Scleroderma-polymyositis overlap syndrome versus idiopathic polymyositis and systemic sclerosis: a descriptive study on clinical features and myopathology

Table 3 Myopathologic markers of muscle biopsy slides

Characteristics	Number	SSc-overlap (n = 24)	Number	PM (n = 24)	Significance (P value)
Necrotic muscle fibers	24	23 (96%)	24	16 (67%)	0.023^b†
Lymphocytic infiltrates	24	15 (63%)	24	13 (54%)	NS
Positive MHC class I staining	12	11 (92%)	18	12 (67%)	NS
Inflammation^a	24	19 (79%)	24	18 (75%)	NS
MAC staining	10	5 (50%)	13	5 (39%)	NS
Fibrosis	19	5 (26%)	24	2 (8%)	NS
Presence of COX-negative fibers	10	3 (30%)	10	6 (60%)	NS

MAC, Membrane attack complex; NA, not applicable; NS, not significant.
^aInflammation is defined as positive MHC class I staining or/and presence of lymphocytic infiltrates.
^bStatistically significant.

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