Xanthogranuloma family
Xanthogranuloma family
The JXG family of disorders is rare, but constitutes the most frequently encountered types of non-Langerhans cell histiocytosis. Common to all subtypes is a proliferation of histiocytes and Touton-type giant cells, with a characteristic phenotype, displaying features of both macrophage and dendritic cell differentiation. Thus, the histologic appearances of all subtypes of ‘xanthogranuloma’ are similar and, for practical purposes, indistinguishable. Nevertheless, they have a broad clinical spectrum of disease, with many parallels to that seen in LCH. Manifestations include patients with solitary or multiple skin lesions, presentation with large deeply situated masses, and widespread disease with systemic involvement. As in LCH, the majority of cases with disseminated and/or systemic disease occur in children, most within the first 10 years of life, and half before the age of 1 year. Solitary lesions may be seen at any age. Although biologically a benign disorder, a variety of clinical outcomes may be experienced. There is a high tendency for cutaneous lesions to undergo spontaneous resolution, but systemic lesions may persist for long periods of time and cause significant, site related, morbidity. Progression of disease is encountered in some rare instances.
JXG constitutes the largest group. Most patients are children with solitary or multiple skin lesions, soft tissue or visceral tumors with rare mucous membrane involvement and systemic disease. Patients presenting with generalized disease are subdivided on the basis of age and distribution of lesions, into benign cephalic histiocytosis (children, localized to skin), generalized eruptive histiocytoma (young adults, localized to skin) and xanthoma disseminatum (XD) or ECD (adults with systemic disease). XD almost always has a cutaneous component. ‘Xanthogranulomatous’ disorders in middle-aged adults and the elderly usually manifest as progressive nodular histiocytosis. Other, even less frequently encountered, less well-defined, and rather more spurious entities are also best included within this family of diseases. These include solitary spindle cell xanthogranuloma, scalloped cell xanthogranuloma, and papular xanthoma (PX).
Historically, patients suffering from disorders of this type have been grouped together on the basis of constellations of shared clinical features.
These putative entities show considerable clinical overlap and, in view of their relatively uniform pathological features, are probably best regarded as different manifestations of the same disease process. Nevertheless, the clinical details of each will be outlined separately below, in order that the reader can relate to the pleitropic nomenclature and somewhat confused literature that surrounds these disorders.