Immune Thrombocytopenic Purpura (ITP): This condition is characterized by isolated thrombocytopenia without other significant abnormalities in the blood count, which fits the patient's presentation. ITP is an autoimmune disease where the body's immune system mistakenly attacks and destroys platelets.

Viral Infections (other than dengue): Certain viral infections can cause thrombocytopenia. Although dengue has been ruled out, other viruses like HIV, hepatitis C, or Epstein-Barr virus could be responsible.
Drug-Induced Thrombocytopenia: Various medications can induce thrombocytopenia as a side effect. A thorough drug history is essential to consider this diagnosis.
Chronic Liver Disease: Although liver function tests (LFTs) are normal, chronic liver disease can sometimes present with thrombocytopenia due to splenic sequestration without significant abnormalities in LFTs.

Thrombotic Thrombocytopenic Purpura (TTP): A rare but life-threatening condition characterized by thrombocytopenia, microangiopathic hemolytic anemia, renal failure, neurological symptoms, and fever. Early diagnosis and treatment are crucial.
Heparin-Induced Thrombocytopenia (HIT): If the patient has been exposed to heparin, HIT is a critical diagnosis to consider due to its high risk of thrombosis.
Disseminated Intravascular Coagulation (DIC): Although more commonly associated with abnormalities in coagulation tests, early or mild DIC could present with isolated thrombocytopenia.

Congenital Thrombocytopenias: These are a group of rare disorders characterized by thrombocytopenia present from birth, often with other physical anomalies or syndromes.
Bone Marrow Failure Syndromes: Conditions like aplastic anemia or myelodysplastic syndromes can present with thrombocytopenia among other cytopenias.
Systemic Lupus Erythematosus (SLE): An autoimmune disease that can cause thrombocytopenia, although it usually presents with a constellation of other symptoms and autoantibodies.