Association of normal nailfold end row loop numbers with a shorter duration of untreated disease in children with juvenile dermatomyositis

Juvenile dermatomyositis (JDM) is a systemic vasculopathy characterized by skin and muscle involvement. Diagnostic criteria include muscle weakness and rash, electromyographic evidence of myopathy, muscle biopsy demonstrating inflammatory infiltrate with or without atrophy, and elevated muscle enzymes, although muscle enzymes may be normal (1). The etiology of JDM has not been established, but evidence suggests that environmental triggers such as an antecedent infection may play a role (2). Many children with JDM have a TNFα–308A allele which is associated with vascular occlusion(3) and increased TNF-α production (4). In addition, JDM disease activity has been associated with decreased absolute numbers of CD3−CD56+/16+ NK cells and elevated von Willebrand factor antigen (vWF:Ag) levels (5). Genes involved in immune responses, including those related to dendritic cell maturation and vasculature remodeling, are expressed at higher levels in muscle biopsies from children with greater duration of untreated disease (6). One particular manifestation of JDM is the presence of abnormal nailfold capillaries, evidenced by capillary dropout, capillary dilatation, and bushy loops (7). Nailfold capillaroscopy (NFC) is a noninvasive, reproducible technique that provides information about abnormalities in periungual microvasculature. It takes into account quantitative measurements of capillary density or end-row loop (ERL) loss as well as the presence of avascularity and abnormal capillaries represented by “bushy” or “bizarre” loops (7,8). ERL scores between 7.0 and 11.5 have been observed in healthy children without JDM or other recognized autoimmune diseases (9). Serial nailfold capillary observations have demonstrated progression of nailfold changes over time in children with JDM (6), 10- 12) and their degree of morphologic changes may correlate with the clinical course of the disease (10). While abnormal NFC are not part of the Bohan and Peter criteria for dermatomyositis, they may reflect systemic vasculopathy, and the data can be used to evaluate patients with JDM (13). ERL regeneration is associated with a shorter duration of untreated disease, a unicyclic disease course resulting in discontinuation of all immunosuppressive therapy before 36 months (versus non-unicyclic in which continuous or repeated immunosuppressive therapy is required), and a lower skin disease activity score (DAS), (11), (12). Lower numbers of ERL in children with JDM are also associated with decreased bioavailability of oral prednisolone compared with intravenous methylprednisolone, suggesting a relationship between systemic vasculopathy and decreased absorption of oral prednisolone (14). Another recent study also showed that six months after diagnosis, the presence of abnormal nailfold capillaries with Gottron’s papules predicted a longer time to remission (15). Given the potential uses of NFC in providing valuable clinical information with regard to JDM, we studied untreated children fulfilling criteria for definite/probable JDM for the following: 1) the association of normal ERL at the time of diagnosis with clinical and laboratory data, and 2) predictors of decreased number of ERL over time.