DERMATOMYOSITIS: IMPP Adult-onset Pattern (Also see
IMPP
)
Immune myopathies with perimysial pathology
(IMPP)
DM-IMPP
Inflammation: Perivascular & Perimysial
Internal architecture
Mitochondrial staining
Necrotic fibers invaded by cells
: Acid phosphatase
Perifascicular atrophy & Pathology
Perimysial pathology
: Alkaline phosphatase
Dermatomyositis: Childhood DM-VP pattern
General features
Clinical & Pathologic classification:
Immune myopathies with perimysial pathology
Also see:
Jo-1 antibody-related IMPP
Onset age: More common in adults
Pathology
Perimysial damage common
More necrosis in perifascicular muscle fibers
No reduction of cytochrome oxidase in muscle fibers
Muscle Fiber Pathology
H&E stain
Necrotic & Regenerating muscle fibers in perifascicular regions
Muscle fiber size is variable
Muscle Fiber Internal Architcture
NADH stain
Muscle fibers near the perimysium are small & stain darkly
Hydrolytic enzyme stains
Acid phosphatase stain
Acid phosphatase stained cells
in necrotic muscle fibers
Alkaline phosphatase stain
Alkaline phosphatase stained
perimysial connective tissue
Inflammation: Perimysial
H&E stain
Acid phosphatase stain
Cells may be confined to the perimysium (Left)
Acid phosphatase stain highlights some perimysial cellularity (Right).
Mitochondrial stains
Cytochrome oxidase stain
Muscle fibers in regions of perifascicular atrophy,
retain COX activity unlike the
childhood pattern
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2/24/2013
