Introduction
Myasthenia Gravis (MG) is a rare neurological condition with a
prevalence of 0.2 - 0.4 per thousand [1]. It is characterized by
muscle weakness that worsens after use. In most patients, initial
symptoms involve the extrinsic ocular muscles (EOMs). The symptoms
progress to other bulbar muscles and limb muscles, resulting in
generalized MG. In 10% of the patients, symptoms remain limited to the
EOMs, known as ocular MG [2]. Antibodies to the acetylcholine
receptor (AChR) are found in 85% of patients with generalized MG and
50% of those with ocular MG [3]. The antigenic target defines the
subtypes of autoimmune MG. The most common target of autoantibodies in
MG is the nicotinic acetylcholine receptor (AChR) in approximately 85%
of the patients, followed by muscle-specific kinase (MuSK) and
lipoprotein receptor-related protein 4 (LRP4) in about 15% [4].
Myeloproliferative Neoplasms (MPNs) are disorders due to stem-cell
hyperplasia characterized by an increased peripheral blood cell count,
overactive bone marrow, and proliferation of mature hematopoietic cells
[5]. 2016 WHO category of MPNs includes the three major
subcategories of Janus kinase 2 (JAK2)/ calreticulin (CALR)/
myeloproliferative leukemia virus oncogene (MPL) mutation-related MPNs:
Polycythemia Vera (PV), Essential Thrombocythemia (ET), and Primary
Myelofibrosis (PMF), as well as four other clinic-pathologic entities:
chronic myeloid leukemia (CML), chronic neutrophilic leukemia (CNL),
chronic eosinophilic leukemia, not otherwise specified (CEL-NOS) and
MPN, unclassifiable (MPN-U) [6]. PMF includes pre-fibrotic/early PMF
(pre-PMF) as well [7]. The diagnostic hallmark of CML is the
invariable presence of the BCR-ABL1 mutation [6, 8, 9].
Characteristic bone marrow morphology is required for WHO compliant
diagnosis, especially in distinguishing ET from pre-fibrotic PMF and
masked PV [10].
Paraneoplastic neurological syndromes (PNS) are disorders associated
with cancer, not caused by direct invasion, metastasis, or treatment
consequences. They are autoimmune, rare, but potentially treatable
[10] and can occur before or after primary cancer diagnosis
[11]. The prevalence of these disorders varies with the type of
cancer. PNS occurs in 2–3% of the patients with neuroblastoma or small
cell lung carcinoma (SCLC) and 30–50% of the patients with thymoma.
Overall, 0.5–1% of all patients with cancer have clinically disabling
PNS [10]. PNS are more commonly associated with solid organ
malignancies and very rarely with hematological malignancies.
Hematological malignancies, including myeloproliferative disorders, are
more commonly associated with dermatological paraneoplastic syndromes
such as erythroderma, leukocytoclastic vasculitis, and sweet syndrome;
and rheumatological paraneoplastic syndromes such paraneoplastic
pemphigus and polymyalgia rheumatica [12]. Sweet syndrome is an
acute febrile neutrophilic dermatosis characterized by Acute onset of
tender, erythematous nodules, papules, plaques, or pustules on
extremities, face, or upper trunk along with fever, malaise, and
neutrophilia. Approximately 20% of patients with Sweet syndrome have
underlying hematologic malignancy [13]. In this review, we have
tried to identify case reports in which there is an association between
MG and MPN. These cases have been compared and contrasted to evaluate
whether MG can occur as a PNS in patients with underlying MPN.