Inborn errors of immunity and measles. Case report with fatal outcome

The role of postmortem diagnosis is not only to establish the true cause of death, but also to provide feedback to the physician, the health care system and the patient’s relatives. Identifying the true cause of death can save sibs, future children, and sometimes even the patient’s parents. According to the 2024 classification, there are 555 different forms of inborn errors of immunity, and 17 phenocopies, but many of the patients remain undetected both in life and after death. Inborn errors of immunity (or primary immunodeficiencies) often mimic and hide under the mask of other diseases. Infections in patients with inborn errors of immunity may be atypical, persistently recurrent, and may be life-threatening, leading to death or disability of the patient. The same is true for measles, which in immunodeficient patients of any genesis may develop atypically, often with absent or delayed mucosal and cutaneous rashes, and with typical lung lesions. This article describes a clinical case of pneumonia with probable combined lesions from measles and SARS-CoV-2 viruses complicated by bacterial infection. In this case, an equilibrium translocation of long arm regions between chromosomes 7 and 18 was detected in the patient, his sibs and mother. Although this chromosomal pathology is not listed in the classification of inborn errors of immunity, the list of included diagnoses has been continuously expanding, and the presence of inborn immunodeficiency in this clinical case was confirmed morphologically. The National Association of Experts in Primary Immunodeficiencies has developed warning signs of primary immunodeficiencies that may help in the lifetime diagnosis of these diseases. Neonatal screening for the TREC and KREC markers of lymphopenia helps to identify conditions accompanied by defects in T- and B-lymphocyte maturation, and thymus ultrasound is proved to be an essential diagnostic method that helps to detect changes in thymus (one of the main organs of the immune system) size and structure during life. Morphological study, performed either at lifetime during operative thymus resection or postmortem, allows to reveal characteristic signs of immune system dysembryogenesis, including disturbance of thymus size and histological structure, decrease in the number and changes in the size of Hassall’s corpuscles. Thus, based on clinical, morphological and genetic data it reduces a chance of missing primary immunodeficiency, whereas timely diagnostics opens a window for therapeutic intervention and life-saving.