Weakness at the connections between muscles and joints may affect bones and could contribute to the chronic fatigue felt by people with Gaucher disease (GD), a study found.
Tendon stiffness could be “a sign of alarm,” its researchers said of this study into patients’ Achilles tendons, as it might signal “mechanical overload” on bones. As such, assessing tendon’s elasticity in GD patients could provide information relevant to chronic fatigue, a common yet often hard to treat symptom in these people, the team suggested.
The study “Muscle-tendon weakness contributes to chronic fatigue syndrome in Gaucher’s disease” was published in the Journal of Orthopaedic Surgery and Research.
Chronic fatigue is the most frequent symptom when Gaucher is diagnosed. While enzymatic replacement therapy (ERT) is effective to ease disease manifestations such as spleen and liver enlargement and skeletal problems, fatigue often does not go away, with almost one-quarter of patients still experiencing it after years of therapy.
Chronic fatigue in Gaucher is usually attributed to overactive metabolism, muscle disease, or an increase in blood levels of cytokines, immune system messenger molecules.
However, several other factors could also be involved, such as low red blood cell counts (anemia), pain, depression, anxiety, poor sleep, emotional distress, or medication side effects.
Bone disease, which affects most GD patients, and such disabling bone complications as osteoporosis (brittle bones more prone to fractures), deformation, and osteonecrosis — the break down and death of bone tissue — also can be a source of fatigue.
Investigators at the Fundación Española Estudio y Tratamiento de la Enfermedad de Gaucher y Otras Lisosomales (FEETEG), in Spain, further explored factors that might underlie fatigue in GD.
Specifically, they wondered if weakness at the junctions between muscles and tendons could be an important contributor to fatigue.
The team measured the properties of the Achilles tendon — the most powerful and thick tendon of the body, connecting muscles in the back of the calf to the heel bone — in people with GD.
Researchers used strain-elastography (S-ELA) to measure the structure and elasticity of the Achilles’ tendon in 27 adults with GD, ages 18 to 62 (mean age, 41), who had chronic fatigue. Twenty-five had type 1 and two had type 3 disease. All were on ERTs, which they had been taking for a mean of 13 years.
S-ELA is a non-invasive way to measure tissue properties in real-time by ultrasound. It applies minimal compression and captures how the tissue reacts. Based on the principle that a stiff region experiences less strain (deformation) than surrounding softer tissue under an equal amount of stress, it allows the identification of tissue regions with an altered elasticity.
Testing of the Achilles myotendinous junction — at the interface between muscle and tendon — found a normal tendon structure in all patients. But an abnormal stiffness was detected in 17 (62.9%) patients. In 11 of these people (40.7%), this increased stiffness or hardness affected Achilles’ tendons in both legs.
A greater degree of tendon hardness was associated with a lower health-related quality of life, as reported by patients.
In contrast, no relationship was seen between tendon stiffness and bone weakness or severity of bone disease, patients’ genetic profile, whether their spleen had been removed, time on therapy, or the presence of other diseases.
“A possible interpretation of the findings obtained in this study suggests that mechanical overload on lower limbs is the cause of tendon dysfunction,” the researchers wrote.
“We propose that exploring tendon elasticity produces useful information in the evaluation of chronic fatigue presented by patients with GD,” they added.
One way to do it, the team said, is by using S-ELA, which they called “a low-cost, sensitive, painless, and fast method to detect tissue alterations.”
“The identification of subclinical tendon alteration would be a sign of alarm, focused on the risk of development of bone complications,” the scientists also wrote.
They further mentioned a project focused on physical activity in people with GD, which aims to increase functional strength of the lower limbs to enable greater stability and power, and to both provide improvements in physical activities and less fatigue.