Burden of rare genetic disorders in India: twenty-two years' experience of a tertiary centre.

BACKGROUND: Rare disorders comprise of ~ 7500 different conditions affecting multiple systems. Diagnosis of rare diseases is complex due to dearth of specialized medical professionals, testing labs and limited therapeutic options. There is scarcity of data on the prevalence of rare diseases in different populations. India being home to a large population comprising of 4600 population groups, of which several thousand are endogamous, is likely to have a high burden of rare diseases. The present study provides a retrospective overview of a cohort of patients with rare genetic diseases identified at a tertiary genetic test centre in India. RESULTS: Overall, 3294 patients with 305 rare diseases were identified in the present study cohort. These were categorized into 14 disease groups based on the major organ/ organ system affected. Highest number of rare diseases (D = 149/305, 48.9%) were identified in the neuromuscular and neurodevelopmental (NMND) group followed by inborn errors of metabolism (IEM) (D = 47/305; 15.4%). Majority patients in the present cohort (N = 1992, 61%) were diagnosed under IEM group, of which Gaucher disease constituted maximum cases (N = 224, 11.2%). Under the NMND group, Duchenne muscular dystrophy (N = 291/885, 32.9%), trinucleotide repeat expansion disorders (N = 242/885; 27.3%) and spinal muscular atrophy (N = 141/885, 15.9%) were the most common. Majority cases of ß-thalassemia (N = 120/149, 80.5%) and cystic fibrosis (N = 74/75, 98.7%) under the haematological and pulmonary groups were observed, respectively. Founder variants were identified for Tay-Sachs disease and mucopolysaccharidosis IVA diseases. Recurrent variants for Gaucher disease (GBA:c.1448T > C), ß-thalassemia (HBB:c.92.+5G > C), non-syndromic hearing loss (GJB2:c.71G > A), albinism (TYR:c.832 C > T), congenital adrenal hyperplasia (CYP21A2:c.29-13 C > G) and progressive pseudo rheumatoid dysplasia (CCN6:c.298T > A) were observed in the present study. CONCLUSION: The present retrospective study of rare disease patients diagnosed at a tertiary genetic test centre provides first insight into the distribution of rare genetic diseases across the country. This information will likely aid in drafting future health policies, including newborn screening programs, development of target specific panel for affordable diagnosis of rare diseases and eventually build a platform for devising novel treatment strategies for rare diseases.

Acquired hyperexcitable peripheral nerve disorders: Clinical and laboratory features, therapeutic responses, and long-term follow-up.

INTRODUCTION/AIMS: Hyperexcitable peripheral nerve disorders (HPNDs) are rare. Although their clinical and laboratory features have been well studied, information on treatment and follow-up is limited. The aim of this study is to explore the long-term clinical, investigative, and therapeutic profile of patients with acquired HPNDs. METHODS: This study retrospectively analyzed patients from a single tertiary care center with HPND (January 2012 to January 2022). Patients were recruited according to published inclusion and exclusion criteria. Details of clinical features, diagnostic tests, therapeutic interventions, and follow-up were recorded. This study included patients with follow-up of 2 or more years. RESULTS: A total of 32 patients (M = 26, F = 6) were studied. The common clinical features included myokymia, neuropathic or shock-like pain, cramps, sleep disturbances, encephalopathy, cerebellar ataxia, and seizures. A total of 81.25% of patients responded favorably to corticosteroids and membrane stabilizers. Among the nonresponders, five received intravenous immunoglobulin (IVIG), and one received plasma exchange (PLEX). Two patients required rituximab due to poor responses to the above treatments. The mean duration of response was 6 weeks (4-24 weeks) from the initiation of treatment. All patients had favorable outcomes, reaching clinical remission within 1-5 years from the initiation of treatment. Only two patients had relapses. Immunotherapy could be stopped in 78% of patients within 3 years and 100% by 5 years. DISCUSSION: Chronic immunosuppression starting with corticosteroids is required for satisfactory outcomes of HPNDs. These disorders usually run a monophasic course, and relapses are uncommon.

Chronic immune polyradiculopathies: Three clinical variants of one disease?

