6-Year-Old Girl with Muscle Pain and Swelling in the Thighs


Fig. 23.1

Quadriceps muscle biopsy from this patient. (a) H&E stain, arrows point to the macrophages in perimysium and endomysia connective tissue with granular basophilic cytoplasm. (b) Nonspecific esterase stain, (c) Acid phosphatase stain, (d) PAS stain, (e) CD68 immunostain, (f) Morin stain, (g–h) EM images of macrophages containing spiculated inclusions. (a–c were from cryostat sections. d–f were from FFPE sections. g–h were EM images)



Final Diagnosis


Macrophagic Myofascitis


Patient Follow-up


The patient was started on prednisone 1 mg/kg/day for 2 months, followed by a slow tapering schedule to be weaned off. She had dramatic improvement of her symptoms. Unfortunately, she had recurrent episodes of swelling and muscle pain a year after steroids were weaned off. She was re-started on steroid therapy with a partial control of her symptoms. CK level had been decreasing progressively.


Discussion


Macrophagic myofasciitis is an inflammatory condition associated with aluminum containing vaccines , including DTaP, hepatitis A(HepA), HepB, human papilloma virus (HPV), HIB, and pneumococcal conjugate vaccine (PCV) [1]. The lesion of MMF is restricted to the vaccine injection sites, namely the quadriceps muscle of children and deltoid muscle of adults. Pathologically, the characteristic finding in muscle biopsy is the presence of macrophages that contain aluminum salt derived from aluminum adjuvant-containing vaccines [2]. These macrophages tend to aggregate in the perimysium (Fig. 23.2a) but do not form multinucleated giant cells. A lymphocytic component may be present within the aggregate (Fig. 23.2b, arrow). In cases where the macrophages infiltrate the endomysial compartment, they percolate through the interstitial connective tissue without causing obvious myofiber damage or myofiber MHC1 upregulation (Fig. 23.2c). Morin compound (2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxychromen-4-one) is a flavonoid that forms a green-blue fluorescent complex with aluminum [3]. Morin fluorescence reactivity is strongly positive in the aluminum particles in the cytoplasm of the basophilic macrophages, weakly positively in some nuclei (likely due to the presence of zinc finger transcription factors), but not in myofibers or connective tissue (Fig. 23.1f, Fig. 23.2d). Morin stain is highly specific for MMF, and is negative in granulomatous myositis, sarcoidosis, or inflammatory myositis with abundant macrophages [4].

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Apr 21, 2020 | Posted by in NEUROLOGY | Comments Off on 6-Year-Old Girl with Muscle Pain and Swelling in the Thighs

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