A unique case of light chain (AL) amyloidosis masquerading as hypophosphatemic osteomalacia.

Light chain (AL) amyloidosis is the result of a clonal plasma cell disorder which causes organ damage by deposition of misfolded light chains. Kidney is a common site of amyloid deposition. Proteinuria, usually in nephrotic range and unexplained renal insufficiency are the main manifestations of renal injury. We report a unique case of renal involvement by AL amyloidosis masquerading as metabolic bone disease. 38 year old male patient presented with progressively increasing diffuse bony pains, low backache and proximal weakness of both lower limbs since two years. On investigation, he was detected to have hypophosphatemic osteomalacia due to renal phosphate loss which was fibroblast growth factor 23 (FGF23)- independent. He also had nephrotic range low molecular weight proteinuria. Renal biopsy to ascertain the aetiology revealed deposition of amyloid fibrils in the glomerular mesangium on electron microscopy. Its characterization by immunofluorescence (IF) was consistent with immunoglobulin light chain (AL) amyloidosis. In the absence of a demonstrable plasma cell clone on bone marrow biopsy, we made a diagnosis of monoclonal gammopathy of renal significance (MGRS). He was treated with chemotherapy following which there was symptomatic improvement and reduction in phosphaturia. This case describes a unique presentation of renal injury due to AL amyloidosis masquerading as hypophosphatemic osteomalacia. The aim of this report is to highlight that hypophosphatemia in adults is usually acquired and treatment of underlying etiology results in cure, unlike in children where genetic counseling and phosphate replacement is the mainstay of treatment.

Role of DNA probes in characterization of pathogenic and non-pathogenic E. histolytica.

Various tests have been described to differentiate the pathogenic and non-pathogenic types of E. histolytica. Recently DNA hybridization has been described to differentiate between the two subtypes. Using common HMC probe the presence of E. histolytica in stool was confirmed. Then on the basis of hybridization with DNA probe P 145 (pathogenic) and B 133 (non-pathogenic) E. histolytica was characterized as being pathogenic and non pathogenic respectively. Out of 137 patients studied 88 were symptomatic and 49 asymtomatic. 65 patients harboured E. histolytica as proved by microscopic examination of stool. Sixty-eight stool samples tested positive for DNA hybridization with common HMC probe, this included 65 microscopy positive samples and 3 microscopy negative samples. This gives a sensitivity of 100% and 96% specificity. All the 68 samples were then subjected to hybridization with P 145 and B 133 DNA probes. Out of 88 symptomatic patients stool samples of 57 patients were microscopy positive, however 58 were positive by common HMC probe and all of these were P 145 (pathogenic) positive and B 133 (non-pathogenic) negative. Of the 49 asymptomatic cases 8 were E. histolytica positive on microscopy and 10 positive on hybridization with common HMC probe and all 10 were P 145 negative and B 133 positive. It can be thus concluded that DNA hybridization is a reliable way to differentiate between pathogenic and nonpathogenic E. histolytica.