Smooth muscle antibodies have rarely been reported in dermatomyositis. Its coexistence is not well known nor whether there is an association of autoimmune hepatitis with dermatomyositis. Also, the rash in dermatomyositis can be refractory to standard treatment of dermatomyositis.
We report such a case of new onset florid dermatomyositis with skin features and myositis along with abnormal liver function tests and presence of anti-smooth muscle antibody.
A 19 year-old woman presented with a month history of constitutional symptoms including fatigue, pruritus and a macular eruption over the lateral aspect of her left arm. The rash progressed to involve nasal and periorbital regions with swollen eyelids (Figure 1a) as well as characteristic Gottron papules over her knuckles and erythematous plaques on the arms, knees and legs (Figure 1b). She had progressive aching in the muscles, which she described as if she had ‘run a marathon’, and had difficulty going up and down the stairs, dressing and combing her hair. There was no concurrent fever, chills, jaundice, joint, bladder or bowel symptoms nor any respiratory symptoms. She did not have hair loss or sicca symptoms.
On clinical examination apart from the characteristic rash, she had tenderness of her forearms which were swollen and taut. She had difficulty in squatting and abducting her arms overhead with moderate muscle weakness. There was no hepatosplenomegaly.
Her full blood count, renal function, glucose, thyroid function, rheumatoid factor, immunoglobulin levels, ANCA, LKM antibodies, anti-mitochondrial antibodies (AMA), thyroid antibodies, ESR and CRP were all normal. Her hepatitis A, B, C, CMV and EBV viral serology were negative. Her echocardiogram, chest x-ray and pulmonary function tests were normal.
She had positive antinuclear antibodies (homogenous and cytoplasmic staining at 1/640) and positive smooth muscle antibodies (at 1/640 titre). The extractable nuclear antibodies and dsDNA antibodies were negative, C3 and C4 complement levels were normal, myositis panel (which tests for Mi2, Ku, PM-Scl 75 & 100, Jo1, SRP, PL7 & 12, EJ, OJ and Ro52) were negative. Her alanine transaminase (ALT) was 237U/L (n=<20) and aspartate transaminase (AST) was 247U/L (n=<40) and creatinine kinase (CK) was 1479 U/L (n=30–180). The serum albumin, serum globulin, immunoglobulins and protein electrophoresis were normal. Nerve conduction studies showed marked myopathic motor units consistent with myopathy and the deltoid muscle biopsy confirmed inflammatory myositis (Figure 1c and d). Liver biopsy was not felt to be indicated by gastroenterology at this time. A diagnosis of dermatomyositis was made.
She was commenced on methotrexate 15mg weekly and prednisone (1mg/kg/day) and bone protection. Her transaminases and creatinine kinase normalized. Muscle weakness resolved to baseline slowly. Her skin failed to improve until hydroxychloroquine 400mg daily was added.
Dermatomyositis is an uncommon heterogenous autoimmune inflammatory disease characteristically affecting the skin. Specific pathognomonic patterns of rash occur (heliotrope discoloration around eyes, Gottron papules, V-sign, Holster sign, Shawl sign, etc.) as well as inflammation of skeletal muscles. Current data strongly suggest a pivotal role of both the innate and adaptive immune systems in its pathogenesis.1
Anti-smooth muscle antibodies (ASMA) have only rarely been reported in dermatomyositis.2–6 It is not clear if there is coexistence between dermatomyositis and autoimmune hepatitis. Though her liver function tests (LFTs) have normalised with the treatment, the possibility of autoimmune hepatitis cannot be ruled out. Her positive anti-smooth muscles antibodies have persisted which heightens the suspicions of its co-existence. Our patient is being closely followed up for any relapse of abnormal LFTs in which case liver biopsy for diagnostic confirmation and histological grading will be contemplated and justified.
Autoimmune conditions can cluster with autoimmune thyroid disease reported as the most common coexistent autoimmune disease.7 Primary biliary cirrhosis6,8,9 has been reported rarely with autoimmune inflammatory myositis. However, our patient had normal immunoglobulins and the anti-mitochondrial antibody (AMA) was not detected.