The histiocytosis-lymphadenopathy plus syndrome comprises features of 4 histiocytic disorders previously thought to be distinct: Faisalabad histiocytosis (FHC), sinus histiocytosis with massive lymphadenopathy (SHML), H syndrome, and pigmented hypertrichosis with insulin-dependent diabetes mellitus syndrome (PHID). FHC was described as an autosomal recessive disease involving joint deformities, sensorineural hearing loss, and subsequent development of generalized lymphadenopathy and swellings in the eyelids that contain histiocytes (summary by Morgan et al., 2010). SHML, or familial Rosai-Dorfman disease, was described as a rare cause of lymph node enlargement in children, consisting of chronic massive enlargement of cervical lymph nodes frequently accompanied by fever, leukocytosis, elevated erythrocyte sedimentation rate, and polyclonal hypergammaglobulinemia. Extranodal sites were involved in approximately 25% of patients, including salivary glands, orbit, eyelid, spleen, and testes. The involvement of retropharyngeal lymphoid tissue sometimes caused snoring and sleep apnea (summary by Kismet et al., 2005). H syndrome was characterized by cutaneous hyperpigmentation and hypertrichosis, hepatosplenomegaly, heart anomalies, and hypogonadism; hearing loss was also found in about half of patients, and many had short stature. PHID was characterized by predominantly antibody-negative insulin-dependent diabetes mellitus associated with pigmented hypertrichosis and variable occurrence of other features of H syndrome, with hepatosplenomegaly occurring in about half of patients (Cliffe et al., 2009). Bolze et al. (2012) noted that mutations in the SLC29A3 gene (612373) had been implicated in H syndrome, PHID, FHC, and SHML, and that some patients presented a combination of features from 2 or more of these syndromes, leading to the suggestion that these phenotypes should be grouped together as 'SLC29A3 disorder.' Bolze et al. (2012) suggested that the histologic features of the lesions seemed to be the most uniform phenotype in these patients. In addition, the immunophenotype of infiltrating cells in H syndrome patients was shown to be the same as that seen in patients with the familial form of Rosai-Dorfman disease, further supporting the relationship between these disorders (Avitan-Hersh et al., 2011; Colmenero et al., 2012).