Acute myeloid leukemic infiltration of trachea and larynx; This literature case was received from other healthcare professional on 09-Oct-2023 and concerned a 50-year-old, male patient.  The aim of this article is to present a rare and unusual diagnoses in of tracheitis secondary to concomitant autoimmune IgG4-RD and acute myeloid leukemic (AML) infiltration of trachea and larynx.  The patient's current conditions included history of HIV with HAART therapy, chronic cough, dyspnoea, oedematous arytenoids and diffuse bilateral subglottic narrowing with 40% of tracheal lumen visible. The patient's historical vaccines included Covid-19 vaccine (brand not specified) administered on an unspecified date, one year prior the reporting, after which the patient experienced adverse event of cough. The patient's concomitant medications included HAART therapy for HIV. Additionally, the patient denied weight loss, skin rash, joint pains or swelling, smoking history, neck trauma, prior intubation, or family history of cancers or autoimmune diseases.  On an unspecified date in 2023, the patient was vaccinated with influenza vaccine (brand not specified; dose, route of administration, anatomical location, and indication: not reported). The batch number was not reported.  On an unspecified date in 2023, a few days following influenza vaccine, the patient's cough recurred with severe stridor, prompting emergency department visit. The patient was hypoxemic requiring intubation.   On an unspecified date in 2023, the laboratory results were significant for new pancytopenia with neutropenia 2.3 x10^3/mcL and 58% blast cells on peripheral smear. CD4 was 175 and HIV RNA PCR was 40. Direct laryngoscopy and bronchoscopy were performed, and biopsies were obtained. Bone marrow biopsy was performed, and acute myeloid leukaemia (AML) was confirmed by flow cytometry. Promyelocytic leukaemia/retinoic acid receptor alpha (PML/RARA) (15;17) was not detected upon fluorescence in situ hybridization FISH analysis. Tracheal and laryngeal biopsies with immunisations CD34 and CD117 reveal respiratory epithelial mucosa and underlying oedematous stroma with chronic inflammatory cells and leukemic cells infiltration.  At the time of the initial report, the outcome of 'leukemic infiltration pulmonary' was not reported.  The reporter did not provide a causality assessment.  In conclusion this case of tracheitis and upper airway obstruction was unique as both underlying etiologists were rare AML infiltration and IgG4-RD. An elevation of serum IgG4 greater than 2-fold of upper limit of normal had a specificity of 99% for IgG4-RD and was rarely observed in other conditions. Moreover, autoimmune disease occurrence during HIV infection was a rare event. Tracheal involvement of IgG4-RD and AML was uncommon but should be included in the differential diagnosis of tracheal stenosis.  The event of leukemic infiltration was considered to be medically significant by a Physician within Seqirus' Pharmacovigilance and Risk Management Department.   Company comment: A 50-year-old patient with medical history of HIV, chronic cough, dyspnoea, oedematous arytenoids and diffuse bilateral subglottic narrowing, was vaccinated with influenza vaccine. A few days following influenza vaccine, the patient's cough recurred with severe stridor, prompting emergency department visit and requiring intubation. On an unspecified date in 2023, bone marrow biopsy was performed, and acute myeloid leukaemia (AML) was confirmed by flow cytometry. Tracheal and laryngeal biopsies with immunisations CD34 and CD117 reveal respiratory epithelial mucosa and underlying oedematous stroma with chronic inflammatory cells and leukemic cells infiltration. Causal role of the vaccine is assessed as not related for the event of leukemic infiltration, due to biological implausibility. Underlying medical history provide alternative aetiology for the event.; Sender's Comments: A 50-year-old patient with medical history of HIV, chronic cough, dyspnoea, oedematous arytenoids and diffuse bilateral subglottic narrowing, was vaccinated with influenza vaccine. A few days following influenza vaccine, the patient's cough recurred with severe stridor, prompting emergency department visit and requiring intubation. On an unspecified date in 2023, bone marrow biopsy was performed, and acute myeloid leukaemia (AML) was confirmed by flow cytometry. Tracheal and laryngeal biopsies with immunisations CD34 and CD117 reveal respiratory epithelial mucosa and underlying oedematous stroma with chronic inflammatory cells and leukemic cells infiltration. Causal role of the vaccine is assessed as not related for the event of leukemic infiltration, due to biological implausibility. Underlying medical history provide alternative aetiology for the event.