Differential Diagnosis

The patient presents with 2 weeks of fever, low calcium, high ESR and CRP, and normal CBC, CMP, CEA, AFP, and ANA. Based on these findings, the differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis

  • Sarcoidosis: This condition can cause fever, elevated inflammatory markers (ESR and CRP), and low calcium levels due to vitamin D deficiency or increased calcium deposition in granulomas. The normal CBC, CMP, and negative ANA also support this diagnosis, as sarcoidosis can present with non-specific systemic symptoms.

• Other Likely Diagnoses

  • Tuberculosis (TB): TB can cause prolonged fever, elevated ESR and CRP, and low calcium levels. Although the CBC and CMP are normal, TB can have a varied presentation, and the absence of specific markers like ANA does not rule it out.
  • Lymphoma: Some types of lymphoma can present with systemic symptoms like fever, night sweats, and weight loss, along with elevated inflammatory markers. Low calcium levels could be due to bone involvement or paraneoplastic syndromes.
  • Chronic Inflammatory Diseases (e.g., Crohn's disease, ulcerative colitis): These conditions can cause chronic inflammation, leading to elevated ESR and CRP, and may also result in low calcium levels due to malabsorption or vitamin D deficiency.

• Do Not Miss Diagnoses

  • Malignancy (e.g., multiple myeloma, metastatic cancer): Although the CEA and AFP are normal, and the CBC is unremarkable, certain malignancies can present with non-specific symptoms like fever and elevated inflammatory markers. Multiple myeloma, in particular, can cause low calcium levels due to bone destruction.
  • Endocarditis: Infective endocarditis can cause prolonged fever, elevated ESR and CRP, and may lead to embolic phenomena or cardiac complications if not promptly diagnosed and treated.
  • Vasculitis (e.g., giant cell arteritis, Takayasu arteritis): These conditions can present with systemic symptoms, elevated inflammatory markers, and may cause low calcium levels due to inflammation or malabsorption.

• Rare Diagnoses

  • Familial Mediterranean Fever: A genetic disorder characterized by recurrent episodes of fever, often accompanied by elevated inflammatory markers and may involve low calcium levels due to secondary hyperparathyroidism.
  • Hyperparathyroidism: Although less common, primary hyperparathyroidism can cause low calcium levels (due to secondary hyperparathyroidism) and may be associated with elevated inflammatory markers.
  • Osteomalacia: A condition characterized by softening of the bones due to vitamin D deficiency, which can cause low calcium levels and may be associated with elevated inflammatory markers.