Juvenile dermatomyositis

Juvenile dermatomyositis (JDM) is perhaps the most uniform, in terms of clinical and histopathological features, of the whole PM/DM disease complex. Presentation may be before 5 years of age with peak incidence between 8 and 12 years. The disease may remit and recur until well into young adult life. The skin lesions include a facial rash in butterfly distribution across nose and cheeks. Erythematous skin changes are seen over extensor surfaces of joints, especially knees, knuckles and elbows. Muscle involvement is generally evident some time later and takes the form of weakness and stiffness, particularly affecting shoulder and pelvic musculature. Proximal muscles are often worse affected than distal muscles and extensors worse than flexors. In the absence of prompt and effective treatment contractures may occur at elbows, ankles, knees, and hips. Subcutaneous calcification and skin ulceration may be found calcification of deeper-lying connective tissue may be apparent on X-ray. 

Figure 18. (a) Immunocytochemical labeling of B-lymphocytes in muscle from a patient with juvenile dermatomyositis. (b) Immunocytochemical labeling of T8 lymphocytes showing that the infiltrate contains very few cells of this type (serial section). 

Figure 19. Juvenile dermatomyositis, showing atrophy of perifascicular fibers and strong reactivity for MHC-I antigen in these fibers.

Fall N, Bove KE, Stringer K, et al. Association between lack of angiogenic response in muscle tissue and high expression of angiostatic ELR-negative CXC chemokines in patients with juvenile dermatomyositis possible link to vasculopa-thy. Arthritis Rheum 2005 52(10) 3175-3180. 

Mendez EP, Lipton R, Ramsey-Goldman R, Roettcher P, Bowyer S, Dyer A, Pachman LM (2003) NIAMS Juvenile DM Registry Physician Referral Group. US incidence of juvenile dermatomyositis, 1995-1998 results from the National Institute of Arthritis and Musculoskeletal and Skin Diseases Registry. Arthritis Rheum, 49(3) 300-305. 

Manlhiot C, Tyrrell PN, Liang L, Atkinson AR, Lau W, Feldman BM. Safety of intravenous immunoglobulin in the treatment of juvenile dermatomyositis adverse reactions are associated with immunoglobulin A content. Pediatrics 2008 121(3) e626-30. 

Glemenz MR, McGowan Iv JW, Shuler MJ, Lynn AW. Intravenous immrmoglobuHn-induced hemolytic anemia in a patient with juvenile dermatomyositis. J Drugs Dermatol JDD January 2013 12(l) lll-3. 

The incidence of these syndromes seems to vary according to geographical area and ethnic background but is about 0.2-0.3 per 100,000.population (mean annual incidence rate). However incidence rates calculated for adult populations are up to three times higher. The fifth and sixth decades show peak incidence rates and there is also clear biomodality across the full age spectrum due to the existence of a juvenile form of dermatomyositis (JDM) which is pathogenetically distinct. Polymyositis, uncomplicated by skin changes, can also occur as a juvenile condition. 

The autoimmune rheumatic diseases consists of Rheumatoid Arthritis (RA), Spondylarthritis (SpA), Systemic Lupus Erythematosus (SLE), Polymyositis, Dermatomyositis, Polymyalgia Rheumatica, Acute Temporal Arteritis, Giant Cell Arteritis, Behcet s Disease, Sjorgren s Syndrome, Felty s Syndrome and Mixed Connective Tissue Disease (MCTD). Spondylarthritis (SpA) can be subdivided in Reactive Arthritis (ReA), Ankylosing Spondylitis (AS), Psoriatic Arthritis (PsA), Arthritis associated with the inflammatory bowel diseases are Crohn s disease and Ulcerative Colitis (IBD), Undifferentiated SpA (UspA) and Sacro-ilitis, Juvenile SpA and Acute Anterior Uveitis (AAU). 

Cyclosporine is approved for use in rheumatoid arthritis and retards the appearance of new bony erosions. Its usual dosage is 3-5 mg/kg/d divided into two doses. Anecdotal reports suggest that it may be useful in systemic lupus erythematosus, polymyositis and dermatomyositis, Wegener s granulomatosis, and juvenile chronic arthritis. 

Although the most common methotrexate dosing regimens for the treatment of rheumatoid arthritis are 15 or 17.5 mg weekly, there is an increased effect up to 30 or 35 mg weekly. The drug decreases the rate of appearance of new erosions. Evidence supports its use in juvenile chronic arthritis, and it has been used in psoriasis, psoriatic arthritis, polymyositis, dermatomyositis, Wegener s granulomatosis, giant cell arteritis, subacute lupus erythematosus, and vasculitis. 

Raynaud s phenomenon secondary to systemic sclerosis Cardiac transplants Juvenile rheumatoid arfliritis polymyositis/dermatomyositis infection prophylaxis in pediatric patients with HIV acute myocarditis Tumor detection Diagnosis of myocarditis... 

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