Which of the following symptoms is most characteristic of acute lymphoblastic leukemia?

Acute lymphoblastic leukemia (ALL) is a type of cancer that affects the blood and bone marrow and is characterized by the overproduction of immature lymphocytes. One of the hallmark symptoms associated with ALL is diffuse lymphadenopathy, which refers to the enlargement of lymph nodes throughout the body.

In this context, diffuse lymphadenopathy occurs due to the accumulation of leukemic cells within the lymphatic system, leading to the enlargement of lymph nodes. This symptom is significant because it can indicate the disease's involvement beyond just the bone marrow and signifies a systemic response to the underlying pathology.

The other symptoms listed can occur in various conditions but are not as characteristic or definitive for ALL. Mild ankle pain could result from many causes unrelated to leukemias, such as musculoskeletal issues or injuries. Chronic fatigue is a common, nonspecific symptom associated with many illnesses and cannot pinpoint ALL. A skin rash may accompany certain medical conditions or reactions but is not a primary or characteristic symptom of acute lymphoblastic leukemia.

Thus, diffuse lymphadenopathy stands out as a key indicator of ALL, highlighting its critical role in diagnosis and understanding the disease's clinical presentation.