Differential Diagnosis for CK Elevation, LN Swelling in Neck, and Abdominal Pain

Single Most Likely Diagnosis

• Polymyositis or Dermatomyositis: These are inflammatory muscle diseases that can cause elevated creatine kinase (CK) levels due to muscle damage. The lymph node (LN) swelling in the neck could be related to an underlying autoimmune or inflammatory process, and abdominal pain might be secondary to muscle involvement or other associated conditions.

Other Likely Diagnoses

• Lymphoma: Both Hodgkin's and non-Hodgkin's lymphoma can present with lymphadenopathy (LN swelling), and some cases may have elevated CK levels if there is muscle involvement. Abdominal pain could be due to lymph node enlargement or other complications.
• Sarcoidosis: This is a systemic granulomatous disease that can affect multiple organs, including the lymph nodes, muscles, and abdomen, potentially explaining all the symptoms.
• Infectious Mononucleosis: Caused by Epstein-Barr virus, it can lead to lymphadenopathy, abdominal pain (due to splenomegaly), and sometimes elevated CK levels if there is muscle involvement.

Do Not Miss Diagnoses

• Rhabdomyolysis: A serious syndrome due to direct or indirect muscle injury, leading to the death of muscle fibers and release of their contents into the bloodstream. This can cause a significant elevation in CK levels. While abdominal pain and LN swelling might not be primary symptoms, they could be present in certain contexts (e.g., severe illness, dehydration).
• Acute Lymphoblastic Leukemia (ALL) or Acute Myeloid Leukemia (AML): These can present with lymphadenopathy, abdominal pain (due to hepatosplenomegaly), and elevated CK levels in some cases, especially if there is muscle or bone marrow involvement.

Rare Diagnoses

• Gastric Lymphoma with Muscle Metastasis: A rare scenario where a gastric lymphoma metastasizes to muscle tissue, causing elevated CK levels, abdominal pain from the primary tumor, and lymphadenopathy.
• Eosinophilia-Myalgia Syndrome: A rare condition characterized by elevated eosinophils, muscle pain, and sometimes elevated CK levels. Abdominal pain and lymphadenopathy could be part of the systemic symptoms.
• Inflammatory Myopathies with Associated Malignancies: Though rare, some inflammatory myopathies are associated with an increased risk of malignancies, which could explain the lymph node swelling and abdominal pain in addition to the elevated CK levels.