Hope and Blessing Mofokeng have craniosynostosis, or the premature closure of the cranial sutures.
Even more unusual is that both suffer from the rare congenital condition.
Hope underwent six hours of surgery on Tuesday and is recovering well.
Blessing was due to undergo surgery at the same time but it was postponed as she fell ill.
She will be operated on within the next few weeks.
The Smile Foundation is facilitating the life-changing operations with an expert surgical team at Tygerberg, sponsored by the Clicks Helping Hand Trust.
Smile Foundation operations executive director Moira Gerszt said: “This is a unique situation. We have never had identical twins who suffer from the same condition and both require surgery.”
She said the exceptional surgical team at Tygerberg, led by Dr Frank Graewe and Dr Alexander Zuhlke, is confident it can successfully correct the deformities.
“Cranio surgeries are not offered by the surgeons in every unit at academic hospitals in South Africa.
“These types of craniofacial surgeries need a dedicated plastic and reconstructive surgeon who is familiar with performing such procedures on paediatric patients.
“We are so grateful to the team at Tygerberg, who together with the National Department of Health have offered to undertake these two surgeries in collaboration with the Department of Plastic and Reconstructive Surgery at Universitas Academic Hospital in Bloemfontein,” Gerszt added. Graewe said: “Both patients suffer from sagittal suture synostosis.
“Sagittal suture synostosis and the resulting scaphocephaly lead to the typical skull deformity with a bossing forehead and a long and narrow skull.
“It leads to a cosmetic deformity and pressure on the developing brain can lead to clinical symptoms, such as chronic headaches.
“We will do a total cranial vault decompression and craniofacial remodelling for them, with the hope of giving them both a better future.”
Hope was cradled by her dad Siphiwe Maunga, who said: “Everything went well.
“We were just scared when (Blessing) couldn’t go for her operation because they never knew if it was a flu and she may have had an infection on the lungs, but it was not. They ran tests and she is okay.
“Hope is coping, the pain comes and goes and they are giving her medication for that.
“We haven’t been able to sleep. But we are thankful.”
He said the twins’ personalities were poles apart, but the two had a strong attachment.
Blessing was hyperactive, as she waved at the passers-by at hospital, while Hope was more subdued, Maunga said.