PF4 and cutaneous mastocytosis: Logistic regression analysis of concurrent clinical diagnoses or outcome with anti–PF4/P IgG levels in Ret+ CM revealed a significant positive association with death as an outcome (OR = 15.2, 95% CI = 1.02–275; P = 0.048; Table 3), consistent with a role for anti-PF4/P in CM pathogenesis.