Diminished Finger Creases in Inclusion Body Myositis
Diminished distal dorsal finger crease is associated with handgrip weakness in inclusion body myositis
Matthew N. Prinsen MD1, Ava Yun Lin MD2, Kevin Dooley MD3, Conrad C. Wei MD, PhD4, Leo H. Wang MD, PhD5
- Department of Neurology, University of Washington, Seattle, Washington.
- University of Washington Medical Center, Box 356465, 1959 NE Pacific Street, Seattle, WA 98195-6465
- Department of Pediatrics, University of Michigan
- Cure IBM, Davis, CA
- Department of Neurology, Washington University in St. Louis
OPEN ACCESS
PUBLISHED: 31 July 2025
CITATION: Preston, M.K., et al., 2025. Diminished distal dorsal finger crease is associated with handgrip weakness in inclusion body myositis. Medical Research Archives, [online] 13(7).
https://doi.org/10.18103/mra.v13i7.6773
COPYRIGHT © 2025 European Society of Medicine. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
DOI https://doi.org/10.18103/mra.v13i7.6773
ISSN 2375-1924
Abstract
Background: Sporadic inclusion body myositis (IBM) is the most common acquired myopathy in populations over age 45. This disorder causes slowly progressive asymmetric weakness with a predilection for weakness in knee extensions and in finger flexion, particularly in flexor digitorum profundus and flexor pollicis longus in the upper extremities.1 Though this clinical phenotype of IBM is relatively unique, the diagnosis can be missed without a high index of suspicion, or mistaken for amyotrophic lateral sclerosis (ALS), which can also be an asymmetric progressive motor weakness.2 Diagnosis of IBM remains challenging, with an average delay in diagnosis of 5.6 years after symptom onset.3
Methods: We examined distal dorsal finger creases in 32 patients with IBM and 44 controls.
Results: Loss of finger creases and dominant grip strength: Grip strength in patients with IBM showed mean 20th percentile [IQR 12.27] with loss of finger creases (n=32) versus 31st percentile [IQR 24.42] without loss of finger creases (p=0.008).4
Discussion: Our findings show that loss of distal dorsal interphalangeal finger creases is present in many patients with IBM (40%) compared to controls (15%). Additionally, we show that distal finger creases are associated with reduced grip strength (20th percentile vs 31st percentile; p=0.008). We hypothesize that the presence of reduced distal finger creases is helpful in distinguishing between IBM and ALS, which typically does not present with this finding.
Keywords
Inclusion Body Myositis, Handgrip Strength, Distal Dorsal Finger Creases, Muscle Weakness, Diagnosis
Introduction
Sporadic inclusion body myositis (IBM) is the most common acquired myopathy in populations over age 45.¹,² This disorder causes slowly progressive asymmetric weakness with a predilection for weakness in knee extensors and in finger flexion, particularly in flexor digitorum profundi and flexor pollicis longus in the upper extremities.³–⁵ Though this clinical phenotype of IBM is relatively unique, the diagnosis can be missed without a high index of suspicion, or mistaken for amyotrophic lateral sclerosis (ALS), which can also be an asymmetric progressive motor weakness.⁶ Diagnosis of IBM remains challenging with average delay in diagnosis of 5.6 years after symptom onset.⁷ Weakness in finger flexion has previously been observed to have reduction in dorsal finger creases, which can be a helpful clue to the presence of finger flexor weakness and the diagnosis.⁸,⁹ Expanding on a previous case series⁹, we evaluated a larger population in a cross-sectional cohort study, whose hand strength and function we have previously reported.¹⁰ We propose that a simple visual inspection of the dorsal distal interphalangeal joint crease can aid in identification of IBM and will be associated with reduced grip strength.
Methods
We performed a cross-sectional study of 81 patients with IBM and 74 control patients at a myositis patient conference. Hand grip strength and dominant dorsal hand photographs were obtained in all patients. Patients were classified as control or IBM based on the patient report. Grip strength of the dominant hand was measured twice by Jamar hydraulic hand dynamometer. Grip strength measurements were averaged and normalized by age and sex according to the NIH Toolbox project.¹¹ The loss of dorsal distal interphalangeal creases in photographs of the dominant hand were rated blindly by a board-certified neuromuscular specialist (L.W.) in the sequence that they were acquired. The study was approved by the University of Washington and Washington University institutional review boards.
Results
Our patients with IBM had a male predominance (1.6 male:1 female) that was reversed in the control patient population. The IBM cohort was slightly older with a median age of 68, about four years older than the control cohort. The distal dorsal finger creases were considered abnormal when they were observed to be markedly reduced as shown in the examples in Figure 1. Within the IBM group, a subset had loss of finger creases (40%, n=32), with examples shown in the left column, and are compared to age- and sex-matched controls without loss of dorsal distal finger creases in the right column. In the control group, a smaller subset showed reduced finger creases (15%, n=11). There was no significant difference in age or disease duration between the two IBM sub-groups.
