Prevalence of Spinal Muscular Atrophy in India
Limited India-Specific Prevalence Data
The prevalence of SMA in India has not been systematically established through population-based studies, but carrier frequency data from North India suggests a significantly higher disease burden than previously recognized, with a carrier frequency of 1 in 38 individuals. 1
Carrier Frequency and Estimated Disease Burden
A retrospective study from a tertiary care center in North India covering Uttar Pradesh (16.5% of India's population) found an SMA carrier frequency of 1 in 38 (2.6%) among 606 individuals without family history of SMA, which is substantially higher than the global Caucasian carrier frequency of 1 in 40-60. 1
This elevated carrier frequency in North India has important implications for policy making and suggests that population-based screening programs should be considered for the Indian population. 1
Global estimates indicate an SMA incidence of approximately 1 in 6,000 to 1 in 10,000 live births with a prevalence of 1-2 per 100,000 persons, though these figures are primarily derived from European populations and may not accurately reflect the Indian scenario. 2, 3, 4
Diagnostic and Epidemiological Challenges in India
The lack of robust epidemiological data on SMA in India stems from the prohibitively high costs of diagnostic testing (PCR, MLPA, NGS) and therapeutic interventions, which limits accurate case identification and registration. 5
Most published global SMA studies are outdated, rely on clinical rather than genetic diagnosis, are performed in small geographical regions, and predominantly study European populations—making extrapolation to the Indian context problematic. 2
The heterogeneity of SMA phenotypes (ranging from death in utero to symptom-free adults with bi-allelic SMN1 mutations) contributes to diagnostic delays, especially outside specialist clinics, and obscures true disease burden. 2
Disease Characteristics Relevant to Indian Context
SMA Type I accounts for approximately 60% of all SMA cases globally, with the highest mortality within the first year of life. 2, 4
Nutritional deficiencies, particularly calcium absorption issues, have been documented in up to 84% of SMA patients in some populations, which may be particularly relevant given India's existing burden of malnutrition. 6
Need for Population-Based Screening
Given the high carrier frequency of 1 in 38 in North India and the availability of genetic testing methods that achieve up to 95% sensitivity and nearly 100% specificity for detecting homozygous SMN1 deletions, there is an urgent need for population-based newborn and carrier screening programs in India. 1, 3, 4
Carrier testing should be offered to siblings of SMA patients and partners of known carriers to facilitate reproductive planning, with prenatal diagnosis offered to couples who have previously had an affected child (25% recurrence risk). 4