INTRODUCTION: Chronic immune polyradiculopathies (sensory, motor, and mixed) are uncommon. METHODS: In this single-center, retrospective study, the inclusion criteria for participants were progressive sensory ataxia and/or areflexic limb weakness; tibial somatosensory evoked potential (SSEP) abnormalities of the N22 and P40 potentials with normal sensory and motor nerve conduction studies or root involvement, according to magnetic resonance imaging (MRI); and albuminocytological dissociation. RESULTS: Eight patients were included in our study. Two had weakness, two had sensory ataxia, and four had both weakness and ataxia. Patients with weakness had abnormal SSEPs and patients with sensory ataxia also had absent F waves. Electromyography showed chronic denervation. MRI scans confirmed thickening and enhancement of roots. The patients responded to corticosteroid treatment. DISCUSSION: The overlapping clinicoelectrophysiological findings and similarities in radiological and therapeutic responses suggest that these entities are clinical variants of the same disease. The terms CIS(m)P, CI(s)MP, and CISMP (for chronic immune sensory motor polyradiculopathy) could be used to denote the predominant clinical involvement.

Optimizing Investigations for Evaluation of Enlargements of the Roots, Plexuses and Nerves: A Study of 133 Patients.

BACKGROUND AND AIMS: A wide variety of neurological diseases result in clinical and/or radiological enlargement of nerves, roots and plexuses. With the advancement in techniques and use of magnetic resonance neurography (MRN), aided by electrophysiology, proximal segments of the lower motor neuron (LMN) can be well studied. The relative merits of investigative modalities have not been well defined and comprehensive information on this subject is sparse. METHODS: This retrospective study included data from January 2010 to June 2018. Patients having clinical and/or radiological enlargements of lower motor neuron were included. Clinical and laboratory work up, electrophysiology, MRN and biopsy studies were documented and analyzed. RESULTS: 133 patients fulfilled the inclusion criteria. The diagnostic categories were of leprosy (32%), immune neuropathies (27.8%), nerve infiltrations (8.2%), inherited neuropathies (9%), diabetic radiculopathies (9%) and others (12.7%). MRN was essential to diagnosis in 24.8% and supportive in 31.5% patients. Electrophysiology was essential in diagnosis in 70.6%, biopsy in 45.8% and genetic studies in 6.4% patients. CONCLUSION: The manuscript presents a large cohort of diseases causing enlargement of LMN with clinical and investigative aspects of 7 patients of the most unusual condition of chronic immune sensorimotor polyradiculopathy (CISMP) and details of 7 other patients with chronic mononeuropathies at non-entrapment sites. A table of comparative utility and an algorithm depicting the optimization of investigations has been presented.

Guidelines versus ground lines: Tuberculosis of the central nervous system.

AIM: This questionnaire-based national survey is aimed at understanding the patterns of practice of various aspects of central nervous system (CNS) tuberculosis (TB) among neurologists. SETTINGS AND DESIGN: Neurology department of a tertiary medical college. MATERIALS AND METHODS: A questionnaire was sent through email to all practicing neurologists in India. The responses were analyzed. STATISTICAL ANALYSIS: Inferential statistics. RESULTS: In all, 144 responses were received (out of the 853 questionnaires sent). The major discrepancies were in the primary antitubercular drug regimen (HRZE + HR), duration for tubercular meningitis (TBM) [12 months] and tuberculoma (12-18 months) to develop, follow-up (varied), linezolid use (varied), proportion of drug-resistant cases (<25%), and not taking histological aids (91%). The cerebrospinal fluid (CSF) TB polymerase chain reaction (PCR) utility (75%), not using CSF adenosine deaminase [ADA] (58%), the strategy to stop antitubercular drugs, and the use of steroids (77%) were according to guidelines. CONCLUSION: The present survey, for the first time, provides ground-level evidence of various aspects of CNS TB as practiced by neurologists in India. The major diversity was observed in therapeutics such as the choice of antitubercular drugs, its duration, linezolid use beyond the recommended duration, and knowledge of drug resistance. The monitoring aspects of CNS TB also showed variations. The investigational aspects of CNS TB such as using TB PCR, not using CSF ADA, and regular neuroimaging revealed a good clinical practice. Other CSF parameters require uniformity. This survey thus helps to identify areas of future work in CNS TB in India.

