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Joint Disorder Added to List of Potential Zika Effects

Brazilian scientists report arthrogryposis in infants of infected mothers

Scientists in Brazil studying a possible link between Zika virus infection in the womb and severe joint abnormalities (arthrogryposis) in infants say these disorders should be added to the growing list of conditions to watch for, according to a Reuters report.

Arthrogryposis multiplex congenita is characterized by joint contractures at birth, which may be divided into isolated and multiple contractures. Isolated contractures affect only one area of the body, most commonly the foot. The term “arthrogryposis” is often used to describe multiple congenital contractures affecting two or more areas of the body.

The term arthrogryposis is derived from the Greek words arthro (joint) and gryposis (crooked).

In an analysis of seven cases of children with joint deformities, the researchers said that the abnormalities could be a result of the Zika virus’ effect on motor neurons––cells that control the contraction or relaxation of muscles––in developing infants. In all of the cases, the mothers also had a documented Zika infection or a Zika-like rash during pregnancy, or had given birth to a baby with microcephaly.

Because the new research, published in the British Medical Journal, consisted of a retrospective case-series study, it could not provide definitive conclusions on whether the Zika virus was a direct cause of the arthrogryposis.

Two of the seven children tested positive for immunoglobulin M (IgM) antibodies to Zika virus in their cerebrospinal fluid. Arthrogryposis was present in the arms and legs of six children (86%) and in the legs of one child (14%). Hip radiographs showed bilateral dislocation in seven children and subluxation of the knee associated with genu valgus in three children (43%), which was bilateral in two (29%).

All of the children also showed signs of brain calcification. Scientists believe that Zika infection destroys brain cells and forms lesions, on which calcium is deposited.

Investigators have established a strong link between Zika virus infection during pregnancy and microcephaly in infants, but Dr. Jimmy Whitworth, a professor of international public health at the London School of Hygiene and Tropical Medicine, said the latest findings also reveal more of Zika’s harmful consequences.

“It is becoming increasingly clear that this virus can cause a wide range of other abnormalities, including visual and hearing defects and brain damage in babies with normal-sized heads,” he told Reuters.

The finding that the affected babies all had patterns of peripheral nerve damage, which had caused contracting of the joints, was “consistent with our knowledge that Zika virus is particularly damaging to nervous tissue,” he said.

The current Zika outbreak was first detected last year in Brazil, where it has been linked to more than 1,700 cases of microcephaly.

Sources: Reuters; August 9, 2016; and BMJ; August 9, 2016.

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