DP25: ‘Hard’ diagnoses, unusual overlap and a helping hand from histology

Emily Pender,¹ Conall MacGearailt,¹ Bernadette Lynch¹ and Mary E. Laing^1,2

¹Galway University Hospitals and ²National University of Ireland, Galway, Galway, Ireland

Correlation between systemic sclerosis (SSc) and dermatomyositis is well described [Jablonska, S, Blaszyk M. Scleromyositis (scleroderma/polymyositis overlap) is an entity. J Eur Acad Dermatol Venereol 2004; 18: 265–6]. Association between localized scleroderma (limited plaque morphoea) and dermatomyositis is rare. Furthermore, while dystrophic calcinosis cutis is often observed in juvenile dermatomyositis, it is rare in adults. A 29-year-old woman initially presented with bilateral skin changes to the thighs. Skin biopsy showed focal collagen sclerosis in the deep dermis, with accompanying lymphoplasmacytic perivascular infiltrate in the skin and subcutis, in keeping with plaque morphoea. With potent topical steroids this significantly improved. Four months later, she presented with rash and progressive muscle weakness. Nailfold dermoscopy revealed cuticular overgrowth and telangiectasia. Gottron papules were present at the metacarpophalangeal joints bilaterally. Shawl sign was positive. Previous rash at the site of biopsy-proven morphoea was noted on the thighs. Myositis panel revealed anti-MI-2 antibodies. Antibodies generally associated with SSc were negative. Skin biopsy showed mild epidermal atrophy and mild perivascular chronic inflammation, with mildly increased dermal mucin. Muscle biopsy was consistent with dermatomyositis. The patient commenced methylprednisolone. Rituximab and azathioprine were initiated. Despite prompt treatment, over weeks she developed widespread rash with firm subcutaneous tissue on the lower back, flanks and bilateral thighs. She underwent image-guided deep biopsy of the thighs, revealing large dystrophic calcifications, fat necrosis and fibrosis within the subcutaneous adipose tissue. Scleromyositis overlap between systemic sclerosis and dermatomyositis, is well described (Jablonska and Blaszyk). However, few cases describe localized scleroderma/dermatomyositis overlap (Park JH, Lee CW. Concurrent development of dermatomyositis and morphoea profunda. Clin Exp Dermatol 2002; 27: 324–7). Rituximab has previously been used in scleroderma/myositis overlap to good effect, and was effective in our patient. In scleromyositis, muscle involvement is generally mild, with minimally elevated muscle enzymes. Patients generally respond to low/moderate doses of steroid therapy (Jablonska and Blaszyk). In contrast, our patient had severe myositis and developed widespread calcinosis cutis. This represents an unusual case of dermatomyositis-localized morphoea overlap with severe myositis and calcinosis cutis, requiring treatment with rituximab and azathioprine. Dermatopathology in this case was essential to identify the initial localized scleroderma, the subsequent dermatomyositis and, finally, calcinosis cutis. Without accurate histopathology it was difficult to differentiate between processes on the thighs, in particular, as the differences in the overlying skin were more subtle, highlighting the importance of appropriate tissue sampling for complex presentations such as this case.