Myra Lalas Pitt 9/26/11

 Systemic inflammatory and noninflammatory vasculopathy likely due to a combination of genetic & environmental factors  The most common pediatric inflammatory myopathy (85%)  Bimodal age distribution (ages 5–9 yr and 10–14 yr)  Incidence 0.5/100,000  ♀ : ♂ ratio 2:1  Predominance in Caucasian > Hispanics and African- American children in the US

 Symmetrical and progressive proximal muscle weakness (± dysphagia and respiratory involvement)  Calcinosis  Heliotrope rash  Scaly and erythematous dermatitis over the dorsum of the hands (Gottron's sign); involvement of the knees, elbows, medial malleoli, face, neck, and upper torso;  Nonpalpable macular rash

Seen in over 90% of patients with juvenile dermatomyositis, include dilated, tortuous capillaries and areas of capillary loss along the nailfold

 In 1975, Bohan and Peter proposed a diagnostic criteria for JDM:  Symmetrical weakness of the proximal muscles  Characteristic cutaneous changes, consisting of heliotrope dermatitis (reddish-purple rash on the upper eyelids with periorbital edema) and Gottron's papules (erythematous, papulosquamous eruption over the dorsal surfaces of the knuckles)  Elevation of the serum level of one of the muscle enzymes  Electromyography (EMG) demonstrating denervation and myopathy  Muscle biopsy displaying necrosis and inflammation

 Inherited muscular dystrophies  Metabolic abnormalities (Hypokalemia, hypocalcemia, hypercalcemia, uremia)  Mitochondrial myopathies  Endocrine: Hypothyroidism, hyperthyroidism Cushing syndrome/exogenous steroid myopathy Diabetes mellitus

 Neurologic disorders: Myasthenia gravis Guillain-Barre syndrome Multiple sclerosis Infections: Viral Lyme disease Parasitic (Trichinosis, toxoplasmosis, filariasis, trypanosoma, cysticercosis)  Autoimmune SLE JIA PAN Crohn UC Celiac disease Psoriasis

 Aims: suppress the inflammatory response prevention loss of muscle function maintain joint range of motion

 1 st line: Corticosteroids  May add: methotrexate, cyclosporine, and, in severe cases, cyclophosphamide  Hydroxychloroquine and IVIG are particularly helpful in managing the skin manifestations.  Sun protection  PT/ OT

 A 16-year-old boy presents with diffuse muscle pain and dark urine after a summer football practice. On physical examination, he appears uncomfortable, and his arm and leg muscles are painful to palpation. Of the following, the MOST likely cause of this boy's findings is

A. Bacterial abscess of the quadriceps B. Genetic mitochondrial disorder C. Inflammatory dermatomyositis D. Limb girdle muscular dystrophy E. Myositis due to influenza

 First, the event occurred after a football practice, where exercise often is extreme. Some rare mitochondrial conditions affecting energy metabolism tend to present in precisely this setting.  Second, there is the darkening of the urine. Myoglobinuria indicates rhabdomyolysis or breakdown of muscle fibers. Accordingly, the adolescent in the vignette most likely has a genetic disorder affecting mitochondrial function (carnitine palmitoyl transferase II deficiency).

 A bacterial abscess of the quadriceps would not produce diffuse pain of the arms and legs.  Inflammatory dermatomyositis presents with proximal weakness, pain, and characteristic skin findings.  Neither dermatomyositis nor limb girdle muscular dystrophy presents acutely with rhabdomyolysis.  Influenza can present with myositis, but this adolescent has been at summer football practice and had no signs of systemic illness prior to this dramatic presentation.

Lowry AW, Bhakta KY, Nag PK, "Chapter 26. Rheumatology" (Chapter). Lowry AW, Bhakta KY, Nag PK: Texas Children's Hospital Handbook of Pediatrics and Neonatology: Rider Lisa G, "Chapter 205. Juvenile Dermatomyositis" (Chapter). Colin D. Rudolph, Abraham M. Rudolph, George E. Lister, Lewis R. First, Anne A. Gershon: Rudolph's Pediatrics, 22e: Soep Jennifer B, "Chapter 27. Rheumatic Diseases" (Chapter). William W. Hay, Jr., Myron J. Levin, Judith M. Sondheimer, Robin R. Deterding: CURRENT Diagnosis & Treatment: Pediatrics, 20e: