15. Myalgia resulting from fasciitis in a difficult to diagnose case of dermatomyositis

INTRODUCTION: Dermatomyositis can be challenging to diagnose as illustrated in this case. Prior to diagnosis this lady was commenced on treatment from her GP, immunology and dermatology for presumed urticaria and recurrent angioedema including courses of steroids which therefore masked symptoms and signs of what was probably always dermatomyositis. In addition of interest this lady describes myalgia and subjective weakness without any objective evidence of myositis however she was noted to have fasciitis and the significance of this will be discussed. CASE DESCRIPTION: We present a case of a 42-year-old physiotherapist originally from Philippines with no significant past medical history. She reported symptoms of urticarial rash and hay fever for approximately 8 years. She attended her GP and eye casualty in summer 2017 with periorbital swelling. She was diagnosed with angioedema and was treated with antihistamines and prednisolone with response but there was a relapse on discontinuation. She attended the immunology allergy nurse specialist February 2018. Bloods for C1 inhibitor deficiency were normal and had already failed high dose antihistamine and montelukast. She was diagnosed as having chronic spontaneous angioedema and occasional urticaria and commenced on omalizumab therapy with limited benefit. She attended dermatology in February 2018. She was on steroids but agreed with the diagnosis of urticaria and angioedema but arranged allergy testing for contact dermatitis due to described rash on chest that had cleared with steroids. At follow up in May 2018, she was diagnosed with eczema and prescribed topical steroids. Her first attendance to rheumatology was in October 2018 and she was on prednisolone 5mg. She had four courses of oral steroids in the preceding six months. In addition to her rash and periorbital oedema she described myalgia, muscle weakness and fatigue for a few months which were steroid responsive. On examination there was mild periorbital oedema, patchy erythema face and anterior chest wall and normal muscle power. FBP, U+E, ESR, CRP, CK, LFTs ANA, complement, myositis and extended myositis panel were all normal. MRI thighs and upper arms in January 2019 showed unusual oedematous changes within the superficial and deep intermuscular fascia with less prominent muscular oedema. Ultrasound guided soft tissue biopsy of the right thigh containing muscle, fascia and adipose tissue showed non-specific inflammation. She was seen again by dermatology, and was off oral steroids but using topical dermovate. The rash distribution was more typical of dermatomyositis with early Gottron’s papules and nailfold erythema. Dermovate was stopped and punch biopsy right upper arm was taken consistent with dermatomyositis. She commenced on methotrexate 10mg and hydroxychloroquine 200mg and at recent review was seen to be improving. DISCUSSION: This was an interesting case as it took approximately 18 months to reach a definitive diagnosis. The original diagnosis of angioedema and urticaria led to treatment with antihistamines and steroids which then masked the clinical symptoms and signs for review with subsequent specialties. It was only really when steroids were weaned that the presentation classically resembled dermatomyositis and led to skin biopsy confirming the diagnosis. During this case the patient for several months described myalgia, muscle weakness and fatigue which responded to steroids. Her MRI showed fasciitis. There was noted to be some intramuscular oedema although less prominent in comparison to the fasciitis. On balance not felt to represent myositis. This was the rationale for the biopsy to contain the fascial layer rather than a purely muscle biopsy. Eosinophilic fasciitis was felt to be a differential. There has always been a query regarding muscle involvement given the patients’ symptoms but there has been no objective evidence of this on imaging or laboratory investigations. Interestingly a paper published in the Journal of Rheumatology in 2017 concluded that myalgia in patients with dermatomyositis was attributable to fasciitis rather than myositis and this is something that could be discussed in more detail if presented orally and may be relevant to this case. KEY LEARNING POINTS: The key learning points of this case being that it can be difficult to diagnose less common conditions like dermatomyositis especially for non-specialists. It is important therefore to question previous diagnoses and make your own assessment especially when treatments have been unsuccessful. In this instance the original diagnosis of angioedema and urticaria was continued forward by subsequent specialties adding weight to the diagnosis on each occasion and it was only when the patient attended rheumatology with muscle symptoms that the diagnosis was reviewed. This was however made more challenging due to steroid use. It was therefore important in this case that treatments in particular steroids were stopped given that there was uncertainty regarding the diagnosis. This was key as it enabled the clinical signs to become more apparent and ultimately a skin biopsy to confirm the diagnosis. Explaining the rationale of stopping treatment to patients is important particularly as they may feel worse temporarily. It is important when considering treatments with steroids and DMARDs which can have long terms side effects that we can justify these. Having histology in these circumstances is invaluable. The assessment and treatment of muscle symptoms in the absence of objective evidence of myositis is an area we would be interested in learning more about. CONFLICTS OF INTEREST: The authors have declared no conflicts of interest.