We have herein presented the autonomic PNS associated with anti-α3-gAchR, Hu and SOX1 antibodies in a patient with SCLC. This case suggests that symptomatic treatment, immunotherapy, and additional chemotherapy for autonomic PNS may improve the autonomic symptoms and performance status of patients. If patients with cancer suffer from autonomic symptoms, oncologists and neurologists should consider the possibility of autonomic PNS even in advanced cases.
Autoantibodies involved in autonomic PNS include Hu, Yo, CV2, PCA-2, GAD-65, voltage-gated calcium channel (VGCC) and gAchR antibodies [
6]. Autonomic PNS are usually associated with other PNS, such as encephalomyelitis and sensory neuropathy [
6]. Patients with SCLC rarely present with chronic gastrointestinal pseudo-obstruction and OH without other neurological disturbances caused by anti-Hu antibodies [
8,
9]. Autonomic symptoms, therefore, may only manifest as PNS symptoms [
8,
9]. In this case, the patient had three autoantibodies for Hu, gAchR, and SOX-1. Autonomic symptoms were only detected after neurological examination and laboratory tests, and the patient had no other neurological symptoms, including sensory symptoms. With regard to autonomic symptoms, anti-Hu antibodies usually cause chronic gastrointestinal pseudo-obstruction or acute pandysautonomia as part of encephalomyelitis or subacute sensory neuropathy [
6,
7,
10,
11], whereas anti-gAchR antibodies are mainly associated with subacute pandysautonomia [
1,
4,
6]. Anti-SOX-1 antibodies are also detected in Lambert-Eaton syndrome with SCLC [
12,
13]. SOX1 reactivity is predominantly associated with anti-Hu antibodies and SCLC [
14]. Anti-Hu and SOX-1 antibodies target intracellular antigens [
1,
5,
12], while anti-gAchR antibodies target cell surface antigens [
1]. PNS related to antibodies for intracellular antigens respond poorly to immunotherapy; however, PNS related to antibodies for neuronal cell surface antigens usually respond well to immunotherapy [
5]. The patient described herein presented with only autonomic symptoms without other PNS symptoms, along with decreased levels of 24-h urine and serum catecholamine excretion and normal MIBG scintigraphy assessing the sympathetic cardiac nerve terminals. This suggested that autonomic ganglia of the sympathetic nerve were involved. Although symptomatic treatment and chemotherapy for SCLC had an effect on the recovery of autonomic symptoms, IVIg markedly ameliorated the OH, abdominal symptoms, and urinary retention. These results demonstrate that the autonomic symptoms of this patient were caused by antibodies to cell surface antigens, especially anti-gAchR antibodies. About 15% of patients have paraneoplastic autoimmune autonomic ganglionopathy usually associated with SCLC or thymoma [
15]. However, in Japanese patients with autoimmune autonomic ganglionopathy, 10% patients had ovarian tumors, pancreas cancer, mediastinal tumors, and paranasal cancer, but not SCLC [
4]. Paraneoplastic autoimmune autonomic ganglionopathy due to SCLC associated with anti-gAchR antibodies are likely overlooked in Japan.
The management of PNS requires not only immunotherapy but also oncological treatment [
5]. Our patient suffered from autonomic symptoms and his ECOG PS declined. If the cause of the autonomic symptoms were not identified, the patient would have lost the opportunity to receive the additional chemotherapy. Survival from time of diagnosis is 7 month (median) in patients with anti-Hu antibodies [
16]. Anti-gAchR antibodies and anti-Hu antibodies often coexist in patients with paraneoplastic autonomic neuropathy due to SCLC [
17]. Our patient received the symptomatic treatment, immunotherapy, and additional chemotherapy. As a result, our patient was still alive 10 months after admission, and his ECOG PS remains 1 point. Compared with PNS due to anti-Hu antibodies, this case report highlights the improvement in ECOG PS and that ECOG PS could be maintained for 10 months because of the integrated treatment regime [
16]. Furthermore, this case is unique in that the autonomic symptoms responded well to the integrated treatment, despite antibodies for intracellular antigens and neuronal cell surface antigens being simultaneously detected. Even in cases positive for anti-Hu antibodies, if neurological symptoms are only autonomic symptoms, the effects of other PNS related antibodies (i.e. anti-gAchR antibodies) should be considered, and immunotherapy ought to be performed.