H syndrome: A review of treatment options and a hypothesis of phenotypic variability

H syndrome is a rare autosomal recessive disorder with clinical features comprising: hyperpigmentation, hypertrichosis, hearing loss, heart anomalies, low height, hypogonadism and hepatosplenomegaly. H syndrome results from loss-of-function mutations in SLC29A3 which leads to abnormal proliferation and function of histiocytes. Herein, we discuss the considerable phenotypic heterogeneity detected in a consanguineous Egyptian family comprising of four affected siblings, two of which are monozygotic twin and the possible therapeutics. The phenotypic variability may be attributed to the role of histiocytes in the tissue response to injury. Such variable expressivity of H syndrome renders the diagnosis challenging and delays the management. The different treatment approaches used for this rare entity are reviewed.