Patient has polycythemia vera, as evidenced by erythrocytosis, granulocytosis, and headaches & diziness. EPO is decreased due to erythrocytosis. Decreased LAP would indicate CML, not PV.
"PV is a neoplastic (clonal) blood disorder with autonomous (EPO-independent) erythroid proliferation. Because of the existence of a negative feedback mechanism, the erthrocytosis in PV down-regulates EPO production and results in below normal serum EPO levels. In contrast, an EPO-driven erythrocytosis characterizes secondary erythrocytosis, and this condition may be associated with either high or normal serum EPO levels."
Increased Levels of Myeloid cells ( Erythrocytosis, thrombocythemia, and granulocytosis) plus Dizziness and Headache increase the suspicion for Polycythemia vera.
Low EPO in PV due to Negative feedback on EPO release by kidney.
Primary polycythemia = Disorder of Increased no of RBCs, usually due to acquired JAK2 mutation. May present as intense itching after shower (aquagenic pruritus). Rare but classic symptom is erythromelalgia (severe, burning pain and red-blue coloration) due to episodic blood clots in vessels of the extremities. There is DECREASED EPO (vs 2° polycythemia, which presents with endogenous or artificially raised EPO). Treatment: phlebotomy, hydroxyurea, ruxolitinib (JAK1/2 inhibitor).