Differential Diagnosis for 56-year-old Patient with Hip and Buttock Pain

The patient presents with hip pain and pain in the buttock, alongside abnormal blood results indicating a low white cell count (WCC 3.0), low neutrophils (1.6), and low lymphocytes (0.9). Given these symptoms and lab results, the following differential diagnoses are considered:

• Single Most Likely Diagnosis

  • Viral infection or bone marrow suppression: The low WCC, particularly the low neutrophil and lymphocyte counts, could suggest a viral infection affecting the bone marrow or another form of bone marrow suppression. This could be due to various causes, including medications or underlying diseases affecting the bone marrow.

• Other Likely Diagnoses

  • Autoimmune disorders: Conditions like rheumatoid arthritis or lupus can cause joint pain and also affect blood cell counts, though the pattern of cytopenias can vary.
  • Chronic diseases: Chronic diseases such as kidney disease or liver disease can lead to abnormalities in blood cell counts and may cause or contribute to the patient's pain symptoms.
  • Medication side effects: Certain medications can suppress the bone marrow, leading to low blood cell counts. The patient's medication history should be reviewed.

• Do Not Miss Diagnoses

  • HIV infection: Although the patient does not show infection symptoms, HIV can cause a decrease in WCC, particularly in the early stages or in those who are not yet symptomatic. It's crucial to consider HIV due to its significant implications for treatment and prognosis.
  • Leukemia or lymphoma: These conditions can cause abnormalities in blood cell counts and may present with nonspecific symptoms such as pain. Early detection is critical for effective management.
  • Aplastic anemia: A condition where the bone marrow fails to produce blood cells, which can be life-threatening if not addressed promptly.

• Rare Diagnoses

  • Parvovirus B19 infection: This virus can cause a temporary shutdown of bone marrow production, leading to cytopenias, though it's more commonly associated with anemia.
  • Felty's syndrome: A rare complication of long-standing rheumatoid arthritis characterized by rheumatoid arthritis, splenomegaly, and neutropenia.
  • Pure white cell aplasia: A rare condition where there is a selective decrease in the production of white blood cells, which could present with similar lab findings.

Given the patient's presentation and lab results, it's essential to conduct a thorough history and physical examination, review current medications, and consider further diagnostic testing (such as bone marrow biopsy, viral serologies, and autoimmune panels) to determine the underlying cause of the patient's symptoms and abnormal blood counts.