Erdheim-Chester disease is a rare non-Langerhans cell histiocytosis. It is a multisystem disorder that causes bone pain, exophthalmos, diabetes insipidus, damage to the kidneys and central nervous system and/or cardiovascular symptoms.
The mean age of onset is 53 years, with a male to female ratio of 3:1. The clinical course varies from symptom-free forms to multisystemic, life-threatening ones.
The pathognomonic feature of ECD is osteosclerosis of the long bones, which manifests as bone pain, especially in the distal lower limbs. Infiltration of the pituitary leads to diabetes insipidus and in rare cases to hyperprolactinemia and gonadotropin deficiency.
Furthermore, general symptoms such as fever, weakness and weight loss occur. Consequences of possible infiltration of other organs are increased intracranial pressure, papilledema, adrenal insufficiency, xanthelasmas, and papulonodular skin lesions.
CNS involvement causes cerebellar and pyramidal signs, headache, seizures, cognitive impairment, cranial nerve palsy, and sensory disturbances.
The cause of the disease is unclear, discussing reactive or neoplastic causes. Familial accumulations have not been observed so far. Recent studies show that in patients with ECD increased mutations occur in the proto-oncogene BRAF. Due to the extreme rarity of Erdheim-Chester disease, predicting the prognosis is difficult. The life expectancy depends strongly on the degree of damage to the organs.
In the case of ineffective therapy, the majority of patients die of pneumonia, congestive heart failure, or kidney failure approximately two to three years after diagnosis.