The most likely diagnosis is amyopathic dermatomyositis. This patient has a clinical presentation of heliotrope eruption in the form of a violaceous periorbital rash, Gottron papules over the extensor surface of small joints of the hands, and photodistributed violaceous poikiloderma (V sign and Shawl sign) without muscle weakness. These are findings of skin involvement seen in dermatomyositis without any clinical, serum, or electromyogram (EMG) findings of muscle involvement or myositis, suggesting the diagnosis of amyopathic dermatomyositis. Amyopathic dermatomyositis is seen in about 20% to 25% of patients with dermatomyositis, but some of these patients have evidence of myositis on one of the evaluation studies (muscle enzymes, EMG, or muscle biopsy) in the absence of muscle weakness. To qualify for the diagnosis of amyopathic dermatomyositis, the patient should have the characteristic rash but no clinical, laboratory, or muscle evaluation findings of myositis. Amyopathic dermatomyositis may be triggered by sunlight exposure and also is associated with an underlying malignancy. Treatment is usually with glucocorticoids and immunosuppressive agents.

Polymorphous light eruption (PMLE) is another dermatologic condition in which patients develop skin lesions after exposure to sunlight; these lesions last several days and resolve spontaneously in the absence of reexposure. A variety of skin lesions may be seen in PMLE, including urticarial wheals, papules, plaques, and vesicles. PMLE usually develops early in the spring, with the first few exposures to sunlight, and can be triggered by intense exposures. These lesions occur in photodistributed areas but lack characteristic heliotrope or Gottron eruptions. A diagnosis of PMLE is unlikely in this patient.

Rosacea is a chronic, inflammatory condition that causes an acneiform eruption and flushing on the mid-face. There are two types, vascular and papular pustular (inflammatory) rosacea. Vascular rosacea presents as persistent flushing, especially of the central face, with prominent telangiectasias. Pustules and papules are seen in the inflammatory variant, but in contrast to acne, rosacea pustules are not follicular based. The patient's findings are not consistent with rosacea.

Although this patient has positive antinuclear antibodies, she lacks the associated findings of systemic lupus erythematosus (SLE), including malar/discoid rash, arthritis, organ involvement, and kidney disease. SLE can cause a rash on the hands similar to Gottron papules, but it more typically involves skin located between the joints.