Self-healing reticulohistiocytosis is a rare, benign, self-limited variant of Langerhans cell histiocytosis (LCH). It is categorized based on the number of involved sites and further classified as congenital or late-onset. In congenital self-healing histiocytosis (Hashimoto-Pritzker disease), the eruption is often widespread, but solitary lesions are reported in 25% of cases. The incidence is around 5 cases per million, although this may be underreported due to the high rate of spontaneous resolution. Males and females are equally affected, and there seems to be a higher prevalence among Whites. As a variant of LCH, it is a clonal proliferative disorder; however, the etiology remains unknown.

In solitary self-healing reticulohistiocytosis, a red-brown painless papulonodule manifests at birth or in the neonatal period, commonly on the head, neck, or distal extremities. Mucous membrane lesions are rare. The papule may become crusted over the following weeks, with spontaneous involution over a 3- to 4-month period. Some lesions may resolve with hypopigmented, hyperpigmented, or atrophic scarring. Typically, there are no recurrences, no systemic symptoms, and no visceral involvement. Since relapses in skin lesions or at extracutaneous sites have been reported up to 4 years after resolution of the initial lesion, and because it is difficult to differentiate the condition from LCH, a skin biopsy, systemic evaluation, and close follow-up should be performed. Overall, however, the prognosis is good.   

Reports of other findings in relation to solitary self-healing reticulohistiocytosis include:

• Lesion(s) urticating from physical manipulation (pseudo-Darier sign).
• Ocular involvement that resolves concurrently with cutaneous lesions.
• Multiple lung cysts that resolve within 1 year.
• Hepatosplenomegaly of unknown clinical significance.