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B symptoms are unintentional weight loss, fevers and night sweats.

The B Symptoms: What are they?

B symptoms or B-like symptoms are clinical features that signify the hallmark of systemic inflammation. When present, they predict poor patient outcomes. They are unintentional weight loss, fever, and drenching night sweats.

When a patient reports unintentional weight loss of more than 10% in the last six months before any diagnosis; evening fevers of more than 38°C; and drenching nights, we poke into more history to delineate the underlying chronic illness. We emphasize investigating for the presence of cancers – specifically, Lymphoma, for which we occasionally use to stage the disease. We associate these symptoms with advanced disease.

In 1966, relating to the classification of Hodgkin disease, the B symptoms included night sweats, fever, and pruritus. However, the Ann Arbor staging system that replaced the Rye system in 1971 substituted pruritus for unintentional weight loss as the third symptom.

B symptoms are only so if they relate to Lymphoma – otherwise, when they occur in other chronic illnesses such as Tuberculosis, we term them B-like symptoms. A patient likely has TB if, in addition to a productive cough that has lasted for more than two weeks, they report drenching night sweats, weight loss and fevers.

The symptoms correlate with an upstream of inflammatory molecules – C-reactive protein (CRP) and cytokines, especially interleukin-6 (IL-6). There’s presumed cytokine storm that results in more energy consumption and heat dissipation that culminates in weight loss despite the usual feeding patterns, high-grade fevers, and diaphoresis, especially at night.

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It is paramount that we distinguish sweating at night due to hot climatic conditions and drenching night sweats. The latter requires that the patient sweats so much that they attempt changing beddings or their nightclothes. We must ascertain that the high-grade fevers are not due to any known infectious disease – and that, the patient has not intentionally lost weight for whatever reason that may suffice.

As we noted earlier, a couple of chronic inflammatory states give rise to B-like symptoms; it is prudent to restrict the term “B symptoms” to the staging of lymphomas. However, any presence of such symptoms must prompt thorough investigations to delineate the underlying disease. It is so because they determine the aggressiveness of the disease in question, especially Hodgkin and Non-Hodgkin lymphomas.

In a nutshell, B symptoms are constitutional clinical features. They are not only associated with advanced disease but also predict poor patient outcomes. We attribute the poor prognosis to both reduced efficacy of the drug regimens in use and an increased propensity for drug toxicities. B symptoms are only so with lymphomas – otherwise, we term them constitutional symptoms to prevent ambiguity in clinical practice. We do not solely use them to make a diagnosis because they are unspecific.


MBChB (MUK), Graduate Fellow, Department of Physiology, Makerere University Founder and Content Creator Peer reviewer, Associate Editor

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