Legs are swollen and could not walk, might be an allergic reaction to his coronavirus disease (COVID) booster shot; Legs are swollen and could not walk, might be an allergic reaction to his coronavirus disease (COVID) booster shot; Legs are swollen and could not walk, might be an allergic reaction to his coronavirus disease (COVID) booster shot; This is a solicited report received from contactable reporter(s) (Other HCP and Consumer or other non HCP). Other Case identifier(s): UNT-2023-008422.  An 80-year-old male patient received BNT162b2, BNT162b2 omi ba.4-5 (BNT162B2, BNT162B2 OMI BA.4-5), as dose number unknown (booster), single (Batch/Lot number: unknown) for covid-19 immunisation; treprostinil (TREPROSTINIL), since 28Feb2023 (Batch/Lot number: unknown) at 32 ug 4x/day for pulmonary arterial hypertension; treprostinil sodium (TYVASO), since 28Feb2023 (Lot number: 000328P, Expiration Date: 30Apr2024) at 32 ug 4x/day for pulmonary arterial hypertension. The patient's relevant medical history included: "Pulmonary arterial hypertension" (ongoing). Concomitant medication(s) included: OPSUMIT. Vaccination history included: Covid-19 vaccine (Primary Immunization series complete; unknown manufacturer), for COVID-19 Immunization. The following information was reported: PERIPHERAL SWELLING (hospitalization), GAIT INABILITY (hospitalization), ALLERGY TO VACCINE (hospitalization) all with onset 19Mar2023, outcome "unknown" and all described as "Legs are swollen and could not walk, might be an allergic reaction to his coronavirus disease (COVID) booster shot". The action taken for treprostinil and treprostinil sodium was unknown. Clinical course: This 80-year-old, 161 lb, male patient began therapy with continued in additional info section. Tyvaso DPI (treprostinil inhalation powder) delivered by Tyvaso dry powder inhaler, on 28Feb2023 for primary pulmonary arterial hypertension. The patient was supplied with Tyvaso DPI 32 ug and the current dose was reported as 32 ug, four times a day (QID), via inhalation (IH) route. On 19Mar2023, 20 days after initiating Tyvaso DPI, the patient was in the hospital due to legs were swollen and could not walk, it might be an allergic reaction due to his coronavirus disease (COVID) booster shot (peripheral swelling, hospitalized; gait disturbance, hospitalized and allergy to vaccine; hospitalized). Co-suspect medication included COVID-19 vaccine. Concomitant medication included Opsumit (macitentan). Relevant medical history included primary pulmonary arterial hypertension. Action taken with Tyvaso DPI was not reported for the events of peripheral swelling, gait disturbance and allergy to vaccine. At the time of reporting, the outcome of peripheral swelling, gait disturbance and allergy to vaccine was unknown. The reporter did not provide causality for the events of peripheral swelling, gait disturbance and allergy to vaccine with Tyvaso DPI. The reporter's causality for the events of peripheral swelling, gait disturbance and allergy to vaccine with COVID-19 vaccine was considered to be possibly related.  Case Comment/ Sender's Comment: The company has assessed the serious adverse events of peripheral swelling, gait disturbance and allergy to vaccine as not related to treprostinil inhalational powder and tyvaso DPI inhaler. The events of peripheral swelling and gait disturbance were likely due to concurrent administration of the COVID-19 vaccine.  The reporter considered "legs are swollen and could not walk, might be an allergic reaction to his coronavirus disease (covid) booster shot" related to BNT162b2, BNT162b2 omi ba.4-5.  The information on the batch/lot number for BNT162b2, BNT162b2 omi ba.4-5 has been requested and will be submitted if and when received.; Sender's Comments: Based on the information currently available, a causal association between the reported events and BNT162b2, BNT162b2 omi ba.4-5 cannot be excluded. The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to RAs, Ethics Committees, and investigators, as appropriate.