Sinus histiocytosis with massive lymphadenopathy. Report of its occurrence in two siblings with retropharyngeal involvement in both.

Sinus histiocytosis with massive lymphadenopathy (SHML) was found in two siblings, both of whom had retropharyngeal involvement. In one of the children the retropharyngeal swelling appeared to produce obstructive symptoms, requiring excision of the involved lymph nodes. These cases appear to constitute not only the first proven familial occurrence of SHML but also the only reported instances of retropharyngeal involvement. SHML is an uncommon disease of unknown etiology that must be distinguished from other diseases associated with marked lymphadenopathy, particularly as its course is generally benign and not altered by any known form of medical treatment.