Illustration of glowing joints representing early detection of inflammation.

Unexplained Joint Pain and Fever? How Advanced Scans Can Spot Hidden Inflammation

Avery Sinclair in Health & Wellness December 2025 • 4 min read.

"When standard tests miss the signs, innovative imaging techniques like FDG-PET/CT offer a new window into diagnosing conditions like Henoch-Schönlein vasculitis."

For many, the aches and pains of everyday life are fleeting and easily dismissed. But what happens when joint pain becomes persistent, unexplained, and accompanied by a fever? This was the concerning reality for a young boy whose case highlights the complexities of diagnosing certain conditions, especially when they present in atypical ways. While arthritis is commonly associated with joint issues, sometimes the underlying cause is more elusive, requiring a deeper dive into the body's inflammatory processes.

Henoch-Schönlein vasculitis (HSP) is a systemic vasculitis that primarily affects children. Although joint pain or arthritis is a common feature, occurring in about 80% of cases, this young patient's experience defied the norm. Standard examinations failed to reveal the telltale signs of arthritis, leaving doctors searching for answers. This is where a sophisticated imaging technique known as fludeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT) stepped in to shed light on the situation.

The case underscores the value of advanced imaging in uncovering hidden inflammation when clinical assessments fall short. It prompts us to consider the possibilities when conventional diagnostic methods don't provide a clear picture, and how technology can bridge the gap to improve patient outcomes.

FDG-PET/CT: A Window into Hidden Inflammation

Illustration of glowing joints representing early detection of inflammation.

FDG-PET/CT is a powerful imaging tool that combines the strengths of two modalities: PET and CT. PET scans use a radioactive tracer (fludeoxyglucose, or FDG, in this case) to detect areas of high metabolic activity in the body. Because inflammatory cells and malignant cells tend to have increased glucose metabolism, they light up on the scan, indicating areas of concern. The CT scan provides detailed anatomical information, allowing doctors to pinpoint the exact location of the activity.

In the case of the young boy, the FDG-PET/CT scan revealed increased FDG uptake in multiple large joints and tendons. This suggested active polyarthritis (inflammation of multiple joints) and polytendinitis (inflammation of multiple tendons). Despite the scan's findings, physical and ultrasound evaluations failed to detect any signs of arthritis. This discrepancy was key to understanding the underlying issue: the inflammation was present but not yet clinically apparent.

Early Detection: FDG-PET/CT may detect inflammatory activity before it's visible through standard examinations.
Comprehensive View: It visualizes inflammation throughout the body, not just in specific areas.
Diagnostic Clarity: It helps differentiate between inflammatory and non-inflammatory conditions.

The information provided by the FDG-PET/CT scan ultimately led to the diagnosis of Henoch-Schönlein vasculitis, despite the absence of typical clinical signs of arthritis. This highlights the potential of FDG-PET/CT to identify inflammatory activity in painful joints that might otherwise go undetected, especially in cases with atypical presentations or when standard evaluations are inconclusive.

Hope for Early Diagnosis

Advanced imaging techniques like FDG-PET/CT offer hope for earlier and more accurate diagnoses of complex conditions. By visualizing hidden inflammation, these tools can guide treatment decisions and improve outcomes for patients with unexplained joint pain, fever, and other elusive symptoms. Further research will help define the full potential of FDG-PET/CT in Henoch-Schönlein vasculitis and other inflammatory disorders, paving the way for more personalized and effective care.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1186/s13256-016-0913-8, Alternate LINK

Title: Fludeoxyglucose Positron Emission Tomography-Computed Tomography Scan Showing Polyarthritis In A Patient With An Atypical Presentation Of Henoch-Schönlein Vasculitis Without Clinical Signs Of Arthritis: A Case Report

Subject: General Medicine

Journal: Journal of Medical Case Reports

Publisher: Springer Science and Business Media LLC

Authors: Christiaan F. Mooij, Rick Hermsen, Esther P. A. H. Hoppenreijs, Chantal P. Bleeker-Rovers, Marloes M. Ijland, Lioe-Fee De Geus-Oei

Published: 2016-06-02

Everything You Need To Know

What is FDG-PET/CT, and how does it help in diagnosing unexplained joint pain and fever?

FDG-PET/CT is an advanced imaging technique combining Positron Emission Tomography (PET) and Computed Tomography (CT). The PET component uses fludeoxyglucose (FDG), a radioactive tracer, to identify areas with high metabolic activity, such as inflammation or malignant cells. The CT component provides detailed anatomical information to pinpoint the precise location of this activity. This combination allows doctors to visualize hidden inflammation that might be missed by standard examinations, leading to more accurate diagnoses in cases of unexplained joint pain and fever.

In what specific scenarios might FDG-PET/CT be more useful than standard examinations for diagnosing joint pain?

FDG-PET/CT can be particularly useful when standard examinations, like physical exams and ultrasound, fail to reveal the cause of joint pain. This is especially true in cases with atypical presentations or when clinical assessments are inconclusive. For instance, it can detect inflammatory activity before it becomes clinically apparent, offering a comprehensive view of inflammation throughout the body, helping differentiate between inflammatory and non-inflammatory conditions that standard testing misses.

How did FDG-PET/CT contribute to the diagnosis of Henoch-Schönlein vasculitis in the young boy mentioned, and what makes this case significant?

In the described case, the young boy presented with joint pain and fever, but standard examinations didn't reveal typical signs of arthritis, a common feature of Henoch-Schönlein vasculitis (HSP). The FDG-PET/CT scan revealed increased FDG uptake in multiple large joints and tendons, indicating active polyarthritis and polytendinitis, which suggested inflammation. Although physical and ultrasound evaluations failed to detect any signs of arthritis, the scan's findings led to the diagnosis of Henoch-Schönlein vasculitis. This case is significant because it underscores how FDG-PET/CT can uncover hidden inflammation and lead to a diagnosis even in the absence of typical clinical signs.

What are the potential benefits of using FDG-PET/CT for the early detection of conditions like Henoch-Schönlein vasculitis?

Early detection of conditions like Henoch-Schönlein vasculitis (HSP) through FDG-PET/CT allows for more timely and appropriate treatment. This can lead to improved patient outcomes and potentially prevent disease progression and complications. FDG-PET/CT can identify inflammatory activity before it's visible through standard examinations, offering a more comprehensive view of inflammation throughout the body and helping to differentiate between inflammatory and non-inflammatory conditions.

What is the significance of detecting polytendinitis using FDG-PET/CT, and how does it relate to conditions like Henoch-Schönlein vasculitis?

Detecting polytendinitis (inflammation of multiple tendons) using FDG-PET/CT is significant because it can indicate underlying inflammatory processes that might not be apparent through standard clinical assessments. In the context of conditions like Henoch-Schönlein vasculitis (HSP), which primarily affects children and is characterized by systemic vasculitis, polytendinitis can be an important clue, especially when typical signs of arthritis are absent. The ability of FDG-PET/CT to visualize inflammation in tendons, as well as joints, provides a more complete picture of the inflammatory activity, aiding in diagnosis and treatment planning.