Washington: When walking and cognitive delays occur in concert among kids, the combination may lead to a rare and devastating disorder known as Duchenne muscular dystrophy (DMD), say researchers.

Researchers from the Johns Hopkins University found that delays in the onset of walking that occurs between nine and 16 months are common among boys with DMD and often happen alongside cognitive delays.

Toddlers who started walking late were three times as likely to have cognitive delays as those who began walking on time, found the team.

"Our review of patient records shows that delayed walking along with cognitive delays represents an ominous combination that should prompt pediatricians to conduct further testing and could speed up diagnosis and treatment," said Kara Mirski, a medical student at the Johns Hopkins University School of Medicine.

DMD is caused by a defective muscle protein and marked by progressive loss of muscle strength, function and, eventually, inability to walk at all.

In its advanced form, the condition can also compromise the function of the heart and breathing muscles.

For the study, the team examined the clinical records of 107 children with DMD referred to the Johns Hopkins Children's Center between 1989 and 2012 for diagnosis or treatment and found that nearly half (42 percent) had a history of delayed walking (age 16 months or later).

"The bottom line is that any delay in walking should lead to further probing. When late walking occurs in the context of other developmental delays, it should put DMD on every pediatrician's radar as a possible cause," noted Tom Crawford, a paediatric neurologist at the Johns Hopkins Children's Center.

The study was published in the Journal of Pediatrics.