Pediatric anti-HMGCR necrotizing myopathy: diagnostic challenges and literature review
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LETTER TO THE EDITOR
Pediatric anti-HMGCR necrotizing myopathy: diagnostic challenges and literature review Daniele Velardo 1
&
Irene Faravelli 2 & Claudia Cinnante 3 & Maurizio Moggio 1 & Giacomo Pietro Comi 1,2
Received: 9 February 2020 / Revised: 16 May 2020 / Accepted: 28 May 2020 # Fondazione Società Italiana di Neurologia 2020
Dear Editor-in-Chief, A 7-year-old boy presented with a 2-month subtle onset, progressive lower limb weakness with marked difficulty in getting up from the ground. Creatine kinase (CK) level at presentation was 10,000 U/L. No previous infection was reported, and family history was apparently negative for neuromuscular disorders. Neurological exam revealed proximal weakness of all limbs (Medical Research Council [MRC] grade 4, more pronounced at the level of iliopsoas muscles, MRC grade 3) and need for one-hand support to get up from the ground. Multiplex Ligation-Dependent Probe Amplification (MLPA) analysis of Duchenne Muscular Dystrophy (DMD) gene showed no deletion or duplication. Therefore, the patient underwent muscle biopsy (left biceps brachii), which showed a dystrophic pattern with numerous necrotizing and rare regenerating fibers (Fig. 1). In immunohistochemistry analyses, dystrophin and beta-sarcoglycan binding alterations were observed in rare fibers, but western blot analyses highlighted dystrophin, alpha-dystroglycan, calpain-3, dysferlin, and α- to δ-sarcoglycans normal molecular weights and amounts. Fukutin-related protein and acid alphaglucosidase genetic investigation also resulted normal. Limbgirdle muscular dystrophy (LGMD) next generation sequencing (NGS) panel did not reveal any known pathogenic mutations. Lower limb muscle magnetic resonance imaging (MRI) * Daniele Velardo [email protected] 1
Neuromuscular and Rare Diseases Unit, Department of Neuroscience, Foundation IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122 Milan, Italy
2
Neurology Unit, Neuroscience Section, Department of Pathophysiology and Transplantation, Dino Ferrari Centre, Foundation IRCCS Ca’ Granda Ospedale Maggiore Policlinico, University of Milan, Via Francesco Sforza 35, 20122 Milan, Italy
3
Neuroradiology Unit, Foundation IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Via Francesco Sforza 35, 20122 Milan, Italy
showed relative hypotrophy of proximal muscles (i.e., gluteus maximus, thigh adductors, and posterior compartment of thigh) with only mild fibro-adipose substitution but without significant signs of edema (Fig. 2). Echocardiography was normal. During the next 4 months, while work-up results were pending, no therapy was administered. However, the patient complained of rapidly progressive fatigue, weight reduction with mild swallowing dysfunction, difficulty in climbing stairs, and loss of running ability. Simultaneously, the patient developed dermatologic manifestations characterized by small bald patches of alopecia on the scalp, self-limiting recurring roughening, and cracking of hand fingertips and erythematous papular lesions on ears
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