IgG4-related disease: a novel, important but easily missed condition

IgG4 related pericardium and lung disease in pediatric patient complicated with fatal massive hemoptysis: a case report and review of literature

BACKGROUND

IgG4-related disease (IgG4-RD) is a progressive and sometimes fatal disease that rarely affects pediatric age group. It may affect the orbits, lacrimal and salivary glands, pancreas, kidneys, peritoneum and other organs. Lung and pleura are not commonly reported in IgG4-RD. We here present a rare case of pediatric IgG4-RD with rare involvement of pericardium, pleura and lungs.

CASE PRESENTATION

A 13-year-old girl presented with intrathoracic IgG4-RD with pleuropericardial involvement. She showed initial improvement on prednisolone. Azathioprine and then mycophenolate failed to control relapses during steroid tapering. Her last relapse was treated by rituximab however, the patient developed acute fatal massive hemoptysis.

CONCLUSIONS

Pediatric IgG4-RD is a rare entity with pericardio-pulmonary affection as the rare of the rare. Usual treatment of prednisolone and steroid sparing agents should be used, with rituximab used as a rescue therapy, but fatal complications may occur.

Value of serum IgG4 in differential diagnosis of IgG4-related disease from other autoimmune diseases

AIM: To investigate the value of serum IgG4 in differential diagnosis of IgG4-related disease (IgG4-RD) from other autoimmune diseases (AIDs).

METHODS: Clinical data for 15 patients with IgG4-RD and 187 patients with other autoimmune diseases who were treated at the First Affiliated Hospital of Fujian Medical University from July 2012 to February 2014 were retrospectively. Other AIDs included autoimmune hepatitis (AIH, n = 29), systemic lupus erythematosus (SLE, n = 30), rheumatoid arthritis (RA, n = 32), Sjögren syndrome (SS, n = 26), dermatomyositis (n = 13), adult onset still disease (n = 4), ankylosing spondylitis (AS, n = 15), systemic sclerosis (Scl, n = 11), and microscopic polyangiitis (n = 27). Serum IgG and IgG4 levels were measured with a rate nephelometer. ROC curves were then constructed to identify the optimal serum IgG4 cutoff value for diagnosing IgG4-RD and evaluating its sensitivity and specificity.

RESULTS: The median level of serum IgG4 in patients with IgG4-RD was 3.85 g/L (2.99-9.98 g/L), significantly higher than those in patients with other AIDs (P < 0.01). Serum IgG4 level was the highest in AS among groups of other AIDs (P < 0.01). Serum IgG4 levels were above 1.35 g/L in IgG4-RD patients. Elevated serum IgG4 levels were also observed in more than 10% of patients with AS, Scl and polyangiitis. The optimal cutoff value for the diagnosis of IgG4-RD was 2.09 g/L, and the sensitivity and specificity were 100% and 97.69%, respectively. The area under the curve (AUC) was 0.998. In all groups with other AIDs, the elevation rate of serum IgG4 level was less than 10% when the cutoff point was set at equal to or more than 2.09 g/L. Thus, the specificity of serum IgG4 was greatly improved.

CONCLUSION: Elevated serum IgG4 levels are observed in not only patients with IgG4-RD but also those with other AIDs. Using a cutoff point of 2.09 g/L, serum IgG4 could better differentiate IgG4-RD from other AIDs.