Juvenile dermatomyositis in Child
Childhood type dermatomyositis, also known as juvenile dermatomyositis (JDM), is an idiopathic multisystem inflammatory disorder where muscle inflammation is accompanied by a skin rash. It is typically first detected in children aged between 2 and 15 years.
Cutaneous lesions may precede muscle disease by anywhere from weeks to more than 4 years and may be extremely pruritic. Exposure to sunlight may exacerbate the cutaneous lesions. 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 (UV) exposure. Patients may also have poikiloderma over the lateral hip (holster sign). Myositis (inflammation of muscle) usually develops insidiously, but sometimes abruptly, or may not occur at all (amyopathic dermatomyositis). Muscle findings include symmetric proximal muscle weakness, usually of the shoulder and pelvic girdles.
In acute phases, pain and tenderness may occur and palpation may have a doughy feel. In addition, the patient's gait may be abnormal. Patients may complain of difficulty climbing stairs and brushing their hair. Upper palatal muscle and esophageal dysfunction may be noted. Neck flexors are usually weak, and the patient may be unable to raise his or her head at all.
While children experience calcinosis cutis, muscle necrosis, and gingival and periungual telangiectasias more frequently than adults, JDM is a milder disease overall than adult dermatomyositis. There is a lower frequency of interstitial lung disease and lower overall mortality. Moreover, the association of malignancy with dermatomyositis is extremely uncommon in JDM.
Signs of severity in childhood include gastrointestinal tract involvement, high severity of muscle disease, and endomysial fibrosis on muscle biopsy. The presence of these signs may indicate disease that is refractory to first-line treatment.
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
1212005 – Juvenile dermatomyositis
- For patients with myositis, one must rule out other systemic causes of myopathy (eg, thyroid disorders, electrolyte disturbances, vitamin D deficiency, mitochondrial / metabolic myopathies, or infection) and distinguish JDM from other connective tissue diseases such as polymyositis, mixed connective tissue disease, and systemic lupus erythematosus. In childhood type dermatomyositis, fingers may appear more sausage-like than with systemic lupus erythematosus.
- Acute lesions of erythropoietic protoporphyria may have similar locations, especially on the dorsum of the hands, but usually there is no muscle weakness.
- Scalp involvement may be present in the majority of patients but is frequently misdiagnosed as psoriasis or seborrheic dermatitis.
- Hydroxyurea, simvastatin, penicillamine, NSAIDs, tryptophan, and practolol have been reported to cause dermatomyositis-like skin lesions.
- Atopic dermatitis
- Lichen planus
- Polymorphous light eruption
- Phototoxic / photoallergic drug eruptions