CHAPTER 75

Autoimmune Connective Tissue Diseases

Overview

• Genetic background as well as additional immunogenic, environmental, and hormonal factors may influence the development of autoimmune connective tissue diseases (CTDs); however, the pathophysiologic processes of most autoimmune CTDs are not well understood.

• This chapter includes the most common autoimmune CTDs with musculoskeletal signs and symptoms.

Systemic Lupus Erythematosus

INTRODUCTION/ETIOLOGY/EPIDEMIOLOGY

• Systemic lupus erythematosus (SLE) has an annual incidence of 0.3 to 0.9 per 100,000 children in the United States.

• Fifteen percent to 20% of all cases present during the first 2 decades after birth, with peak incidence during early adolescence.

• Females are more often affected than males

— 8 to 9:1 (pubertal and postpubertal)

— 4 to 5:1 (prepubertal)

• SLE is more common among Black, Latino, Asian, and Indigenous North American persons than white persons.

SIGNS AND SYMPTOMS

• Thirty percent of pediatric patients present with the 4 early features

— Fatigue

— Low grade, persistent fever (the most common sign of SLE)

— Arthralgias

— Malar rash: erythematous patch across the nasal bridge, sparing the nasolabial folds

■Malar rash may not be as easily seen in those with darker skin pigmentation

• Some will have scaly, discoid lesions throughout the body that appear similar to the rash of a drug reaction.

Box 75-1. Differential Diagnosis of Systemic Lupus Erythematosus

DIFFERENTIAL DIAGNOSIS

• See Box 75-1.

DIAGNOSTIC CONSIDERATIONS

• Diagnosis of SLE is established clinically based on new criteria published in 2019 by the American College of Rheumatology (ACR) and the European Alliance of Associations for Rheumatology (EULAR [formerly the European League against Rheumatism]) (Tables 75-1 and 75-2):

— The ACR/EULAR classification requires a positive antinuclear antibody (ANA) titer of at least 1:80 on HEp-2 cells or an equivalent positive test result.

— If there is a positive ANA test result or previous history of a positive test result, then 22 “additive weighted” classification criteria are considered to determine the diagnosis.

■Seven clinical domains: constitutional, hematological, neuropsychiatric, mucocutaneous, serosal, musculoskeletal, renal

■Three immunologic domains: antiphospholipid antibodies, complement proteins, SLE-specific antibodies.

■Each criterion is assigned points, ranging from 2 to 10.

■Patients with at least 1 clinical criterion and 10 or more points are classified as having SLE.

— The EULAR/ACR criteria have sensitivity of 96.1% and specificity of 93.4%.

Table 75-1. European Alliance of Associations for Rheumatology/ American College of Rheumatology Clinical Domains and Criteria for Systemic Lupus Erythematosus^a

^a A criterion should not be counted if there is a more likely explanation for it than systemic lupus erythematosus. Occurrence of a criterion on at least one occasion is sufficient. Criteria need not occur simultaneously. Within each domain, only the highest-weighted criterion is counted toward the total score.

Reprinted with permission from Aringer M, Costenbader K, Daikh D, et al. 2019 European League Against Rheumatism/American College of Rheumatology classification criteria for systemic lupus erythematosus. Arthritis Rheumatol. 2019;17(9):1400–1412.

• Laboratory studies used in the diagnosis of SLE are as follows: CBC with differential, serum creatinine, urinalysis with microscopy, ESR or CRP level, complement levels, liver function tests, creatine kinase assay, spot protein/spot creatinine ratio, autoantibody tests

TREATMENT

• Early initiation of treatment improves disease outcome; therefore, these children should be promptly referred to a pediatric rheumatologist when appropriate screening suggests SLE.

• Mild disease can be managed with high-dose nonsteroidal anti-inflammatory drugs (ibuprofen and naproxen).

• Hydroxychloroquine has been shown to be effective for mild to moderate flares of joint swelling and skin rashes.

Table 75-2. European Alliance of Associations for Rheumatology/ American College of Rheumatology Immunologic Domains and Criteria for Systemic Lupus Erythematosus^a

^a A criterion should not be counted if there is a more likely explanation for it than systemic lupus erythematosus (SLE). Occurrence of a criterion on at least one occasion is sufficient. Criteria need not occur simultaneously. Within each domain, only the highest-weighted criterion is counted toward the total score.

Reprinted with permission from Aringer M, Costenbader K, Daikh D, et al. 2019 European League Against Rheumatism/American College of Rheumatology classification criteria for systemic lupus erythematosus. Arthritis Rheumatol. 2019;17(9):1400–1412.

• Severe disease involving major organs or lupus crisis requires immunosuppression. Corticosteroids are first-line therapy, and low doses can suppress mild to moderate symptoms; however, controversy exists regarding timing and introduction because of toxic side effects.

• Complex disease including severe arthralgias, pancytopenia, hypercholesterolemia, acute renal disease, and hypertension requires additional treatment and frequent monitoring.

EXPECTED OUTCOMES/PROGNOSIS

• Ten-year survival rate has improved from 30% in 1970 to close to 90% with current management protocols.

• Most patients endure chronic “lupus crises,” exacerbation periods that can involve acute renal failure and malignant hypertension.

• Infantile SLE (onset at younger than 2 years) is associated with the most severe course.

• Less than 5% of pediatric cases experience mild disease.

• Laboratory markers reporting ribosomal protein (anti-P) and anti-ds DNA indicate a poor prognosis.

• Lupus nephritis is the strongest predictor of poor outcome. Forty percent of patients are diagnosed with nephritis at onset, while 60% to 70% manifest nephritis during the course of the disease. Patients with anti-ds DNA and decreasing complement levels are more likely to have renal involvement.

• Systemic comorbidities include neurocognitive dysfunction, pulmonary manifestations, and cardiovascular complications, including pericarditis, endocarditis, and accelerated atherosclerosis.

• Corticosteroid therapy for chronic disease combined with reduced sun exposure has resulted in decreased adolescent bone mass and increased risk for osteopenia and osteoporosis.

PREVENTION

• Pediatricians should educate patients with autoimmune CTDs to avoid sun exposure, use sunscreen, and wear clothing that is UV protectant to decrease the risk of photoexacerbation.

• Patients should also be educated to avoid tobacco, consume a low-fat diet, and engage in regular physical activity to increase bone density and decrease the risk for accelerated atherosclerosis.

• Expectant mothers with autoimmune CTDs should be educated and followed regularly throughout pregnancy, as this population has been identified to have a higher incidence of preeclampsia, preterm deliveries, and postpartum renal failure. Infants born to mothers with autoimmune CTDs may be at increased risk for autoimmune CTD secondary to passive transfer of autoantibody across the placenta.

WHEN TO REFER

• Suspected cases of SLE should be promptly referred to a pediatric rheumatologist.

• Early referral for renal and cerebral lupus allows aggressive therapeutic approach and leads to decreased morbidity. Ten-year survival rate for pediatric renal disease approaches 100% secondary to early referral and frequent monitoring of renal function.

RESOURCES FOR PHYSICIANS AND FAMILIES

• Lupus Foundation of America provides resources to patients with lupus, including a directory of local chapters and a calendar of upcoming events (www.lupus.org).

Juvenile Dermatomyositis

INTRODUCTION/ETIOLOGY/EPIDEMIOLOGY

• Juvenile dermatomyositis (JDM) is a rare systemic vasculopathy, primarily involving the skin and muscle.

•

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