Understanding Diffuse Infiltrative Lymphocytosis Syndrome (DILS)

Diffuse Infiltrative Lymphocytosis Syndrome (DILS) is a rare condition that occurs in some people living with HIV ^[1]. While the name is long and technical, it essentially describes a specific way your immune system behaves in the presence of the HIV virus ^[2].

Because DILS involves swelling and inflammation, it can be worrying when you first hear about it. However, it is important to know that DILS is not cancer; it is an inflammatory response thought to involve chronic immune activation ^[1][3]. ART is essential for HIV and often improves DILS, though gland enlargement or sicca symptoms may persist ^[2].

What is Happening Inside the Body?

The immune system uses different types of white blood cells to fight infections. One group, called CD8+ T-cells, is responsible for attacking viruses. In DILS, these cells become overly active and begin to multiply and travel into various organs instead of just staying in the bloodstream ^[1][3].

We call this process infiltration. When these cells “infiltrate” or crowd into a tissue, they cause that organ to swell and stop working correctly ^[1]. This most commonly happens in the salivary glands (the glands in your jaw and neck that make spit), but it can also affect the lungs, kidneys, or liver ^[1][4].

Common Signs and Symptoms

DILS often looks like other conditions, such as Sjögren syndrome (an autoimmune disease that causes dryness) ^[3]. However, in DILS, the underlying cause is the immune system’s reaction to HIV ^[1].

The most frequent signs include:

• Swollen Glands: Persistent, painless swelling of the salivary glands on both sides of the face or neck ^[1][4].
• Sicca Symptoms: A medical term for “dryness,” specifically xerostomia (dry mouth) and dry eyes ^[1][4].
• Swollen Lymph Nodes: Generalized swelling of the lymph nodes throughout the body ^[1].
• Organ-Specific Issues: If the lungs are involved, you may have a dry cough or shortness of breath (sometimes called lymphocytic interstitial pneumonia) ^[1][4].

Who Gets DILS?

DILS is rare. One large Taiwanese cohort study found it in about 0.28% of people living with HIV ^[5]. It is most commonly seen in people who are not yet on Antiretroviral Therapy (ART) or those whose HIV is not currently suppressed (meaning the “viral load” in the blood is high) ^[2][5].

It is a common misconception that DILS only happens when someone has a very low CD4 count (the “helper” cells often used to track HIV health). In reality, DILS can occur even if your CD4 count is normal or high ^[1]. Historically, doctors have looked at persistent absolute CD8+ lymphocytosis assessed over time; the CD4:CD8 ratio is nonspecific and is not a stand-alone diagnostic or treatment-response measure ^[1].

How DILS is Managed

The primary goal of treating DILS is to manage the HIV virus. When the virus is suppressed, the chronic immune activation can be calmed ^[2].

• Antiretroviral Therapy (ART): This is the foundation of treatment. For many patients, starting or optimizing ART is enough to make the swelling and dryness improve ^[1][2]. However, established tissue damage may not reverse, and responses are variable.
• Corticosteroids: If the inflammation is severe or affecting vital organs like the lungs or kidneys, doctors may temporarily prescribe steroids (like prednisone) to bring the swelling down quickly ^[1][6]. However, these are used cautiously because they can further weaken the immune system ^[2].
• Symptom Relief: While waiting for ART to work, your doctor may suggest sugar-free gum, saliva substitutes, or eye drops to help with the dryness ^[4].

With consistent HIV treatment, the prognosis for DILS is often good, and the symptoms often improve over several months, though some responses are incomplete ^[1][2].