A 33-year-old Caucasian female patient with a 10-year history of Crohn’s disease, presented with a flare up of disease and a 3-month history of increasing calf myalgia and progressive walking difficulty. Examination revealed swelling of both calves, with localised tenderness.
Biochemical blood tests, including creatine kinase were within normal limits.
MR imaging of both legs was performed. Axial short tau inversion recovery (STIR) sequences identified high signal in keeping with diffuse oedema within the muscles of the superficial-posterior compartment, more profound at the right gastrocnemius muscle. The underlying bones were not affected (Fig. 1).
A subsequent MR scan of the small bowel including fat-suppressed post-contrast T1-weighted showed a short segment of abnormally enhancing thickened small bowel in keeping with an acute flare up of Crohn’s disease.
A diagnosis of Crohn’s induced acute gastrocnemius muscle syndrome was therefore made [9].
The patient was commenced on prednisolone but showed no improvement. She was then commenced on an infliximab regime.
Upon review few weeks after, symptoms had improved. Subsequently, the patient had a follow up MRI scan which revealed complete resolution of the signal change within the muscles of both legs (Fig. 2).
Crohn’s Disease (CD) is a chronic granulomatous inflammatory disease of the gastrointestinal tract with a tendency towards relapse and remission [1]. The prevalence of extra-intestinal manifestations in patients with inflammatory bowel disease ranges from 25-40% [2]. Involvement of the musculoskeletal system is common and manifests in the form of pauci-, polyarthritis, myositis and myalgia, generally classified under the broad spectrum of spondyloarthropathies. Myositis can affect most muscle groups, including the extra-ocular muscles. Focal gastrocnemius myositis is rare manifestation that has been reported 9 times in the literature (3-11). This entity has been referred to a gastrocnemius myalgia syndrome in published literature thus far [9]. To our knowledge this is the second such case from the United Kingdom and the first from Wales. Like the previously reported cases, creatine kinase was normal. Diagnosis was made with MR and treatment with prednisolone and infliximab. Although ultrasound would demonstrate muscle enlargement and oedema, we felt contrast enhanced MR was ideal in demonstrating the affected region of muscle. In this case, the diagnosis was made easier with the presence of a Crohn’s flare up demonstrated on small bowel MR. If gastrocnemius myositis was seen in isolation, the differential diagnosis would include infectious myositis, infiltrating neoplasm, e.g. muscle lymphoma, myositis associated with connective tissue diseases such as, SLE, scleroderma and Sjögren's syndrome, although clinical correlation is recommended. In a patient with known IBD, especially Crohn’s, even in the absence of a flare up, gastrocnemius myalgia syndrome should be considered as the myositis can precede the bowel flare up. We did not proceed to biopsy in this case but biopsies have been performed in many of the published studies so far (Table 1). As previous cases have shown, symptoms can be refractory and high dose steroid along with cytotoxic agents may be needed for a sustained response (Table 1). To our knowledge this was the first instance in the published literature so far of infliximab being used for treatment.
Gastrocnemius muscle syndrome
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Based on the provided lower limb MRI images, symmetrical thickening and abnormal signals in both gastrocnemius muscles (especially the medial and lateral heads) can be observed, with edema and inflammatory changes more pronounced on T2-weighted or enhanced sequences. There are no prominent lesions in other muscle groups or the skeletal system, and no evidence of bone structural damage or significant joint abnormalities. Overall, the findings suggest localized muscle inflammation.
The differential diagnoses above are primarily based on imaging findings and the patient’s medical history, in conjunction with laboratory data and clinical symptoms.
Taking into account the patient’s 10-year history of Crohn’s disease, the current active disease status, bilateral symmetrical gastrocnemius inflammatory changes, and normal serum CK levels, the most likely diagnosis is:
Crohn’s Disease-Associated Gastrocnemius Myositis (also known as “gastrocnemius myalgia syndrome”).
If diagnostic uncertainty persists, a biopsy may be considered to exclude other rare pathologies. However, the clinical and imaging findings strongly support Crohn’s-related gastrocnemius myositis.
Treatment Strategy:
Rehabilitation and Exercise Prescription (FITT-VP Principle):
Safety Precautions: If there is significant pain or increased swelling, seek medical attention promptly to adjust the treatment plan. Long-term corticosteroid use requires vigilance for osteoporosis, and exercise intensity should be personalized. Regular follow-up is essential to monitor changes in both intestinal and muscular symptoms.
Disclaimer: This report is based on available information for reference only and cannot replace an in-person consultation or professional medical advice. If you have any questions or changes in your condition, please consult a qualified medical institution promptly.
Gastrocnemius muscle syndrome
