Osteopathia striata with cranial sclerosis (OSCS) causes the bones to become unusually hard and thick. The severity of the condition and the symptoms vary significantly from person to person, even within the same family. Features of the condition are generally present at birth. Symptoms may include skeletal abnormalities at the ends of long bones, hardening (sclerosis) of the bones of the head and face, large head size, and cleft palate. Some people with OSCS may also have developmental delay, hearing loss, heart defects, and breathing and feeding difficulties. Osteopathia striata cranial sclerosis is caused by variants in the AMER1 gene and is inherited in an X-linked dominant pattern. Diagnosis is based on the symptoms, clinical exam, and may be confirmed by the results of genetic testing.