Reticulohistiocytosis

  • Reticulohistiocytoma (solitary epithelioid histiocytoma)
    • Adults, single <1cm asymptomatic yellow to red nodule trunk/extremities
    • Spontaneous resolution months/years, can excise
  • Multicentric reticulohistiocytosis (MRH)
    • Adults, skin 1st in 25% cases, yellow/red-brown papules on upper half of body/face, “coral beads” around nails, skin can resolve over time
    • Arthritis 1st in 50% cases, mutilation, “opera glass fingers”, “accordion hand” on x-ray, treatment limited
    • Malignancy in 20-30%, surveyed much like dermatomyositis
  • Pathology
    • Histiocytic infiltrate with giant cells, “ground glass” or oncocytic type cytoplasm (CD68+)
    • Grenz zone