Dermatomyositis_0312 Derm Clin 1
A 10-year-old Hispanic girl presented with a rash that had been present for four months. Previous treatment with topical corticosteroids for atopic dermatitis provided no resolution of the rash. Examination of the hands revealed erythematous lichenified plaques distributed over the joints, along with ragged cuticles and periungual telangiectasias.
In addition, violaceous patches with areas of hypo- and hyperpigmentation along with telangiectasias were seen around the eyes, bilateral cheeks and upper trunk. Muscle strength measured of 3/5 on bilateral triceps and 4/5 on bilateral quadriceps. The girl has to sleep on the ground floor because she is too weak to walk upstairs. What’s your diagnosis?
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Dermatomyositis is characterized by a cutaneous eruption; it is manifested by an extensor, inflammatory and symmetric proximal myopathy. Polymyositis is a term used for patients whose skin is spared from disease. In contrast, dermatomyositis sine myositis (also called amyopathic dermatomyositis) is a term used for those patients who have skin disease alone.
The disease has a bimodal age distribution, ranging from age 10 to 15 years and age 45 to 57 years. Cases of infantile dermatomyositis also have been observed.1 Gender does not seem to play a role in children, but adult women are twice as likely as men to develop the disease.2 Approximately 25% of adult patients will also have an associated malignancy. Juvenile patients have no increased risk of malignancy but are at higher risk for small-vessel vasculitis and calcinosis. The incidence in various populations ranges from 2 per million to 7 per million.2
Dermatomyositis results from an immune-mediated process in genetically predisposed individuals. It is also believed that a trigger is necessary for the initiation of the disease. Potential triggers include drugs, infectious agents and malignancy.2
Drug-induced dermatomyositis has been reported due to hydroxyurea (Droxia, Hydrea) in patients with chronic myelogenous leukemia. Other drugs, such as phenytoin (Dilantin), nonsteroidal anti-inflammatories and lipid-lowering agents, have also been suspected as the trigger for dermatomyositis.2,3 Infectious agents include such viruses as HIV, coxsackievirus-9, echovirus, Escherichia coli and picornavirus. Genitourinary cancers are the most commonly diagnosed malignancies in adult patients with dermatomyositis.2
A violaceous poikiloderma is one of the most characteristic features of the disease. Poikiloderma is characterized by hyper- or hypopigmentation, telangiectasias and epidermal atrophy.2 The shawl sign is described as a poikiloderma that is seen in a characteristic distribution on the anterior neck, upper chest and back area in a V shape.
The heliotrope sign, named after its similarity to the heliotrope flower, will be visible when the poikiloderma involves the periorbital skin. Violaceous discoloration that affects such bony prominences as the knuckles, elbows and knees, is termed Gottron’s sign. When these areas develop a secondary lichenoid quality, they are called Gottron’s papules. Other clinical features include the photodistributed pattern of the rash and the presence of such nailfold changes as cuticular dystrophy and periungual telangiectasias.3 Well-defined, erythematous plaques with silvery scale may be appreciated on the extensor surfaces of the elbows and knees. Patients may complain of severe pruritus. In children, calcinosis cutis, often at sites of prior trauma, may also be seen.
The dermatologic manifestations of dermatomyositis often precede the onset of muscle disease.2 Patients may present with complaints of fatigue and malaise.4 The myositis affects proximal muscle groups in a symmetric fashion. The most commonly affected muscles are the extensors, including the triceps and quadriceps. As the disease advances, all muscle groups may become affected, and muscles may be tender to palpation.
