Homozygous R627W mutations in POLG cause mitochondrial DNA depletion leading to encephalopathy, seizures and stroke-like episodes.

Mutations in the mitochondrial DNA maintenance gene POLG (DNA Polymerase Gamma, Catalytic Subunit), encoding mitochondrial DNA polymerase gamma (pol γ), are associated with an extremely broad phenotypic spectrum. We identified homozygous POLG c.1879C>T; p.R627W mutations in two siblings from a consanguineous South Asian family following targeted resequencing of 75 nuclear-encoded mitochondrial genes. Both patients presented with encephalopathy, seizures and stroke-like episodes, and mitochondrial DNA depletion was confirmed in the proband's muscle tissue. Subsequent Sanger sequencing of POLG in a further 275 unrelated probands with genetically unconfirmed mitochondrial disease revealed a third unrelated proband with a similar phenotype harboring homozygous c.1879C>T; p.R627W mutations and a fourth patient, with a milder clinical disorder, harboring compound heterozygous POLG c.1879C>T; p.R627W and c.2341G>A; p.A781T mutations. Given endogamous practices in the Indian subcontinent, homozygous POLG c.1879C>T; p.R627W mutations should be excluded in South Asian patients presenting with encephalopathy, seizures and stroke-like episodes.

Patterns of peripheral neuropathy in Sjogren's syndrome in a tertiary care hospital from South India.

INTRODUCTION: Sjogren's syndrome (SS) is a systemic autoimmune disease that apart from involving the exocrine glands can affect any organ. Involvement of the peripheral nervous system results in a wide spectrum of neuropathic manifestations. OBJECTIVE: To evaluate the clinico-electrophysiological patterns as well as pathological characteristics of neuropathy in SS patients presenting to a neuromuscular clinic in a tertiary hospital from South India. MATERIALS AND METHODS: This is a retrospective study from the Departments of Neurology, Rheumatology, and Pathology from Nizam's Institute of Medical Sciences. Twenty-one patients with the diagnosis of SS and peripheral neuropathy, seen between 2010 and 2016 were analyzed. Clinical records, conventional nerve conduction studies, and lip and nerve biopsy reports were collected. RESULTS: Twenty one patients with SS had associated neuropathy. Female-to-male ratio was 2:1. In 14 (66.7%) patients, neuropathy was the initial manifestation, while in 4 (20%), exocrinopathy preceded neuropathy. The patterns of neuropathy included mononeuropathy multiplex (MNM) in 7 patients (30%), ganglionopathy in 4 (20%), length-dependant trigeminal autonomic neuropathy, and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) in 2 (10%), and cranial neuropathy in 1 (10%). Eighteen (86%) were seropositive with either anti Ro/SS-A or anti La/SS-B antibodies. Schirmer's test was positive in 13 (61.9%) patients. Nerve biopsy showed vasculitis in 5 patients and demyelinating and axonopathy in 2 patients each. CONCLUSIONS: We conclude that neuropathy is frequently the initial presentation of SS. MNM is the most common pattern followed by ganglionopathy. The pattern of neuropathy helps in arriving at the diagnosis of SS. Serology is a useful initial laboratory test. However,confirmation of SS is not by mere serology. Schirmer's test and lip biopsy are equally essential for the diagnosis, especially in seronegative patients when the clinical index of suspicion is high.