Chronic Infection or Inflammatory Condition: The patient's symptoms of low-grade fever at night and fatigue, combined with slightly elevated globulin levels and a normal CRP and sed rate, suggest a chronic infection or inflammatory condition. The lack of significant abnormalities in the CBC and other lab tests makes an acute infection or severe inflammatory condition less likely.

Anemia of Chronic Disease: Although the patient's hemoglobin and hematocrit are within normal limits, the slightly elevated RDW and low MCHC could suggest a mild anemia. The presence of fatigue and low-grade fever supports this diagnosis.
Thyroid Disorder: Despite a normal TSH, thyroid disorders can sometimes present with fatigue and low-grade fever. Further evaluation of thyroid function might be necessary.
Viral Infection: The patient's symptoms could be consistent with a viral infection, such as a mild case of mononucleosis or another viral syndrome, although the lack of significant lymphocytosis makes this less likely.

Lymphoma or Leukemia: Although the CBC does not show significant abnormalities, a diagnosis of lymphoma or leukemia should always be considered in patients with unexplained fever and fatigue. These conditions can present subtly and require further evaluation, including lymph node biopsy or bone marrow examination if suspected.
Tuberculosis (TB): TB can present with low-grade fever, fatigue, and night sweats. The fact that the patient's symptoms are worse at night increases the suspicion for TB, and a purified protein derivative (PPD) test or interferon-gamma release assay (IGRA) should be considered.
Endocarditis: Infective endocarditis can cause low-grade fever, fatigue, and embolic phenomena. Although the patient does not have the typical heart murmur or embolic events, this diagnosis should be considered, especially if the patient has a history of valvular heart disease.

Autoimmune Disorders (e.g., Lupus, Rheumatoid Arthritis): These conditions can present with a wide range of symptoms, including low-grade fever and fatigue. However, the lack of specific autoantibodies or significant inflammatory markers makes these diagnoses less likely.
Parasitic Infections: Certain parasitic infections, such as toxoplasmosis or malaria, can cause prolonged fever and fatigue. These diagnoses are less likely without a history of travel or exposure but should be considered if other diagnoses are ruled out.
Castleman Disease: This rare condition can cause fever, fatigue, and lymphadenopathy. It is often associated with lymphoma or autoimmune disorders and would require further evaluation, including lymph node biopsy, for diagnosis.