Table 2.
Cumulative features of SSc and myositis in high-titre anti-SMN+ compared to anti-SMN− MCTD patients
| All patients (n=66) |
MCTD anti- SMN+ high titre (n=29) |
MCTD anti- SMN− (n=27) |
|
| Female sex, n (%) | 58 (88) | 27 (93) | 22 (81) |
| Race, n (%) | |||
| White | 59 (89) | 27 (93) | 22 (81) |
| Black | 4 (6) | 2 (7) | 2 (7) |
| Other | 3 (5) | 0 (0) | 3 (11) |
| Smoker, n (%) | 30/60 (50) | 15/25 (60) | 13/26 (50) |
| Age at diagnosis, median (range), years | 40.6 (10.7–70) | 39.5 (14.4–70) | 42.1 (21.3–61.4) |
| Duration of follow-up, median (range), years | 12 (0–42.4) | 10.2 (0–42.4) | 13.9 (0–39.8) |
| Speckled ANA ≥1:1280, n (%) | 66 (100) | 29 (100) | 27 (100) |
| Median anti-SMN value (range), MFI | 451 (40–15397) | 7727 (1143–15397) | 98 (40–281) |
| Positive anti-Sm antibody | 13/62 (21) | 7/26 (27) | 2 (7) |
| Positive anti-dsDNA antibody | 19/65 (29) | 7 (24) | 9/26 (35) |
| MCTD classification, n (%) | |||
| Alarcón-Segovia criteria | 57 (86) | 26 (90) | 23 (85) |
| Kahn criteria | 48 (73) | 23 (79) | 19 (70) |
| Kasukawa criteria | 64 (97) | 29 (100) | 25 (93) |
| Tanaka criteria | 65 (98) | 29 (100) | 26 (96) |
| Definite SSc†, n (%) | 47 (71) | 22 (76) | 17 (63) |
| Definite SLE‡, n (%) | 54 (82) | 23 (79) | 23 (85) |
| Definite SS§, n (%) | 8 (12) | 5 (17) | 3 (11) |
| SSc features, n (%) | |||
| Sine scleroderma | 17 (26) | 5 (17) | 8 (30) |
| Skin thickening proximal to MCP | 11 (17) | 9 (31)* | 2 (7)* |
| Sclerodactyly distal to MCP, proximal to PIP | 49 (74) | 24 (83) | 19 (70) |
| Raynaud phenomenon | 65 (98) | 29 (100) | 27 (100) |
| Abnormal nailfold capillaroscopy | 34/46 (74) | 16/20 (80) | 11/18 (61) |
| Puffy fingers | 43/64 (67) | 21/27 (78) | 17 (63) |
| Digital tip ulcers | 21 (32) | 10 (34) | 6 (22) |
| Fingertip pitting scars | 10 (15) | 7 (24)** | 1 (4)** |
| Telangiectasias | 43 (65) | 19 (66) | 18 (67) |
| Calcinosis | 17 (26) | 9 (31) | 7 (26) |
| Pulmonary arterial hypertension¶ | 17/51 (33) | 10/20 (50) | 5/22 (23) |
| Interstitial lung disease†† | 22/56 (39) | 7/22 (32) | 11/26 (42) |
| DLCO <70% | 33/50 (66) | 14/19 (74) | 12/22 (55) |
| Oesophageal dysmotility | 38/63 (60) | 20 (69) | 14/26 (54) |
| GERD/dyspepsia | 54/60 (90) | 24/25 (96) | 21/26 (81) |
| Pneumatosis | 3 (5) | 3 (10) | 0 (0) |
| Pseudo-obstruction | 6 (9) | 5 (17) | 1 (4) |
| Small intestinal bacterial overgrowth | 11 (17) | 8 (28)*** | 1 (4)*** |
| Scleroderma renal crisis | 1 (2) | 0 (0) | 0 (0) |
| Inflammatory myositis features, n (%) | |||
| Myositis diagnosis | 18/65 (28) | 11 (38) | 4 (15) |
| DM diagnosis | 3/65 (5) | 1 (3) | 2 (7) |
| Myocarditis | 6/65 (9) | 6 (21)**** | 0 (0)**** |
| Elevated serum CK levels (CK >170 UI/L) | 24/65 (37) | 12 (41) | 8 (30) |
| Median CK level, if CK >170 UI/L (range) | 938 (185–6000) | 1419 (233–6000) | 1152.5 (190–2980) |
Bold values are statistically significant variables.
*p-value 0.04.
**p-value 0.05.
***p-value 0.03.
****p-value 0.02.
†Definite SSc criteria: score of ≥9 (American College of Rheumatology (ACR)/EULAR 2013)11.
‡Definite SLE criteria: score of ≥10 (ACR/EULAR 2019)12.
§Definite SS criteria: score of ≥4 (ACR/EULAR 2016)13.
¶Pulmonary arterial hypertension defined as systolic pulmonary arterial pressure (PAP) ≥35 mm Hg on transthoracic echocardiogram or mean PAP ≥25 mm Hg on right heart catheterisation.
††Interstitial lung disease based on thoracic CT scan.
ANA, antinuclear autoantibodies; CK, creatine kinase; DLCO, diffusing lung capacity for carbon monoxide; DM, dermatomyositis; dsDNA, double stranded DNA; GERD, gastro-oesophageal reflux disease; MCP, metacarpophalangeal; MCTD, mixed connective tissue disease; PIP, proximal interphalangeal; RNP, ribonucleoprotein; SLE, systematic lupus erythematosus; Sm, Smith; SMN, survival of motor neuron; SS, Sjögren syndrome; SSc, systemic sclerosis.