# Clinical and neuroimaging features of familial hemophagocytic lymphohistiocytosis

## TL;DR

This study examines brain imaging and clinical features in children with a rare immune disorder called familial hemophagocytic lymphohistiocytosis.

## Contribution

The study identifies specific brain imaging patterns and clinical features associated with different genetic mutations in familial hemophagocytic lymphohistiocytosis.

## Key findings

- Neurological symptoms were present in 39.4% of children with familial hemophagocytic lymphohistiocytosis.
- White matter brain changes were most common, with RAB27A mutations linked to more severe neurological and imaging features.
- Cerebral volume loss was observed in 78.6% of cases, with UNC13D mutations associated with higher cerebral atrophy scores.

## Abstract

Hemophagocytic lymphohistiocytosis is a non-malignant immune regulation disorder, with activation of uncontrolled inflammatory processes and multiorgan damage; primary hemophagocytic lymphohistiocytosis is genetic.

To analyze clinical and brain magnetic resonance imaging features in children with familial hemophagocytic lymphohistiocytosis.

This retrospective study included 28 children with molecularly confirmed hemophagocytic lymphohistiocytosis. Clinical and laboratory manifestations at initial presentation and upon reactivation were recorded. Routine brain magnetic resonance imaging scans were reviewed and severity scores were calculated for different molecular types.

Eleven (39.4%) children presented with neurological symptoms, 13 (46.4%) with developmental delays, and four with altered levels of consciousness. Lesions predominated in white matter (39.3% subcortical, 35.7% periventricular, and 7.1% central), although 25% had gray matter involvement; 78.6% of the cases presented with cerebral volume loss. Brain stem, cerebellar, and meningeal involvement were observed in 14.3%, 25%, and 7.1%, respectively. The most common mutations were in UNC13D (53.6%), PRF (21.4%), RAB27A (17.9%), and STBXP2 (7.1%); of the children with these mutations, neurological symptoms were observed in 20%, 50%, 80%, and 50%, respectively. Central nervous system reactivation was more prevalent in patients with RAB27A mutations (60%). White matter changes were noted in 16.7% of PRF cases, predominantly involving central regions, whereas 80% of RAB27A cases exhibited periventricular white matter abnormalities. RAB27A mutations were associated with higher white matter severity scores, whereas UNC13D mutations had higher cerebral atrophy scores.

Variable imaging manifestations were observed in familial hemophagocytic lymphohistiocytosis, with white matter involvement predominating. Patients with RAB27A mutations had more frequent clinical and imaging-based neurological involvement.

The online version contains supplementary material available at 10.1007/s00247-025-06454-5.