis, occurs commonly in juvenile DM. It is infrequent in adult DM. In children, calcinosis has been associated with a delay in treatment with glucocorticoids and/or immunosuppressive therapy. Calcinosis cutis, which is known to be very challenging to treat, may be seen in a variety of conditions, including SSc, particularly limited cutaneous SSc; SLE (rarely); and overlap connective tissue disorders. It may be more common in patients with DM with the anti-p140/anti-MJ autoantibody

Bhopalwala. H