Quadriceps femoris muscle ultrasound in sarcoidosis: an observational case-control study.

Background: Although loss of muscle mass may be associated with general weakness, intolerance to physical activity and fatigue, it is underestimated and poorly understood in patients with sarcoidosis.

Aim: To compare the quadriceps femoris muscle (QFM) thickness measured by ultrasonography (US) between the female patients with sarcoidosis and controls, secondly to assess the correlation between the muscle strength, fatigue and QFM thickness.

Design: Observational, case-control study.

Setting: Physical Medicine and Rehabilitation Department of a University Hospital.

Population: Thirty-one women with sarcoidosis and 27 healthy volunteers were included in the study.

Methods: The participants were evaluated for the following outcomes: 1) handgrip strength; 2) QFM thickness measured using US; and 3) sonographic thigh adjustment ratio (STAR). The sarcoidosis group was also evaluated with the 30-second chair stand test (30s-CST) and Fatigue Severity Scale (FSS).

Results: The QFM thickness and STAR values of the patients with sarcoidosis were significantly lower than those of the controls (P=0.0001). However, no statistically significant difference was observed between the handgrip strengths of the groups (P=0.581). There was no statistically significant correlation between the STAR values and handgrip strength in the sarcoidosis group; however, there was a significant positive correlation between the STAR values and 30s-CST (r=0.467, P=0.008).

Conclusions: Loss of muscle mass is one of the musculoskeletal conditions in patients with sarcoidosis that may be associated with nonspecific symptoms, such as general debility, intolerance to physical activity, and fatigue. In the present study, no difference was observed in hand grip strength between the groups, while we found that QFM thickness was affected in patients with sarcoidosis when compared to the controls. The ultrasonographic QFM evaluation seems to be an innovative tool which may be used at all stages of sarcoidosis patient follow-up.

Clinical rehabilitation impact: The grip strength is a commonly used test to detect muscle weakness, but onset of a decrease in muscle mass in the lower extremities may occur earlier. Considering the increased burden of musculoskeletal problems in this population, performing 30s-CST and sonographic QFM thickness is practical methods to identify risky patients.