The risk for developing a malignancy in adults with dermatomyositis ranges from 10% to 50%.2 It is important for clinicians to recognize the signs of dermatomyositis because the rash will often precede the onset of symptoms related to the cancer. Some of the most common malignancies include ovarian, colon, breast, lung, pancreatic and gastric cancers.2,5
Since the triceps and biceps are often the first to be affected by the disease, muscle biopsy should be taken from one of these areas (typically the triceps).6 The biopsy will often show type II muscle fiber atrophy, necrosis, regeneration and lymphocytes in a perifascicular and perivascular distribution.2,3
Poikiloderma is a characteristic feature of dermatomyositis but is also seen in such other diseases as lupus erythematosus. However, while the poikiloderma is violaceous in dermatomyositis, it is erythematous in lupus erythematosus.7 Histologically, dermatomyositis and lupus erythematosus may be indistinguishable. Other disorders to consider in the differential diagnosis include psoriasis, atopic dermatitis, airborne or allergic contact dermatitis, photodrug reactions, scleroderma and cutaneous T-cell lymphoma.6
Once the diagnosis of dermatomyositis is confirmed histopathologically, the search for possible muscle involvement must follow. The evaluation includes assessing the strength of the proximal extensor muscles, obtaining serum levels of muscle enzymes, and performing an electromyogram and a triceps muscle biopsy. MRI or ultrasound of the proximal muscles is often obtained prior to (or instead of) a muscle biopsy in individuals with classic dermatomyositis.2 Such additional baseline investigations as a CT scan, pulmonary function tests, electrocardiogram, evaluation for overlap connective tissue diseases and screening for occult malignancy should be done prior to starting systemic therapy.
Corticosteroid treatment should be initiated after muscle involvement is confirmed by two positive objective tests. The dose of prednisone is generally 1.0 mg/kg,but this may need to be adjusted depending on the clinical response and/or extent of muscle disease.2
If necessary, such steroid-sparing agents as methotrexate (Rheumatrex, Trexall), azathioprine (Azasan, Imuran), chlorambucil (Leukeran), pulse cyclophosphamide (Cytoxan), cyclosporine (Gengraf, Neoral, Sandimmune, Sangcya), fludarabine (Fludara), mycophenolate mofetil (CellCept, Myfortic), tacrolimus (Hecoria, Prograf), sirolimus (Rapamune), infliximab (Remicade) and rituximab (Rituxan) may be used alone or in conjunction with the corticosteroid.2
The patient in this case was found to have elevated levels of creatine kinase and aldolase and abnormal electromyography results. A biopsy of the triceps muscle showed changes that were classic for dermatomyositis. Treatment with high-dose prednisone led to resolution of the myositis and no recurrence to date. The dermatologic manifestations of this patient’s disease were treated with triamcinolone 0.1% ointment b.i.d., as needed for pruritus. The rash has improved but has not completely resolved.
Kerri Robbins, MD, is a resident in the Department of Dermatology at Baylor College of Medicine in Houston. The author has no relationhsips to discolse relating to the content of this article.
1. Pachman LM, Hayford JR, Chung A et al. “Juvenile dermatomyositis at diagnosis: clinical characteristics of 79 children.” J Rheumatol. 1998;25:1198-1204.
2. Bolognia JL, Jorizzo JL, Rapini RP eds. Dermatology. 2nd ed. St. Louis, Mo.: Elsevier-Mosby; 2008:575-583.
3. Habif TP. Skin Disease: Diagnosis and Treatment. 2nd ed., Philadelphia, Pa.: Elsevier Mosby; 2005:350-353.
4. RP Rapini. Practical Dermatopathology. Philadelphia, Pa.: Elsevier Mosby; 2005:228-229.
5. Barnes BE, Mawr B. “Dermatomyositis and malignancy. A review of the literature.” Ann Intern Med. 1976;84:68-76.
6. Elder DE, Elenitsas R, Johnson BL et al, eds. Lever’s Histopathology of the Skin. 10th ed. Philadelphia, Pa.: Lippincott Williams & Wilkins; 2009:293-295.
7. Fitzpatrick TB, Johnson RA, Wolff K, Suurmond R, eds. Color Atlas and Synopsis of Clinical Dermatology, 5th ed. New York, N.Y.: McGraw-Hill; 2005:372-374.