Dermatomyositis - Nail and Distal Digit
Dermatomyositis is a connective tissue disorder with distinctive nail findings that help distinguish it from other connective tissue disorders. Thickened, hyperkeratotic, ragged cuticles and telangiectasias of the proximal nailfold (PNF) are the characteristic nail findings. Some other rare nail findings have been reported, including complete loss of several toenails, red lunulae, and ventral pterygium. The presence of ischemic lesions might be predictive of malignancy in dermatomyositis of adulthood.
In addition to the nail findings, other cutaneous findings such as periorbital heliotrope rash, atrophic dermal papules of dermatomyositis (ADPDM; formerly called Gottron papules) (slightly atrophic, flat-topped papules over the proximal interphalangeal joints), and poikiloderma should also be present. ADPDM may involve the vicinity of the PNF. Other characteristic features may include flat erythema of the upper back and posterior neck and shoulders (shawl sign) as well as a similarly presenting macular erythema of the anterior neck and upper chest (V sign) that can worsen with UV exposure. Patients may also have poikiloderma over the lateral hip (Holster sign). Muscle involvement affects proximal muscle groups in a symmetric fashion.
In 2017, the European League Against Rheumatism / American College of Rheumatology (EULAR/ACR) released new classification criteria for idiopathic inflammatory myopathies.
M33.90 – Dermatopolymyositis, unspecified, organ involvement unspecified
396230008 – Dermatomyositis
- Systemic lupus erythematosus – Violaceous color and extensor-limited skin disease not seen in lupus erythematosus. Check anti-ds DNA, anti-Sm if considering lupus erythematosus.
- Phototoxic / photoallergic drug eruptions
- CREST syndrome – Can have overlap with dermatomyositis. Refers to a subset of patients with limited scleroderma.
- Scleroderma – Check for anticentromere antibodies and anti-Scl-70 antibodies. Typified by sclerotic changes in skin not seen in dermatomyositis.
- Graft-versus-host disease – Occurs after allogeneic stem-cell transplantation.
- Mixed connective tissue disease – Check for anti-U1RNP antibody. Most patients are positive for this in mixed connective tissue disease.
- Raynaud phenomenon – No systemic involvement.
- Polymyositis – Without cutaneous findings.
- Acute lesions of erythropoietic protoporphyria may have similar locations, especially on the dorsum of the hands, but usually there is no weakness.
- Irritant dermatitis
- Atopic dermatitis
- Contact dermatitis