Autopsy Findings in a 16-Week-Old Infant
A comprehensive autopsy of a 16-week-old infant should follow the standardized protocol for Sudden Unexpected Death in Infancy (SUDI), which mandates microbiological sampling from respiratory and central nervous systems, blood cultures, and tissue preservation for molecular analysis, as this age group falls squarely within the SUDI classification. 1
Core Microbiological Sampling Protocol
The autopsy must include the following bacteriological samples with direct bacterial culture (aerobic and anaerobic): 1
- Blood culture (aerobic and anaerobic)
- Cerebrospinal fluid (CSF)
- Nasopharyngeal swab
- Swabs from any identifiable lesions
- Lung tissue
- Spleen
- Intestinal content
Additional samples such as middle ears and urine should also be obtained. 1
Virological Analysis
Viral studies are critical in this age group and should include: 1
- Nasopharyngeal swab
- Lung tissue
- Intestinal content
- Cerebrospinal fluid
These samples require molecular analyses (PCR), with viral cultures performed if necessary. 1
Tissue Preservation for Advanced Testing
Freeze 0.5 cm³ samples at -80°C from the following organs: 1
- Heart
- Skeletal muscle
- Liver
- Brainstem
- Kidney
- Other tissues if clinically relevant
These frozen samples permit future molecular analyses (viral or bacterial) as guided by histology findings. 1
Serum should also be preserved for further serology if needed. 1
Special Considerations for Neurotropic Infections
If disseminated infection with neurotropic viruses (such as human Parechovirus) is suspected, expanded sampling is required: 1
- Cerebellum
- Lung
- Spleen
- Heart
- Bone marrow
- Adrenal gland
- Kidney
- Intestinal content
- Nasopharyngeal swabs
Evaluation for Meningitis
CSF is the most critical sample for confirming or excluding meningitis. 1 A small piece of brain tissue should be obtained for both culture and molecular analyses. 1 If meningitis is identified at autopsy and CSF was not collected before brain removal, swab the meningeal surface to recover exudate for culture and PCR. 1 In cases of exudative meningoencephalitis, both middle ears must be inspected and swabbed after opening the petrous bones. 1
Respiratory System Evaluation
Multisite sampling from both upper and lower respiratory tracts is mandatory, particularly in infants where macroscopic evidence of pulmonary infection may be absent. 1 At minimum, obtain one portion from each lung prior to removing thoracic organs. 1 A swab from the lower lobe bronchi immediately after separating the main bronchi should complement tissue samples. 1
Genetic and Metabolic Considerations
If no obvious cause of death is identified, consider: 1
- Complete autopsy by a pathologist with cardiovascular pathology expertise to exclude channelopathies (14-35% of sudden unexpected deaths in young patients show no abnormalities at standard autopsy)
- Tissue preservation for genetic analysis to determine presence of channelopathies
- Family history review for syncopal episodes, seizures, unexplained accidents/drownings, or sudden death
Critical Pitfalls to Avoid
Failure to obtain adequate microbiological samples before tissue autolysis occurs is the most common error. 1 Samples should reach the laboratory within 2 hours at room temperature or within 48 hours if refrigerated in appropriate transport media. 1
Do not assume a negative gross examination excludes infection—infants frequently lack macroscopic evidence of pulmonary or systemic infection despite fatal infectious processes. 1
Anaerobic cultures should be specifically requested for abscesses, abdominal pathology, intestinal pathologies, or peritonitis, as post-mortem translocation of gastrointestinal flora can confound interpretation. 1
Documentation and Follow-up
External physical examination, medical photographs, and standard radiographic imaging should be performed in all cases. 2 The pathologist performing the autopsy should ideally be trained in perinatal or pediatric pathology. 2 Direct communication between the clinical team and pathologist ensures all necessary sampling is performed appropriately. 2