crystal storing histiocytosis
Definition An über rare–less than 100 cases in the world literature–complication of low-grade B cell lymphoma and monoclonal gammopathies, including myelomas, which is characterised by lysosomal storage of kappa light chain crystals
Clinical findings It may be associated with adult Fanconi syndrome, chronic tubulo-interstitial nephritis with accumulation of monoclonal kappa light chain crystals within proximal tubular cells
Differential diagnosis Benign rhabdomyoma
Micro Sheets of macrophages and histiocytes filled with multiple needle-shaped, periodic acid-Schiff-negative refractile crystals (left image). CD68 positivity (right image) confirms macrophage/histiocytic lineage of cells.
Molecular pathology CSH is due to unique mutations in the V domains of monoclonal kappa light chains that differ from Fanconi syndrome.
References Nephrol. Dial. Transplant. (2010) 25 (9): 2982-2990
Head Neck Pathol. 2012 Mar;6(1):111-20.