Making sense of the clinical spectrum of limb girdle muscular dystrophies.

The expansion of the spectrum of limb girdle muscular dystrophies (LGMDs) in recent years means that neurologists need to be familiar with the clinical clues that can help with their diagnosis. The LGMDs comprise a group of genetic myopathies that manifest as chronic progressive weakness of hip and shoulder girdles. Their inheritance is either autosomal dominant (LGMD1) or autosomal recessive (LGMD2). Their prevalence varies in different regions of the world; certain ethnic groups have documented founder mutations and this knowledge can facilitate the diagnosis. The clinical approach to LGMDs uses the age at onset, genetic transmission and clinical patterns of muscular weakness. Helpful clinical features that help to differentiate the various subtypes include: predominant upper girdle weakness, disproportionate respiratory muscle involvement, distal weakness, hip adductor weakness, 'biceps lump' and 'diamond on quadriceps' sign, calf hypertrophy, contractures and cardiac involvement. Almost half of patients with LGMD have such clinical clues. Investigations such as serum creatine kinase, electrophysiology, muscle biopsy and genetic studies can complement the clinical examination. In this review, we discuss diagnostic clinical pointers and comment on the differential diagnosis and relevant investigations, using illustrative case studies.

Clinico-Electrophysiological and Genetic Overlaps and Magnetic Resonance Imaging Findings in Charcot-Marie- Tooth Disease: A Pilot Study from Western India.

BACKGROUND: Charcot-Marie-Tooth (CMT) disease is clinically and genetically heterogeneous. There are no published series describing clinical, electrophysiological, and genetic information on CMT from the Indian subcontinent. Magnetic resonance imaging (MRI) neurography technique provides useful information about the plexus and roots and can be employed in patients with CMT. SETTINGS AND DESIGN: A prospective, observational study carried out at a tertiary care hospital in Western India. SUBJECTS AND METHODS: CMT patients fulfilling the UK Genetic Testing Network criteria were included. They underwent clinical, electrophysiological, radiological, and multigene panel testing. RESULTS: Totally 22 patients (19 males, 3 females; 18 sporadic and 4 familial cases) were studied. Pes cavus (19), hammer toes (16), and scoliosis was seen in 1 patient. Electrophysiology revealed motor predominant neuropathy with 15 demyelinating (10 uniform and 5 multifocal) and 7 axonal patterns. Thickened lumbosacral plexuses on MRI neurography were evident in 6/10 studied patients, all 6 having demyelinating neuropathy. Genetic analysis identified PMP22, GJB1, SH3TC2, HSPB1, SPTLC2, MPZ, AARS, and NEFH gene mutations. CONCLUSIONS: This small series documents the pattern of CMT neuropathies as seen in Western India. Clinico-electrophysiological and genetic diagnosis showed general concordance some overlaps and reiterated advantages of gene panel testing in this heterogeneous group of neuropathies. MRI neurography was useful as an additional investigation to detect nerve enlargement in patients with demyelinating neuropathies.

Myotonic Dystrophy Type 1 Clinical, Electrophysiological and Molecular Characterization: Experience at Tertiary Care Centre.

OBJECTIVE: Myotonic dystrophy type 1 (DM1) is the most common myotonic disorder. Molecular genetic testing of the Dystrophia Myotonica-Protein Kinase DMPK gene to detect expansion of CTG repeats is confirmatory. TP-PCR (Triplet Primed-Polymerase Chain Reaction) is rapid and effective screening for the CTG repeat expansions in myotonic dystrophy. Indian data regarding clinical and genetic evaluation of DM1 are sparse. MATERIAL AND METHODS: This was a prospective observational study at a tertiary neurology centre. It included subjects having clinical and electrophysiological evidence of myotonia with CTG repeat expansion of DMPK gene demonstrated by TP-PCR. Diagnostic molecular assessment was done by two-step procedure; conventional PCR and Fragment length analysis followed by TP-PCR. RESULTS: Seventeen patients fulfilled the inclusion criteria. There were fifteen males and two females, with age ranging from 19 to 53 years (mean age 33years). In the phenotype, large calves were seen in three patients and ophthalmoparesis and scapular winging were seen in one patient each. Screening of patients by PCR-Fragment analysis identified all 17 cases to be of DM1. Further confirmatory test by TP-PCR also successfully identified the cases to be of DM1. TP-PCR technique using forward combination primers was used successfully in detecting expansion of CTG repeats in 13 cases whereas in remaining 4 cases reverse primer combination was used successfully. CONCLUSIONS: This series establishes that a combination of PCR- Fragment analysis and TP-PCR is simple and cost effective in determining the diagnosis of Myotonic dystrophy type 1. This study also documents a new clinical observation of calf hypertrophy in genetically confirmed patients with DM1.

