This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
Histiocytosis-lymphadenopathy plus syndrome is a group of conditions with overlapping signs and symptoms that affect many parts of the body. This group of disorders includes H syndrome, pigmented hypertrichosis with insulin-dependent diabetes mellitus (PHID), Faisalabad histiocytosis, and familial Rosai-Dorfman disease (also known as familial sinus histiocytosis with massive lymphadenopathy or FSHML). These conditions were once thought to be distinct disorders; however, because of the overlapping features and shared genetic cause, they are now considered to be part of the same disease spectrum. While some affected individuals have signs and symptoms characteristic of one of these conditions, others have a range of features from two or more of the conditions. The pattern of signs and symptoms can vary, even within the same family.
All of the conditions in the spectrum are characterized by histiocytosis, which is an overgrowth of immune system cells called histiocytes. These cells abnormally accumulate in one or more tissues in the body, which can lead to organ or tissue damage. The lymph nodes are commonly affected, leading to swelling of the lymph nodes (lymphadenopathy). Other areas of cell accumulation can include skin, kidneys, brain and spinal cord (central nervous system), or digestive tract. The spectrum is known as histiocytosis-lymphadenoapthy plus syndrome because the disorders that make up the spectrum can have additional signs and symptoms.
H syndrome is named for the collection of symptoms – all starting with the letter H – that are commonly present. These include hyperpigmented skin lesions with excessive hair growth (hypertrichosis) and histiocyte accumulation, enlargement of the liver or liver and spleen (hepatomegaly or hepatosplenomegaly), heart abnormalities, hearing loss, reduced amounts of hormones that direct sexual development (hypogonadism), and short stature (reduced height). In some cases, hyperglycemia/diabetes mellitus may also be present.
PHID is characterized by patches of hyperpigmented skin with hypertrichosis and the development of type 1 diabetes during childhood.
Faisalabad histiocytosis is characterized by lymphadenopathy and swelling of the eyelids due to the accumulation of histiocytes. Affected individuals may also have joint deformities (contractures) in their fingers or toes, and hearing loss.
Familial Rosai-Dorfman disease is characterized by lymphadenopathy, most often in the neck. Histiocytes can also accumulate in other parts of the body.
Histiocytosis-lymphadenopathy plus syndrome is caused by mutations in the SLC29A3 gene. The condition is inherited in an autosomal recessive pattern. Treatment is aimed at treating the symptoms present in each individual.
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