Finger-to-Palm Distance Among Potential Indicators of Skin Thickening, Early-Onset Systemic Sclerosis

Several factors may assistant in early detection or progression prediction of early-onset severe systemic sclerosis, or scleroderma, in Japanese patients, according to a study published in the Japanese Dermatological Association's Journal of Dermatology.¹

Finger-to-palm distance may be an effective measurement of skin thickening, researchers noted.

Image Credit: DermNet; Te Whatu Ora Health New Zealand

Background and Methods

Within 3 years of systemic sclerosis onset, it is estimated that a significant amount of patients (45% to 55%) experience severe organ involvement. According to a 2001 study published in Arthritis and Rheumatology, 19% of patients with scleroderma (n=953) went on to develop kidney involvement, 15% developed heart involvement, and 16% developed lung involvement.²

Of patients who experience severe organ involvement, the cumulative survival rate was significantly lower (38%) after 9 years versus patients with scleroderma and no severe organ involvement (72%).²

Using these critical factors and concerns as a basis, researchers conducted a 12-year study of Japanese patients from January 2002 to April 2013 in order to assess skin sclerosis progression, lung function, and disability outcomes.

The study included 207 patients from Japan with systemic sclerosis, of whom 115 were followed for a minimum of 4 years. The cohort predominantly consisted of women (75.7%), with a median age of 52 years at disease onset. The majority of patients (78.3%) presented with diffuse cutaneous systemic sclerosis, while 21.7% had limited cutaneous systemic sclerosis, some of whom also had interstitial lung disease.

Findings

At baseline, the median Modified Rodnan Skin Score (mRSS) was 19. Over the 4-year study period, this score improved to a median of 9. Multiple regression analysis identified 2 key predictors for the mRSS after 4 years: the baseline mRSS and the initial finger-to-palm distance.

Specifically, a higher initial mRSS and greater finger-to-palm distance were associated with greater skin thickening over time. This suggests that early skin involvement and limitations in hand function are critical indicators of long-term disease progression in systemic sclerosis.

Researchers assessed lung function using the percentage predicted vital capacity (%VC). The median %VC decreased from 96.4% at baseline to 91.0% after 4 years. Factors predictive of %VC decline included the baseline %VC and the presence of anti-topoisomerase I antibodies.

Notably, a lower baseline %VC was associated with a greater decline over time, while the presence of anti-topoisomerase I antibodies had a negative impact on %VC. These findings highlight the importance of early lung function metrics and autoimmune markers in predicting long-term respiratory outcomes in systemic sclerosis.

The Health Assessment Questionnaire Disability Index (HAQ-DI) score, reflecting patient-reported disability, remained relatively stable throughout the study period. However, initial HAQ-DI scores and baseline %VC were significant predictors of disability after 4 years.

Higher initial HAQ-DI scores were associated with greater long-term disability, whereas a higher baseline %VC was linked to less disability over time. This indicates that early functional status and lung capacity are important predictors of future disability in individuals with systemic sclerosis.

Digital ulcers, a common and painful complication of systemic sclerosis, were present in 17.4% of patients at baseline. This prevalence increased to 24.3% over the duration of 4 years. Factors predicting the development of digital ulcers included the presence of digital ulcers at the initial visit, baseline finger-to-palm distance, and digital pitting scars.

The presence of digital ulcers at study registration and a larger finger-to-palm distance were associated with a higher risk of developing new digital ulcers.

Conclusions

The study may have been limited by a limited number of cases, correlating with a lack of sufficient data on capillaroscopy findings. Researchers also noted that it may be worth examining all with early systemic sclerosis, as cases may further progress regardless of early severity.

"The incidence of digital ulcers within 4 years was associated with the initial finger-to-palm distance and the presence of digital ulcers, digital pitting scars, and anti-topoisomerase I antibodies," according to study authors Uesugi-Uchida et al. "The finger-to-palm distance may be a useful technique for predicting not only the mRSS, but also the occurrence of digital ulcers."

Study authors called for additional studies of a larger nature, noting they are actively engaged in a multicenter registry in Japan that will assess symptom progression and treatment shifts in patients with this condition.

References

1. Uesugi-Uchida S, Fujimoto M, Asano Y, et al. Predictors of clinical features in early-onset severe systemic sclerosis: an analysis from a multicenter prospective observational Japanese cohort. J Dermatol. September 5, 2024. https://doi.org/10.1111/1346-8138.17403
2. Steen VD, Medsger TA Jr. Severe organ involvement in systemic sclerosis with diffuse scleroderma. Arthritis Rheum. 2000; 43: 2437–2444.