Case Report: Recurrent pulmonary infections with neck masses: a diagnostic challenge and literature review.

This article presents a case characterized by recurrent pulmonary infections and a poor therapeutic response. Initially, cystic fibrosis (CF) or Primary ciliary dyskinesia was suspected; however, the patient subsequently sought medical attention for a neck mass. The mass was initially misdiagnosed as lymphoma, but a comprehensive examination and assessment ultimately confirmed the diagnosis of activated phosphoinositide 3-kinase delta syndrome type I(APDS1). Through the patient's tortuous diagnostic journey, this report aims to enhance clinicians' understanding of this rare primary immunodeficiency disorder. Clinical picture: The patient is a female adopted child who has experienced recurrent lung infections since the age of 6 months. On average, she has required hospitalization 2-3 times annually, with conventional anti-infection treatments proving less effective. Throughout her illness, she was admitted to another hospital for sinusitis and breast cysts, although the specifics of her treatment remain unclear. Subsequently, she presented to our hospital with symptoms of coughing, yellow sputum, and hemoptysis. During her hospitalization, a new neck mass was identified. Key inspection: Imaging assessment revealed a chest CT indicating pulmonary infection and bronchiectasis with mucus plug formation. Neck CT and MRI suggested a potential diagnosis of lymphoma. Pathogen testing through nucleic acid analysis for respiratory pathogens yielded positive results for mycoplasma and adenovirus influenzae. Laboratory and abdominal ultrasound did not identify any abnormalities in the pancreas. A peripheral blood immunological assessment demonstrated significantly diminished cellular and humoral immune functions. Following the resection of the cervical mass, the initial pathological diagnosis was lymphoma; however, tests for T-cell receptor (TCR) and immunoglobulin (IG) gene rearrangements returned negative results. After a multidisciplinary consultation and subsequent pathological re-examination, the diagnosis was revised to infectious mononucleosis. Genetic testing revealed a heterozygous mutation in the PIK3CD gene. Final diagnosis: Activated phosphatidylinositol 3-kinase δ syndrome type I (APDS1). Treatment and prognosis: Following diagnosis, the child was administered rapamycin-targeted therapy in conjunction with compound sulfamethoxazole to prevent infections, with regular monitoring of rapamycin blood concentrations. Subsequent follow-up indicated a significant reduction in the frequency of pulmonary infection episodes, a decrease in the size of the enlarged lymph nodes in the neck, and effective control of the condition.