Evaluation of monoclonal and oligoclonal gammopathies in a pediatric population in a major urban center

The light at the end of the tunnel: an unusual case of acute kidney injury in a pediatric patient: Answers

Monoclonal gammopathies are a rare diagnosis in pediatric patients. A 19-year-old female patient with past medical history of hypogammaglobulinemia and natural killer cell deficiency and stage III follicular lymphoma, in remission, presented with a right-sided pneumonia, noted to have acute kidney injury and proteinuria. Complement C3 and C4 levels were normal. Anti-double-stranded DNA antibodies, antinuclear antibodies, anti-extractable nuclear antigen antibodies, and antineutrophil cytoplasmic antibodies were negative. A renal biopsy showed numerous fractured tubular casts that were periodic acid-Schiff and silver-stain negative and fuchsinophilic on trichrome stain, with associated giant cells, tubulitis, acute tubular injury, and tubular rupture. The tubular casts had 3+ staining for lambda light chains and 0-1+ staining for kappa light chains. These findings were consistent with light chain cast nephropathy (LCCN). Serum free light chains, serum immunofixation, urine protein electrophoresis, and urine immunofixation studies supported the renal biopsy diagnosis of LCCN. A bone marrow biopsy showed normal trilineage hematopoiesis and also revealed an atypical B cell population detected by flow cytometry. Pathology specimens from lesions in the distal small bowel were characteristic of diffuse large B cell lymphoma (DLBCL). Chemoreduction therapy followed by chemotherapy was initiated for the DLBCL. Three months after initiation of chemotherapy, the patient's creatinine has improved by > 50%. The likely cause of her LCCN was the new diagnosis of a DLBCL. Other risk factors include her history of hypogammaglobulinemia, natural killer (NK) cell deficiency, community-acquired pneumonia, and prior follicular lymphoma. Our patient may be the youngest reported case of LCCN. Treatment of LCCN is based on treating the underlying clonal plasma cell or B cell proliferation, typically with chemotherapy.

Maternal T and B cell engraftment in two cases of X-linked severe combined immunodeficiency with IgG1 gammopathy

X-linked severe combined immunodeficiency (X-SCID), caused by defects in the common gamma chain, is typically characterized by T and NK cell defects with the presence of B cells. T cell dysfunction and impaired class-switch recombination of B cells mean that patients typically have defects in class-switched immunoglobulins (IgG, IgA, and IgE) with detectable IgM. Here, we describe two patients with X-SCID with IgG1 gammopathy, in whom we identified maternal T and B cell engraftment. Exclusively, maternal B cells were found among the IgD^-CD27⁺ class-switched memory B cells, whereas the patients' B cells remained naïve. In vitro stimulation with CD40L+IL-21 revealed that peripheral blood cells from both patients produced only IgG1. Class-switched maternal B cells had restricted receptor repertoires with various constant regions and few somatic hypermutations. In conclusion, engrafted maternal B cells underwent class-switch recombination and produced immunoglobulin, causing hypergammaglobulinemia in patients with X-SCID.

Secondary hypertriglyceridemia in children and adolescents

Secondary dyslipidemia with predominant hypertriglyceridemia may occur as a consequence of both common and rare causes. After accounting for obesity and associated insulin resistance, clinicians should carefully consider other contributing factors and conditions. Genetic background and causative factors prevail during gestation, infancy, and childhood and continue in adults. Elevations in triglyceride (TG) are associated with transfer of TG to high-density lipoprotein (HDL) and low-density lipoprotein (LDL) resulting in lipolysis, HDL degradation, and formation of atherogenic LDL particles. Defining and treating the underlying cause is the first step toward restoring the lipids and lipoproteins to normal, especially in cases with severe hypertriglyceridemia, who are at risk for acute pancreatitis. Disorders involving the liver, kidney, endocrine, and immune systems and medications need to be considered. Rare diseases such as lipodystrophy and glycogen storage disease are particularly challenging, and there have been promising new developments. Treatment depends on the severity; prevention of acute pancreatitis being a priority in severe cases and lifestyle modification being a foundation for general management followed by targeting TG and predictors of coronary artery disease such as LDL cholesterol and non-HDL cholesterol, when they exceed cutpoints.