SUMMARY A 37-year-old man with a history of seminoma presented with vertigo, ataxia, and diplopia. An autoantibody specific for kelch-like protein 11 (KLHL11) was identified with the use of programmable phage display. Immunoassays were used to identify KLHL11 IgG in 12 other men with similar neurologic features and testicular disease. Immunostaining of the patient’s IgG on mouse brain tissue showed sparse but distinctive points of staining in multiple brain regions, with enrichment in perivascular and perimeningeal tissues. The onset of the neurologic syndrome preceded the diagnosis of seminoma in 9 of the 13 patients. An age-adjusted estimate of the prevalence of autoimmune KLHL11 encephalitis in Olmsted County, Minnesota, was 2.79 cases per 100,000 men.

ROHHAD), is a severe pediatric disorder of uncertain etiology resulting in hypothalamic dysfunction and frequent sudden death. Frequent co-occurrence of neuroblastic tumors have fueled suspicion of an autoimmune paraneoplastic neurological syndrome (PNS); however, specific anti-neural autoantibodies, a hallmark of PNS, have not been identified. Our objective is to determine if an autoimmune paraneoplastic etiology underlies ROHHAD. Methods: Immunoglobulin G (IgG) from pediatric ROHHAD patients (n = 9), non-inflammatory individuals (n = 100) and relevant pediatric controls (n = 25) was screened using a programmable phage display of the human peptidome (PhIP-Seq). Putative ROHHAD-specific autoantibodies were orthogonally validated using radioactive ligand binding and cell-based assays. Expression of autoantibody targets in ROHHAD tumor and healthy brain tissue was assessed with immunohistochemistry and mass spectrometry, respectively. Results: Autoantibodies to ZSCAN1 were detected in ROHHAD patients by PhIP-Seq and orthogonally validated in 7/9 ROHHAD patients and 0/125 controls using radioactive ligand binding and cell-based assays. Expression of ZSCAN1 in ROHHAD tumor and healthy human brain tissue was confirmed. Interpretation: Our results support the notion that tumor-associated ROHHAD syndrome is a pediatric PNS, potentially initiated by an immune response to peripheral neuroblastic tumor. ZSCAN1 autoantibodies may aid in earlier, accurate diagnosis of ROHHAD syndrome, thus providing a means toward early detection and treatment. This work warrants follow-up studies to test sensitivity and specificity of a novel diagnostic test. Last, given the absence of the ZSCAN1 gene in rodents, our study highlights the value of human-based approaches for detecting novel PNS subtypes.

ROHHAD (Rapid-onset Obesity with Hypothalamic Dysfunction, Hypoventilation and Autonomic Dysregulation) is a rare, yet severe pediatric disorder resulting in hypothalamic dysfunction and frequent sudden death. Genetic and other investigations have failed to identify an etiology or diagnostic test. Frequent co-occurrence of neuroblastic tumors (NTs) and cerebrospinal fluid inflammation point to an autoimmune paraneoplastic neurological syndrome (PNS); however, specific anti-neural autoantibodies, a hallmark of PNS, have not been identified. Here, we screened antibodies from a curated cohort of ROHHAD patients (n=9) and controls (n=150) using a programmable phage display of the human peptidome (PhIP-Seq). Our ROHHAD cohort exhibited frequent association with NTs (8/9) and features consistent with autoimmune etiology. Autoantibodies to Zinc finger and SCAN domain-containing protein 1 (ZSCAN1) were discovered and orthogonally validated in 7 of 9 ROHHAD patients, all of whom had NTs, and shown to be absent in non-ROHHAD pediatric patients with NTs. Notably, human ZSCAN1 expression was confirmed in ROHHAD tumor and healthy human hypothalamus. Our results support the notion that tumor-associated ROHHAD is a pediatric PNS, potentially initiated by an immune response to peripheral NT. ZSCAN1 autoantibodies may aid in an accurate diagnosis of ROHHAD, thus providing a means toward early detection and treatment. Lastly, given the absence of the ZSCAN1 gene in rodents, our study highlights the value of human-based approaches in addition to the classical rodent-based approaches for detecting novel PNS subtypes.