Table 13.
Characteristics of juvenile myositis classic autoantibody phenotypes
| Characteristic | Anti-Synthetase | Anti-SRP | Anti-Mi-2 |
|---|---|---|---|
| Demographics | |||
| Median age at diagnosis (y) | Older (14.0 years) | Oldest (15.1 years) | Older (11.0 years) |
| Race | Larger proportion non-white (47%) | Larger proportion of black patients (83%) |
Larger proportion of non-white
(82%) - mostly Hispanic |
| Severity of onset | No penchant | Severe or very severe (100%) | Mild or moderate severity (61%) |
| Delay in diagnosis | Shorter delay to diagnosis (1.9 months) | ||
| Clinical group | JDM (53%), JPM (16%), or JCTM (32%) | JPM | JDM (JDM or JDM overlap) |
| Clinical Features | Arthralgia | Distal weakness | Gottron’s papules |
| “Mechanic’s” hands | Falling episodes | Heliotrope rash | |
| Interstitial lung disease | Raynaud’s phenomenon | Malar rash | |
| Arthritis | Muscle atrophy | ||
| Raynaud’s phenomenon | Abnormal EKG or ECHO | ||
| Sclerodactyly | Dysphonia | ||
| Dyspnea at rest or on exertion | Dyspnea on exertion | ||
| Abnormal PFTs | Abnormal PFTs | ||
| Chest pain | |||
| Fever | |||
| Weight loss | |||
| Laboratory Features | Intermediate CK levels (median 3409 units/L) | Highest CK level (median 18544 units/L) |
High CK level (median 15926
units/L) |
| Intermediate levels of aldolase, LDH, AST, ALT | Highest levels of aldolase, LDH, AST, ALT | High levels of aldolase, LDH, AST, ALT | |
| Intermediate % with positive ANA (39%) | ANA negative | ANA positive (100%) | |
| Intermediate ANA titers (median 1:320) | Highest ANA titers (median 1:1280) | ||
| Outcome | Highest mortality (16.7%) | ||
| Lower percentage with calcinosis (10%) | Chronic disease course (100%) | ||
| Hospitalized (100%) | |||
| Wheelchair use (83.3%) |
Abbreviations: SRP = signal recognition particle; JDM = juvenile dermatomyositis; JPM = juvenile polymyositis; JCTM = juvenile myositis overlapping with another autoimmune or connective tissue disease; EKG = electrocardiogram; ECHO = echocardiogram; PFT = pulmonary function test
CK = creatine kinase; LDH = lactate dehydrogenase; AST = aspartate aminotransferase; ALT = alanine aminotransferase; ANA = anti-nuclear antibody.
Bold = significant in logistic regression or universally present in the group; Italicized indicates top variables from random forest models. Other variables included in this table were significant in univariable analysis. Note that random forest modeling was not performed in patients with anti-SRP and anti-Mi-2 autoantibodies.