Israel Medical Association Journal

Inflammatory myopathies include polymyositis, necrotizing autoimmune myositis, dermatomyositis, juvenile inflammatory myopathy, and inclusion body myositis. These diseases are classified based on the different clinical and pathological characteristics unique to each of them [1]. Dermatomyositis is a rare disease with an incidence of 6–10 cases/1,000,000 a year with the highest incidence in the 7th decade of life as reported by a Norwegian cohort in a Caucasian population [2].

Diagnosis of dermatomyositis is based on typical signs and symptoms combined with laboratory results, imaging, and electromyography findings and muscle biopsy. Historically, the diagnosis of dermatomyositis was based on the classification criteria named after Bohan and Peter published in 1975. Many other classification criteria were proposed subsequently, the latter by the European League Against Rheumatism/American College of Rheumatology (EULAR/ACR), which were published in 2020 [3].

The clinical features of dermatomyositis are diverse. Skin manifestations can accompany or precede muscle weakness. Classical skin findings include periorbital heliotrope rash and a rash of the upper chest, back, and shoulders, known as the V sign and shawl sign respectively, as well as the Gottron's papules on the knuckles. Another skin appearance is subcutaneous calcifications that break periodically through the skin causing ulcerations. Dermatomyositis usually manifests as a symmetrical proximal muscle weakness but can present with preserved strength called amyopathic dermatomyositis [1].

Paraneoplastic syndromes are reported in 8–15% of patients diagnosed with cancer [1]. They are defined as syndromes that occur due to an underlying malignancy, which has yet to be diagnosed, or at the time of the diagnosis and less frequently following the diagnosis of a malignancy. Several mechanisms are involved including autocrine and paracrine mediators, hormones, peptides, cytotoxic lymphocytes, and cytokines [1,2].

Paraneoplastic syndromes are disorders associated with cancer but without a direct effect of the tumor mass or its metastases on the nervous system. Small cell carcinoma of lung associated with paraneoplastic sensory neuronopathy and/or paraneoplastic encephalomyelitis with the presence of anti-Hu antibodies has been termed “anti-Hu syndrome. Anti-­Hu associated PSN-PEM is an immune disorder in which both cell-mediated and humoral mechanisms are involved. Patients are consiaered affected by Anti-Hu associated PSN-PEM when they develop clinical signs and symptoms of CNS dysfunction and/or sensory neuropathy not caused by metas­tases or other disorders, and serum or cerebrospinal fluid is positive for Hu abs. SCLC is found in more than 90% of patients with cancer and positive Hu abs. Individual patients with Hu abs associated to SCLC may suffer PSN-PEM, Iimbic encephalitis, brainstem encephalopathy, opsoclonus-myoclo­nus, paraneoplastic cerebellar degeneration or myelopathy. Hu abs have a specificity of 99% and sensitivity of 82% in detecting paraneoplastic neurological syndromes. There are two types of treatment: the first is to treat the cancer, the second is to suppress the immune reaction with the use of corticosteroids, cyclophosphamide, azathioprine, plasma ex­change, intravenous immunoglobulin and immunoadsorption however, treatment of paraneoplastic syndromes is generally unsatisfactory.