Dermatomyositis - Nail and Distal Digit
The distinctive nail findings of dermatomyositis help distinguish it from other connective tissue disorders. Thickened, hyperkeratotic, ragged cuticles and telangiectasias of the proximal nail fold (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 ultraviolet exposure. Patients may also have poikiloderma over the lateral hip (holster sign). Muscle involvement affects proximal muscle groups in a symmetric fashion.
Dermatomyositis may be induced by medications, including hydroxyurea, penicillamine, interferon beta, and ipilimumab. Acute onset / flares of dermatomyositis have been reported in association with ingestion of IsaLean, an herbal supplement.
M33.10 – Other dermatomyositis, organ involvement unspecified
396230008 – Dermatomyositis
- SLE – Violaceous color and extensor-limited skin disease not seen in lupus erythematosus (LE). Digital macules and thin plaques typically do not involve the knuckles but rather are seen on interdigital skin. Pruritus is not so prominent in LE. Check anti-double stranded DNA, anti-Smith if considering LE.
- 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 the skin not seen in dermatomyositis.
- Graft-versus-host disease – Occurs after allogeneic stem-cell transplantation.
- Mixed connective tissue disease – Check for anti-U1 ribonucleoprotein (RNP) 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