Table 3.

Histopathological characteristics of ICIAM versus IMNM patients

	ICIAM	IMNM	P value
Number	11	38
Mean age at time of biopsy	68	60	0.08
Clinical phenotype:
Oculobulbar	6a	0
Generalized	5	38	<0.001
Distribution of necrotic fibres
Multifocal clusters	10/11	0/36	<0.001
Scattered	1/11	36/36b
Necrotic fibres per LPF, median (range)	3.78 (0.4–40)	4.7 (1.5–55)	0.7
Regenerating fibres per LPF, median (range)	5 (0–14.6)	8.4 (1–65)	0.003
Inflammation	3/11	13/38c,d	0.7
Endomysial	1/3	8/13	<0.001
Perimysial	2/3	9/13	0.4
Invasion of non-necrotic fibre (autoaggression)	0/11	2/38	0.36
Non-rimmed vacuoles, n	2/11	14/38	0.4
Internalized nuclei, n	0/11	8/38	<0.001
Fibre splitting, n	0/11	9/28	<0.001
Fibre type grouping, n	7/11	11/38	0.02
Increased connective tissue	9/11	24/38	0.4
Endomysial	3/11	1/38
Perimysial	6/11	23/38
Cytochrome C oxidase-negative fibres, n	9/11	21/38	0.003
Cytochrome C oxidase-negative fibres per LPF, median (range)	1.3(0–5.4)	0.31(0–7.5)	<0.01
Ragged-blue fibres, n	8/11	26/38	<0.01
Ragged-blue fibres per LPF, median (range)	0.67 (0–1.71)	0.14 (0–4)	<0.01
Increased acid phosphatase reactivity in connective tissue, n	8/11	3/38e	<0.001
Sarcoplasmic congophilic deposits, n	1/11	2/38	0.5

LPF = lower power field.

All bold values indicate P-value < or = 0.05.

^aMuscle biopsies were taken from triceps (n = 3), splenius capitis (n = 1), biceps (n = 1) and deltoid (n = 1). These muscles were not clinically affected but had myopathic changes on needle EMG.

^bMuscle biopsy slides were not available for review in two patients.

^cFour patients had endomysial and perimysial inflammation.

^dOf 13 patient with inflammation, 9 were positive for HMGCR antibodies and the remaining were seronegative.

^eTwo patient were HMGCR antibody positive.