A 23-year-old man presented with worsening fatigue, coarse facial features, digital clubbing, and splenomegaly. Laboratory tests revealed severe anemia and bone marrow fibrosis. Genetic analysis identified a pathogenic mutation in the SLCO2A1 gene, confirming a diagnosis of autosomal recessive primary hypertrophic osteoarthropathy type 2 (PHOAR2). Treatment with Etoricoxib, a COX-2 inhibitor, led to gradual improvements in fatigue, reduction of spleen size, and increased hemoglobin levels over six months. This case highlights the association between elevated prostaglandin E2 levels and myelofibrosis in PHOAR2, emphasizing the potential of COX-2 inhibitors in managing symptoms.