Immunohistochemical surfactant protein-A expression: fatal drowning vs. postmortem immersion

The postmortem diagnosis of drowning continues to be one of the most difficult in forensic pathology because of unspecific autopsy findings. It must be always remembered that disposal of a victim body in water is not unknown in homicide. The most important physiological consequence in fatal drowning is hypoxemia. The air-liquid interface of alveoli and distal airways of the mature lung are lined with a thin layer of lung surfactant, composed of phospholipids, proteins and neutral lipids. Surfactant components are synthesized and/or incorporated into lung surfactant in alveolar type II cells, and secreted to form an airspace lining film. The composition and function of lung surfactant is disturbed in cases od acute lung injury (ALI) including drowning. Surfactant protein-A (SP-A) is the most abundant surfactant protein. Surfactant protein-A (SP-A) is secreted by type II alveolar cells and cells. It's immunohistochemical distribution is observed in two different pathways: a linear membranous staining and a granular intra-alveolar staining. We hypothesize the significance of immunohistochemical detection of SP-A and its help in determination of the time of death, and possibly distinguishing of death by immersion vs. postmortem immersion using the morphological analysis applied on SP-A immunohistochemical stained lung tissue samples. We also argue in favor of routine use of SP-A staining in selected forensic cases where pathogenesis includes mechanical asphyxia and lung pathology. Although some studies reached conclusions to define the mechanisms involved in pathogenesis of mechanical asphyxia and aspiration necessity of additional studies arose. The mechanism of the production of massive aggregates remains to be determined. In the mean time the detection of SP-A (immunohistochemical) as well as biochemical is potentially useful tool in the forensic practice with possible application in daily practice.