Targeting therapy to anticipated phenotype, based on autoantibody profile, in early amyopathic dermatomyositis. A case report.
Dr Karl Kavanagh, Dr Laura Durcan
Beaumont Hospital, Dublin
An emerging body of evidence supports the stratification of therapies in dermatomyositis according to phenotype and antibody subtype. Here we describe the novel case of very early interstitial lung disease associated with classic MDA5 subtype dermatomyositis and our therapeutic approach.
A 22 year old male with a past history of type 1 diabetes presented with an erythematous rash across the dorsum of his hands, digital swelling and generalised, mild, early morning stiffness.
His hands were diffusely swollen with small ulcers at the tips of multiple digits. His rash was scaly and worst across his knuckles associated with ulceration. His face demonstrated a similar erythematous scaly rash along the hair line with erythema of the scalp and at the nape of the neck. His CK was normal as were inflammatory markers. The differential was of dermatomyositis with prominent cutaneous involvement or perhaps psoriasis given the scale and question of dactylitis. He was commenced on methotrexate and a tapering dose of steroids.
Investigations demonstrated positive Ro and Ro-52 antibodies with marginally low C4. An MRI of his thigh demonstrated some mild muscle oedema in the vastus lateralis which was nonspecific, EMG and muscle biopsy were normal. Pulmonary function testing demonstrated a slightly decreased DLCO (86%) with normal volumes. A CT thorax showed subtle subpleural and peribronchovascular groundglass change in the costophrenic regions which persisted on prone views. This was suggestive of early interstitial lung disease.
Given his antibody subtype ( Ro 52/MDA5 ) which is known to associated with a severe spectrum of amyopathic dermatomyositis with cutaneous ulceration with prominent pulmonary involvement and high mortality, we changed him to Mycophenolate Mofetil and worked him up for Rituximab.
Dermatomyositis associated with MDA5 positivity is characterised by prominent cutaneous findings, including in particular cutaneous ulceration and calcification and intersitisial lung disease. Given the severity of the lung disease described in this disease subtype and the associated mortality we proceeded with aggressive immunosuppression despite mild pulmonary involvement. At the time of this case the patient has had almost complete resolution of his cutaneous disease and follow up imaging is pending.