However, the IBM sub-groups did show a difference in grip strength. The median grip strength was lower in the IBM group with loss of dorsal finger creases at the 20th percentile (interquartile range, IQR 12–27) of expected values, compared to the IBM group without reduced finger creases at the 31st percentile [IQR 24–42] (n=49). This difference was statistically significant (p = 0.008; Figure 2). A few of the control patients (n=11) had diminished finger creases, however, there was no significant change in grip strength compared to those without loss of creases. In both control sub-groups, the median grip strength was in the 110–111th percentiles (IQR [100–125] for patients with loss of finger crease and [99–121] for those without).
Figure 2: Loss of finger creases and dominant grip strength: Grip strength in patients with IBM showed mean 20th percentile (IQR 12–27) with loss of finger creases (n=32) versus 31st percentile (IQR 24–42) without loss of finger creases (n=49, p value = 0.008). Control patients with or without loss of distal finger creases both showed normal grip in 110–111th percentile. IQR: interquartile range; IBM: inclusion body myositis
Discussion
Our findings show that loss of dorsal distal interphalangeal finger creases is present in more patients with IBM (40%) than control patients (15%). Additionally, we show that the loss of finger creases within the IBM cohort is associated with reduction of grip strength (20th percentile vs 31st percentile; p = 0.008). We also confirm that grip strength testing is a clinically useful and easy measurement in this population in addition to qualitative testing of distal finger flexor strength. Prior studies have demonstrated that grip strength correlates with finger flexor function, supporting this as a helpful component of the exam.¹²,¹³ It should be noted that testing of the deep finger flexors, while remaining essential in an evaluation for the possibility of IBM, requires proper technique including testing all fingers flexed simultaneously due to the quadriga phenomenon of interconnectedness between deep digit flexors, whereas grip testing is more straightforward for clinicians.¹³
In our IBM cohort, we hypothesize that the worsened grip strength and the loss of dorsal distal finger creases are caused by the same mechanism, which is weakness in the flexor digitorum profundus muscles, and reduced motion at the distal interphalangeal joint. Loss of finger creases has been suspected to be seen as a consequence of weakness at the affected joint, primarily reported in development of flexion
creases and especially in congenital weakness.¹⁴ However, little data is available for loss of finger creases in acquired/degenerative muscle disease, and especially in the dorsal finger creases. Notably, disorders such as ALS which frequently cause distal hand weakness but not finger flexor weakness,¹⁵ do not have this finding in our observations in clinical practice. We expect several factors may be involved in this difference, including the relative sparing of deep finger flexors and the rapidity of symptoms in ALS compared to the slowly progressive weakness often seen in patients with IBM at time of their presentation. The presence of finger creases in 60% of our IBM cohort is suspected to be related to the relative preservation of function in these patients as indicated by the increased grip strength.
The source of absent finger creases in the control cohort is likely different from those with IBM, given the absence of grip weakness. Normal aging expects an increase in distal dorsal finger wrinkles over time.¹⁶ However, reduced mobility even in setting of normal muscle function may occur. Presence of arthritis, primary skin diseases such as scleroderma, or other hereditary sources such as nail-patella syndrome, as well as diabetes (with its association with limited joint mobility) is also associated with reduced wrinkling.¹⁷–¹⁹ These healthy controls should not be easily mistaken for IBM due to lack of motor weakness on exam or by history.
This study has several limitations: Firstly, subjects are self-identified with IBM which raises our possibility of false positives in the IBM group. Secondly, we have only a single observer rating finger creases which raises a question on interobserver validity. The presence of dorsal finger creases in some patients with IBM shows that this test is not highly sensitive. Though finger flexor weakness can help differentiate between those abnormal findings in the control group, they may not be as helpful in setting of other myopathies with finger flexor weakness such as myotonic dystrophies.²⁰
Given the simplicity of examining for this diminishment in dorsal distal finger creases, it can be a helpful complement to a full evaluation for IBM. The presence of reduced distal finger creases is helpful in consideration of potential mimics of IBM such as ALS which more often spares the deep finger flexors and progresses much more quickly so would not be expected to cause this finding.¹⁵,²¹ Additionally, this finding can be a helpful clue to further examine a patient’s grip and finger flexor strength when upper extremity weakness is not apparent on a routine physical exam that may not include finger flexors.
Conclusion
This study provides further confirmation that loss of distal finger creases is associated with IBM and associated with reduced grip strength. This is a helpful feature to identify patients who may have IBM and is best interpreted in combination with an appropriate history and will guide an expanded examination for other clinical features associated with IBM.
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