Objective

To explore the clinical characteristics of a child with primary immunodeficiency diseases（PID）caused by PIK3CD gene mutation combined with primary ciliary dyskinesia（PCD）and review related literature.

Methods

A case of child （patient 1）with PID caused by PIK3CD gene mutation combined with PCD diagnosed by genetic testing and bronchial mucosal electron microscopy in the West China Second University Hospital，Sichuan University，in February 2021 was selected for the study.The clinical data and results of genetic testing and bronchial mucosal biopsy electron microscopy of patient 1 were analyzed by retrospective analysis method.Literature related with PID combined with PCD in domestic and foreign databases was reviewed using the retrieval strategy set in this study.The procedures followed in this study conformed to the standards set by the Ethics Committee of West China Second Aniversity Hospital，Sichuan University and were approved by the committee （Approval No.2022-074）.

Results

①Patient 1 was a 11 years and 3 months boy who hospitalized for"nasal obstruction，purulent nasal discharge for 2⁺years and cough for 20⁺days".He had recurrent respiratory infections.Physical examination at admission suggested that scattered enlarged lymph nodes could be palpated in the bilateral neck，axilla，and groin，and congestion of nasal mucosa and turbinate swelling，and purulent secretion were found in the nasal cavity.Results of relevant auxiliary examinations at admission showed an immunoglobulin （Ig）G3 level of 0.065 g/L，which was lower than the normal reference value.Genetic testing showed that patient 1 had a missense mutation c.3061G ＞A （p.E1021K）in the PIK3CD gene.Electron microscopy of bronchial mucosal biopsy showed that the epithelial cilia of bronchial mucosa of patient 1 were abnormal with the structure of"9+2"，and the endo-and exo-dynamic protein arms were missing.Combining the child's clinical manifestations with the results of genetic testing and bronchial mucosal biopsy electron microscopy，he was diagnosed with PID caused by PIK3CD gene mutation combined with PCD.He was given comprehensive treatment including anti-infective therapy，regular gammaglobulin infusion，and pulmonary rehabilitation，and his condition was improved with decreased frequency of respiratory infections.②Results of literature review：according to the search strategy set for this study，one piece of literature related to children with PID combined with PCD was retrieved，involving four children with humoral immunodeficiency combined with PCD （patient 2 to 5）.Including patient 1 in this study，a total of five children were analyzed.The age of onset of these five children ranged from 7 to 13 years old，with an average age of 9.8 years old.All five cases had a history of chronic cough，bronchiectasis，chronic sinusitis，and recurrent ear infections.Patient 1 with c.3061G＞A （p.E1021K）mutation in PIK3CD gene had a reduced IgG3，patient 2 had a reduced IgG，and patient 4 had a reduced Ig A and IgG3，both of patient 2 and patient 4 were not subjected to genetic test.Patient 3 had decreased Ig A，Ig M，IgG2，and IgG3，and a homozygous DNAH11 mutation was detected，and patient 5 had decreased Ig A，and a double allele DNAH11 mutation was detected.

Conclusions

PID caused by PIK3CD gene mutation combined with PCD can cause recurrent respiratory tract infections with poor clinical outcomes.Combining clinical features，genetic testing，and bronchial mucosal biopsy electron microscopy results，early diagnosis and treatment can improve the prognosis of children with PID caused by PIK3CD gene mutation combined with PCD.