Reversible central neural hyperexcitability: an electroencephalographic clue to hypocalcaemia.

A 23-year-old male patient presented with cognitive decline and seizures. Examination revealed Chvostek's and Trousseau's signs. Investigations revealed hypocalcaemia, hyperphosphatemia and normal intact parathyroid hormone levels. Imaging showed calcifications in bilateral basal ganglia, thalamus and dentate nuclei. Interictal electroencephalogram showed theta range slowing of background activity and bilateral temporo-occipital, irregular, sharp and slow wave discharges, which accentuated during hyperventilation, photic stimulation and eye closure. Appearance of epileptiform discharges after eye closure, hyperventilation and photic stimulation may suggest presence of central neural hyperexcitability due to hypocalcaemia. These features may be an equivalent of peripheral neuromuscular hyperexcitability (Chvostek's and Trousseau's signs) that occurs in hypocalcaemia. The clinical and electroencephalographic features completely reversed with correction of serum calcium without antiepileptic medications. It is important for clinicians to recognise these reversible changes, as it can help to avoid misdiagnosis and long-term administration of antiepileptic becomes unnecessary.

Two cases of chronic immune sensorimotor polyradiculopathy: Expanding the spectrum of chronic immune polyradiculopathies.

INTRODUCTION: Immune-mediated demyelinating radiculopathies restricted to proximal sensory or motor roots are uncommon. METHODS: We report the clinical, electrophysiological, biochemical, and radiological features in 2 patients with chronic immune sensorimotor polyradiculopathy (CISMP). RESULTS: The patients presented with sensory ataxia, weakness of the lower limbs, and areflexia. Electrophysiological studies revealed involvement of proximal sensorimotor roots, as evidenced by changes in somatosensory evoked potentials, F-waves, and H-reflexes. In contrast, the distal nerve segments were normal. Magnetic resonance neurography findings of thickened and enhanced roots supported the electrophysiological findings. The response to immunosuppressive therapy was favorable in both patients. CONCLUSION: The findings from these 2 patients further expand the knowledge spectrum of immune polyradiculopathies. Muscle Nerve 55:135-137, 2017.

Do longer necks predispose to Hirayama disease? A comparison with mimics and controls.

BACKGROUND: Dynamic changes in cervical spine during flexion is a proposed mechanism for Hirayama disease [HD], a localized form of anterior horn cell disorder. Apparent shortening of dura as compared to vertebral column leading to dural shift on flexion is considered to be the primary mechanism in this hypothesis. Whether this disproportion is a result of short dura or longer cervical segment is not known and neck length has not been studied in HD. Also, all patients with segmental motor weakness and wasting of upper limbs do not show dural changes; hence comparative evaluation of HD and its mimics is important. MATERIAL AND METHODS: Patients with segmental wasting and weakness limited to upper limbs were subjected to flexion MRI. A special pillow was designed to provide fixed flexion angle of 35°. Patients showing dural changes formed the HD group while rest formed the non-HD group [mimics]. Both groups were analyzed on clinical, electrophysiological and radiological parameters. Whole spine to neck ratio of patients in HD group was compared to the non-HD group and age matched controls. RESULTS AND CONCLUSIONS: Patients with HD had longer cervical segments as compared to the non-HD group and age matched controls [p=0.001]. The longer cervical segment, in combination with dural changes probably contributes to the pathophysiology of dynamic flexion hypothesis of HD and the onset around the growth spurt. Patients with HD had cold paresis and finger extensors were consistently weaker than flexors. Apart from longer necks, cold paresis and pattern of weakness may help to differentiate HD from its mimics.