Some patients develop a rheumatoid factor-positive polyarthritis. Survivors can also develop fish-like scales and retention of a waxy, yellowish material in seborrheic areas, with ear adhered to the scalp.The oldest known survivor is Nusrit "Nelly" Shaheen, who was born in 1984 and is in relatively good health as of June 2021. The maximum lifespan of patients with this disease has not yet been determined with the new treatments.A study published in 2011 in the Archives of Dermatology concluded: "Harlequin ichthyosis should be regarded as a severe chronic disease that is not invariably fatal. With improved neonatal care and probably the early introduction of oral retinoids, the number of survivors is increasing." Epidemiology
The condition occurs in roughly 1 in 300,000 people. As an autosomal recessive condition, rates are higher among certain ethnic populations with a higher likelihood of consanguinity. History
The disease has been known since 1750, and was first described in the diary of Rev. Oliver Hart from Charleston, South Carolina:

"On Thursday, April the 5th, 1750, I went to see a most deplorable object of a child, born the night before of one Mary Evans in Chastown. It was surprising to all who beheld it, and I scarcely know how to describe it. The skin was dry and hard and seemed to be cracked in many places, somewhat resembling the scales of a fish. The mouth was large and round and open. It had no external nose, but two holes where the nose should have been.
Harlequin-type ichthyosis is a genetic disorder that results in thickened skin over nearly the entire body at birth. The skin forms large, diamond/trapezoid/rectangle-shaped plates that are separated by deep cracks. These affect the shape of the eyelids, nose, mouth, and ears and limit movement of the arms and legs. Restricted movement of the chest can lead to breathing difficulties. These plates fall off over several weeks. Other complications can include premature birth, infection, problems with body temperature, and dehydration. The condition is the most severe form of ichthyosis, a group of genetic disorders characterised by scaly skin.Harlequin-type ichthyosis is caused by mutations in the ABCA12 gene. This gene codes for a protein necessary for transporting lipids out of cells in the outermost layer of skin. The disorder is autosomal recessive and inherited from parents who are carriers. Diagnosis is often based on appearance at birth and confirmed by genetic testing. Before birth, amniocentesis or ultrasound may support the diagnosis.There is no cure for the condition. Early in life, constant supportive care is typically required. Treatments may include moisturizing cream, antibiotics, etretinate or retinoids. Around half of those affected die within the first few months; however, retinoid treatment can increase chances of survival. Children who survive the first year of life often have long-term problems such as red skin, joint contractures and delayed growth. The condition affects around 1 in 300,000 births. It was first documented in a diary entry by Reverend Oliver Hart in America in 1750.