The devastating health consequences of the Zika virus for infected newborns may extend past the brain, suggests new research published Tuesday in The BMJ.
Researchers examined the medical records of seven Brazilian infants infected with Zika while in the womb who also were diagnosed with a congenital joint condition known as arthrogryposis. The newborns all had underlying neurological damage, most notably the forming of calcium deposits in the brain and shrunken brain volume, but no physical abnormalities within the joints themselves. Importantly, at least one case of arthrogryposis was seen in an infant without microcephaly, or a smaller than normal head.
Though it’s still too soon to be completely sure that the joint deformities were caused by Zika, the researchers concluded that microcephaly is likely far from the only health problem that comes with congenital Zika infection.
“This disease goes beyond microcephaly, with other symptoms such as visual and hearing impairment, and unusual signs and symptoms different from other congenital infections,” the authors wrote, adding that microcephaly and other Zika-caused impairments should be seen as part of a broader congenital Zika syndrome.
A child with arthrogryposis is born with joint contractures. Contractures happen when otherwise flexible, stretchy muscles become permanently hardened and shortened. Though most commonly found in the limbs, contractures can also happen in the jaw and spine. In arthrogryposis, these contractures can leave children with rigid limbs and fingers frozen in place that make walking impossible, though cases vary in severity. Seventy to 80 percent of cases are tied to other neurological conditions, but before Zika, no virus or bacteria known to infect developing fetuses was thought to cause arthrogryposis. None of the children in the study tested positive for these other cognitive infections, adding more support for Zika’s role.
Without more research, though, it’s impossible to know how Zika can cause arthrogryposis. Offering an educated guess, the researchers theorized that the virus might directly interfere with the development of motor neurons that send signals to the limbs or wreak havoc on the arteries and veins that provide nourishment to the muscles. Because it may take years for other skeletal or muscular deformities to show up in Zika-infected children, they recommended that these children should receive follow-up evaluations by an orthopedist, even if they already were examined at birth.