Clinical characteristics and symptom progression of dermatomyositis subtypes: A retrospective analysis of a prospective database

BACKGROUND

Disease characteristics of classic dermatomyositis (DM) and clinically amyopathic DM (CADM) are well established, but there exists limited knowledge on the disease progression of these subtypes.

OBJECTIVE

The objective of this study was to longitudinally track and characterize classic DM and CADM patients who experience changes in disease presentation.

METHODS

We conducted a retrospective review of prospectively collected data on 269 DM patients from a longitudinal database.

RESULTS

A total of 51% of the patients had classic DM and 49% had CADM. Forty percent of the classic DM patients became postmyopathic (PmDM). Median Cutaneous Dermatomyositis Disease Area and Severity Index activity (CDASI-A) score was lower in PmDM patients than in classic DM patients (13.0 vs 16.0), but 45% of the PmDM patients had CDASI-A scores > 14. Five percent of the CADM patients developed muscle involvement. Compared with CADM patients, those who developed muscle symptoms had milder skin disease before subtype conversion (median CDASI-A 12.0 vs 16.0) and at subtype conversion (median CDASI-A 9.0 vs 16.0).

LIMITATIONS

This was a retrospective study conducted at a single tertiary-care dermatology clinic.

CONCLUSIONS

Forty percent of the classic DM patients became PmDM. The majority continue with muscle disease, and many continue to have moderate/severe skin disease. CADM has a low risk of progressing to muscle disease, with the extent of skin disease as a potential predictive factor.

Comparison of characteristics and anti-MDA5 antibody distribution and effect between clinically amyopathic dermatomyositis and classic dermatomyositis: a retrospective case-control study

Background

Clinically amyopathic dermatomyositis (CADM) is a distinct subtype of dermatomyositis (DM) characterized by typical DM cutaneous findings but with minimal or no evidence of myositis. It possesses unique features different from classic DM (CDM). Anti-melanoma differentiation-associated gene 5 (MDA5) antibodies were found in CADM and are thought to increase the risk of rapidly progressive interstitial lung disease (RP-ILD) and are present in both CADM and CDM patients, affecting their condition and prognosis. Nevertheless, no large-sample studies have compared all aspects concerning patients with CADM and those with CDM. This study aimed to investigate differences in clinical characteristics and risk factors for mortality between CADM and CDM and to clarify the distribution and impact of anti-MDA5 antibodies in patients with these conditions.

Methods

A retrospective case-control study included 330 patients and collected and analyzed their clinical data from The First Affiliated Hospital of Shandong First Medical University and Shandong Provincial Hospital of Traditional Chinese Medicine between January 2015 and July 2022; all patients were followed up to evaluate changes in their condition and prognosis. Several new cohorts were designed around anti-MDA5 antibodies to explore their distribution and impact in CADM and CDM.

Results

We found CADM to be associated with higher rates of mortality, 1-year mortality, interstitial lung disease (ILD), and RP-ILD than CDM. In CADM, RP-ILD, anti-MDA5 antibodies, and high ferritin and lactate dehydrogenase (LDH) levels were identified as independent risk factors for death. In CDM, the neutrophil-to-lymphocyte ratio, anti-MDA5 antibodies, and high ferritin levels were shown to be independent risk factors for death, whereas mechanic's hand was considered a protective factor against it. Anti-MDA5 antibody-positive patients did not exhibit any significant difference based on whether they belonged to the CADM or CDM groups. When no anti-MDA5 antibody-positive patients participated, the ferritin levels and rates of RP-ILD and ILD were still higher in CADM than in CDM; however, such differences decreased, whereas the LDH levels, rates of mortality, and 1-year mortality did not differ. Anti-MDA5 antibody-positive patients consistently showed higher LDH and ferritin levels, lower lymphocyte levels, higher probability of RP-ILD and ILD, and worse prognosis than anti-MDA5 antibody-negative patients, irrespective of whether the patients had DM, CADM, or CDM.

Conclusion

Patients with CADM exhibit relatively worse symptoms, serological findings, and prognosis than those with CDM. Furthermore, patients with CADM and those with CDM have commonalities and differences in risk factors for death. Moreover, CADM may necessitate earlier and more aggressive treatment strategies than CDM. Anti-MDA5 antibodies occur at a high level in patients with CADM, not only affecting the symptoms and prognosis of DM but also having a non-negligible impact on the differences between CADM and CDM. Hence, screening for anti-MDA5 antibodies in patients with CADM and CDM is extremely essential.