Differential Diagnosis for a Child with Positive ANA Titer Screen and Associated Symptoms

Given the child's presentation with a positive ANA titer screen but negative ANA cascade 1,2, and 3, along with low hemoglobin, low MCHC (mean corpuscular hemoglobin concentration), high platelets, normal vitamin D levels, and symptoms of consistent nausea, the differential diagnosis can be categorized as follows:

• Single Most Likely Diagnosis

  • Chronic Disease or Infection: The presence of a positive ANA titer can sometimes be seen in chronic infections or diseases not directly related to autoimmune disorders. The low hemoglobin and MCHC suggest anemia, which could be due to chronic disease. High platelets can also be seen in chronic inflammation or infection. Nausea could be related to the underlying condition causing these lab abnormalities.

• Other Likely Diagnoses

  • Iron Deficiency Anemia: Despite the normal vitamin D levels, iron deficiency could explain the low hemoglobin and MCHC. The high platelet count can sometimes be seen in iron deficiency anemia. Nausea could be a symptom if the anemia is severe enough to cause significant fatigue or if there's an underlying gastrointestinal issue contributing to the iron deficiency.
  • Inflammatory Bowel Disease (IBD): IBD can cause chronic nausea, anemia due to chronic blood loss or malabsorption, and elevated platelets due to inflammation. The positive ANA could be an incidental finding or related to the chronic inflammation.

• Do Not Miss Diagnoses

  • Systemic Lupus Erythematosus (SLE): Although the ANA cascade is negative, SLE should be considered, especially if there are other symptoms suggestive of the disease (e.g., joint pain, rash, renal issues). A negative ANA cascade does not completely rule out SLE, as some patients may have negative tests early in the disease or if they are on certain medications.
  • Malignancy: Certain malignancies, especially hematologic ones, can present with anemia, thrombocytosis (high platelets), and a positive ANA titer. Nausea could be a symptom of the malignancy itself or related treatments.
  • Hemolytic Anemia: This condition involves the premature destruction of red blood cells and could explain the low hemoglobin and MCHC. Some forms of hemolytic anemia can have a positive ANA titer.

• Rare Diagnoses

  • Mixed Connective Tissue Disease: A rare autoimmune disorder that can present with features of lupus, scleroderma, and rheumatoid arthritis. It might have a positive ANA titer and could explain some of the child's symptoms.
  • Autoimmune Hemolytic Anemia (AIHA): A condition where the immune system produces antibodies against the red blood cells, leading to their destruction. It's a rare cause of anemia and could have a positive ANA titer.