Rosai-Dorfman disease is a rare condition in which a type of immune cell called a histiocyte multiplies abnormally and accumulates in the lymph nodes, causing them to swell dramatically. The hallmark sign is painless, often massive swelling on both sides of the neck, though the disease can appear in other parts of the body as well. Most diagnoses occur around age 20, and the condition is slightly more common in males.
What Happens in the Body
Histiocytes are white blood cells that normally help clean up damaged tissue and fight infection. In Rosai-Dorfman disease, these cells proliferate far beyond what the body needs and pile up inside the lymph nodes. The buildup stretches the nodes to an unusual size, which is why the swelling can look so striking compared to what you might see with a common infection.
Under a microscope, these overgrown histiocytes display a distinctive behavior: they engulf other immune cells, mostly small lymphocytes, and hold them intact inside their own cell body. Pathologists call this emperipolesis. A single histiocyte may contain anywhere from one to eight lymphocytes, each surrounded by a visible clear halo. This feature is considered the hallmark of the disease and is one of the key findings that separates it from other conditions involving histiocyte overgrowth.
Common Symptoms
The most noticeable symptom is painless, swollen lumps on both sides of the neck. The swelling can become quite large and may persist for weeks or months. Beyond the neck, histiocyte buildup can affect lymph nodes in the armpits, groin, and the center of the chest.
Some people experience no other symptoms at all. Others develop fever, fatigue, night sweats, pale skin, a persistent runny nose, or unexplained weight loss. These systemic symptoms can overlap with many other conditions, which is one reason the disease sometimes takes time to diagnose.
Extranodal Disease
In some cases, the disease appears outside the lymph nodes entirely. It can involve the skin, nasal cavity, salivary glands, bone, and other areas of the head and neck. Central nervous system involvement is uncommon, especially without lymph node disease elsewhere, but it does occur. In a series of 11 patients with brain or spinal cord involvement, symptoms included headaches, seizures, numbness, and in one case, paralysis. Most of these lesions were attached to the membrane surrounding the brain rather than growing within the brain tissue itself.
What Causes It
The exact cause remains unclear, but genetic research has uncovered important clues. About one-third of cases carry mutations in genes that activate a specific cell-growth signaling pathway. A study analyzing 21 cases found mutations in either the KRAS or MAP2K1 gene in 33% of patients, and these mutations were mutually exclusive, meaning a given case had one or the other but never both. No mutations were found in several other genes that are commonly altered in related conditions. This suggests that at least a subset of cases are driven by a clonal process, where a single abnormal cell multiplies out of control, rather than being a purely reactive or inflammatory condition.
How It Is Diagnosed
Diagnosis requires a biopsy of an affected lymph node or tissue mass. Pathologists look for the characteristic large histiocytes with emperipolesis described above. They also use special staining techniques to confirm the identity of the cells. In Rosai-Dorfman disease, the histiocytes stain positive for two markers (S100 and CD68) and negative for CD1a. That last detail is critical because Langerhans cell histiocytosis, a different disease that can look similar, stains positive for CD1a. This staining pattern is what allows pathologists to distinguish between the two conditions with confidence.
Treatment Options
Many cases of Rosai-Dorfman disease are managed with observation alone, particularly when the swelling is the only issue and isn’t compressing vital structures. The disease can wax and wane on its own, and some patients see their symptoms improve without any intervention. When treatment is needed, options include surgical removal of the affected tissue and corticosteroids to reduce inflammation.
For patients with disease that keeps coming back or spreads to multiple sites, newer targeted therapies are showing promise. Because a significant portion of cases involve mutations in the KRAS or MAP2K1 genes, drugs that block the signaling pathway these genes activate have been tested. A study of 16 patients treated with cobimetinib, a drug that inhibits this pathway, found that patients whose tumors carried one of these mutations had an overall response rate of 88%, with 71% achieving a complete response. Patients without the mutations responded at a lower rate of 38%, and none had a complete response. After one year, every patient with a mutation remained free of disease progression, compared to just 29% of those without.
Side effects from these drugs were common regardless of mutation status, so close monitoring during treatment is important. Some patients responded well even at lower doses, which may help manage side effects while still controlling the disease.
Long-Term Outlook
Rosai-Dorfman disease is generally considered benign, and fatal outcomes are rare. However, recurrence is common. In a review of 126 reported cases involving the nasal and sinus area, just over 25% of patients had no recurrence, while nearly 55% experienced a recurrent, persistent, or progressive course. About 5% of patients died from the disease. These numbers come from sinonasal cases specifically, which tend to be more treatment-resistant than typical nodal disease, but they illustrate that ongoing monitoring matters even after initial treatment.
For the majority of people, the disease follows a chronic but manageable pattern. Flares of swelling may come and go over months or years, and treatment decisions are often guided by whether the disease is causing symptoms or threatening organ function rather than by the mere presence of enlarged lymph nodes.