Sudden infant death syndrome (SIDS) risk reduction campaigns have resulted in a significant decline in the incidence of SIDS.¹ However, SIDS remains the major single cause of death in children in developed countries, with a reported incidence, together with unascertained deaths, of approximately 1/3000 live births.^1,2

SIDS is in essence a diagnosis of exclusion, although there are inconsistencies in how it is applied, and some pathologists feel that it is not adequately defined.^3,4 In a study of the various causes of sudden unexpected death in infancy (SUDI), the most common non-SIDS diagnosis was infection (7.1% of 623 cases), followed by cardiovascular anomaly (2.7%), child abuse (2.6%), and metabolic/genetic disorders (2.1%).⁵ Cardiovascular defects and serious infection are potentially easier to diagnose at necropsy than many of the inherited metabolic disorders that may contribute to SUDI. Importantly, it was noted that a non-SIDS diagnosis was reached much more frequently in centres with expertise in paediatric pathology (18% v 6%).⁵ Therefore, inherited metabolic disorders (IMDs) or other genetic disorders may be underdiagnosed as a cause of SUDI in less specialist centres. IMD as a cause of SUDI will probably constitute a greater proportion of all cases of SUDI as the incidence of total SUDI falls, partly because of a decline in the incidence of other causes of SUDI, and possibly more consistent application of the diagnostic criteria for SUDI; however, an important factor will be improved detection of the various metabolic causes of SUDI.

“Inherited metabolic disorders or other genetic disorders may be underdiagnosed as a cause of sudden unexplained death in infancy in less specialist centres”

Where SUDI occurs in more than one …