An autopsy was conducted on a 29-year-old man with DMD. The deceased had been diagnosed with DMD at the age of 7 years and had been bedridden since early adolescence. Although he was dependent on mechanical ventilation, he was still able to eat and talk and, according to a report by his sister, had been doing as well as usual on the day of his death. A governmental home-care helper visited the house after his sister left for work, and found him unconscious and cyanotic. He died in the emergency room without recovery of spontaneous circulation, despite cardiopulmonary resuscitation.
External examination revealed generalized muscular atrophy and contractures, consistent with previously diagnosed muscular dystrophy. No other injuries were identified, except for those resulting from previous medical interventions such as tracheostomy and percutaneous nephrostomy. Dissection revealed total fatty replacement of the calf muscle. In contrast, the diaphragm and heart were macroscopically normal. During the internal examination, muscle tissues from the calf, diaphragm, and heart were collected to assess the extent of disease involvement. Histological examination of the sampled tissues revealed varying degrees of fibrofatty change in the muscles. Grossly, the muscles of the legs were totally replaced by fatty tissue (
Fig. 1A). Microscopic examination of the calf muscle showed the most extensive replacement, with nearly 100% involvement (
Fig. 1B,
C); furthermore, dystrophin expression was not identified (
Fig. 1D). Although the diaphragm was grossly unremarkable (
Fig. 2A), microscopy revealed multifocal, patchy fibrofatty changes in the diaphragmatic tissue that accounted for approximately 50% of the area (
Fig. 2B). The myocytes adjacent to the affected area contained glassy cytoplasmic inclusions, which stained a deep-red using Masson's trichrome staining (
Fig. 2C). Additionally, loss of dystrophin expression was observed in the remaining myocytes of the diaphragmatic tissue (
Fig. 2D). The heart weighed 305 g and had an unremarkable gross appearance (
Fig. 3A). The cardiac muscle showed the least involvement, with approximately 10% replacement. The fibrofatty changes observed in the heart were confined to the left ventricular wall and interventricular septum, whereas other regions, including both atria, the right ventricular wall, and the conduction system (sinoatrial and atrioventricular nodes), were preserved. The fibrofatty tissue had a distinct appearance, characterized by collagenous fibers resembling a stretched spring (
Fig. 3B,
C). In addition, the complete loss of dystrophin expression in cardiomyocytes further supported the diagnosis of DMD (
Fig. 3D). The myofibers in the affected area displayed a mottled pattern of desmin expression, whereas those in the unaffected area displayed a uniform staining pattern. Furthermore, the changes were more extensive on the left side of the interventricular septum than on the right side (
Fig. 4). In conclusion, the cause of death was attributed to cardiac failure due to the progression of DMD, and the manner of death was classified as a natural death.