Benign non-X histiocytosis: a unique case bridging several of the non-X histiocytic syndromes

We present a patient with a papular eruption of 4 years' duration that clinically resembled xanthoma disseminatum or the indeterminate cell disorder. On light microscopy his disorder resembled generalized eruptive histiocytoma or the indeterminate cell disorder. Special stains, cultures, and electron microscopy were noncontributory. Indirect immunofluorescence studies with monoclonal antibodies to cell surface markers demonstrated infiltrating cells of monocyte/macrophage lineage (OKM1, MAC-1, HLA-DR, and HLA-DQ positive) rather than Langerhans or indeterminate cell lineage (OKT6 negative). This case may overlap two or more of the previously reported non-X histiocytic syndromes, suggesting that perhaps these syndromes should be viewed as a spectrum of disease rather than as discrete entities. We recommend performing cell phenotyping on all new cases of non-X histiocytosis because clinical, microscopic, and ultramicroscopic findings often prove inadequate for classification.