Efficacy of diffusion-weighted magnetic resonance imaging in detecting infected cysts in a case of polycystic kidney disease.

Hepatic and/or renal cyst infection is a major complication in patients with polycystic kidney disease. In many cases, drainage of infected cysts is necessary, although accurate detection of infected cysts from among the numerous hepatic or renal cysts present is often difficult, because the findings of infected cysts on computed tomography and T1- and T2-weighted magnetic resonance imaging resemble those of normal cysts. We describe here a case of polycystic kidney disease complicated by hepatic cyst infection. On diffusion-weighted magnetic resonance imaging (DWMRI), which is occasionally used in the diagnosis of cerebral abscesses, infected hepatic cysts showed higher signal intensity than other cysts, facilitating differentiation of the cysts requiring drainage from numerous other cysts. Infected cysts showed a marked decrease of the apparent diffusion coefficient (ADC) values compared with those of normal cysts. DWMRI was very effective in detecting infected cysts in our patient and may be of value in other such cases with polycystic kidney disease.

Clonal relationship between infiltrating immunoglobulin G4 (IgG4)-positive plasma cells in lacrimal glands and circulating IgG4-positive lymphocytes in Mikulicz's disease.

Mikulicz's disease (MD) is gaining acceptance as an immunoglobulin G4 (IgG4)-related disease characterized by bilateral lacrimal and salivary gland swelling. The aetiology of MD and other IgG4-related diseases is still unclear. The present work was performed to study the clonality of infiltrating IgG4-positive plasma cells in lacrimal glands and circulating peripheral blood cells in patients with MD, and compare the clonal relationship between infiltrating and circulating IgG4 positive cells. Total cellular RNA was extracted from the lacrimal glands and peripheral blood in five MD patients. Reverse transcription polymerase chain reaction was performed with primers specific for activation-induced cytidine deaminase (AID) and for Ig VH and IgG4. Sequences of Ig VH were compared with the structure of Ig VH of the lacrimal glands and the peripheral blood cells. AID was expressed to varying degrees in lacrimal glands of all MD patients. Most IgG4-positive cells infiltrating lacrimal glands and in peripheral blood were polyclonal, although several clonally related pairs were detected. In one patient, two of the circulating IgG4 VH4-59 clones shared identical CDR3 sequences with the clones within the lacrimal glands. In conclusion, while most tissue-infiltrating and circulating IgG4-positive cells in MD are polyclonal, some clonally related IgG4 positive cells exist between lacrimal gland and peripheral blood, accounting for the clinical features of MD as an IgG4-related disease involving multiple organs.