Congenital self-healing reticulohistiocytosis is a condition that is a self-limited form of Langerhans cell histiocytosis.
[2]: 720 Non-specific inflammatory response, which includes fever, lethargy, and weight loss.
This is suspected of being a genetic disorder, and as the name implies, is self healing.
It was first described by Ken Hashimoto and M. S. Pritzkar in 1973.
[4][5]