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The joint effort: MSK quiz
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Received: ,
Accepted: ,
How to cite this article: Thippeswamy PB, Premnazeer SF, Bhardwaj P. The joint effort: MSK quiz. Indian J Musculoskelet Radiol. 2026;8:124-6. doi: 10.25259/IJMSR_19_2026
PART 1: QUESTIONS
A 37-year-old male from South India presented with complaints of painful non-progressive swelling in the dorsal aspect of the mid-forearm for 2 months. There was no history of fever, trauma, or previous surgery. On palpation, there was a firm swelling without any redness or change in local temperature. He was referred to the radiology department for an ultrasound (USG) evaluation.
Figures 1 and 2 show pre-treatment USG of the forearm, which showed a well-defined solid hypoechoic lesion, with a linear tubular hyperechoic structure in the center. Figures 3 and 4 show post-treatment USG of the forearm, which showed a minimally liquefied lesion, with a fragmented appearance of a linear tubular hyperechoic structure in the center.
- Pretreatment USG image of the forearm lesion. USG: Ultrasound sonography
- Pretreatment USG image of the forearm lesion. USG: Ultrasound sonography
- Post treatment USG image of the forearm lesion. USG: Ultrasound sonography
- Post treatment USG image of the forearm lesion. USG: Ultrasound sonography
What is the diagnosis?
Was the treatment sufficient in this case?
What are the complications?
PART 2: ANSWERS
Intramuscular dirofilariasis
Although the parasite was dead and fragmented following medical therapy, the surrounding inflammatory granulation tissue persisted, leading to continued pain during exertion. Therefore, medical treatment alone is inadequate, and surgical excision is recommended for definitive management
The infected muscle nodule can develop secondary bacterial infections, or they mimic a malignant nodule or metastasis. Other complications include sensory or motor symptoms, secondary to nerve compression by the lesion.
Diagnosis
1. Intramuscular dirofilariasis.
Findings
USG showed a small well-defined solid hypoechoic lesion in the intramuscular plane of the extensor carpi radialis longus muscle, adjacent to the myotendinous junction in the mid-forearm level. An internal tubular serpiginous structure, with parallel echogenic walls and an anechoic center, is seen within the lesion. The serpentine structure shows active movements within the lesion.
DISCUSSION
Dirofilariasis is a zoonotic infection primarily caused by Dirofilaria repens, with dogs and other canines as the main reservoirs.[1] Humans become accidental hosts through mosquito bites (e.g., Aedes, Anopheles, and Culex), which transmit larvae during a blood meal. The infection often affects the lungs or eyes but can also cause subcutaneous nodules, usually on the face, limbs, or genital area. These nodules[2] may compress nerves,[3] leading to sensory and motor issues. For example, nodules in the masseter muscle can cause difficulty chewing, whereas those in the temporalis muscle may result in headaches and jaw stiffness (trismus).[4]
Dirofilaria immitis can cause pulmonary coin lesions. Treatment is usually surgical excision of the lesion, but for multiple lesions, ivermectin or diethylcarbamazine may be used.
A key differential is myocysticercosis, which presents as small hypoechoic cysts, sometimes with a visible scolex, and may develop calcification over time. Unlike dirofilariasis, it does not show coiled, linear structures.[5]
Acknowledgment:
We thank Dr. S. Rajasapabathy for his immense support.
Ethical approval:
Institutional Review Board approval is not required.
Declaration of patient consent:
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given consent for clinical information to be reported in the journal. The patient understand that the patient’s names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Conflicts of interest:
There are no conflicts of interest.
Use of artificial intelligence (AI)-assisted technology for manuscript preparation:
The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.
Financial support and sponsorship: Nil.
References
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