Infantile cortical hyperostosis (ICH), also known as Caffey disease, was first reported by Roske in 1930 and described by Caffey and Silverman in 1945. ICH is a disorder affecting the skeletal system of infants.[1] ICH most commonly affects the mandible (70% to 90% of cases) and has the appearance of periosteal reaction. ICH is also known to affect the clavicle, rib, ulna, scapula, and rarely the ilia, parietal bones, and metatarsals. Usually unilateral when involving the scapula. Primary bone lesions are commonly asymmetric and localized to the diaphysis with sparing of the metaphysis and epiphysis. This pattern of involvement usually results in spindle-shaped bones. The disease usually spontaneously resolves within two years.[2]

Gensure et al. performed a genome-wide scan followed by fine mapping of individuals known to have the ICH's autosomal dominant form. Subsequently, genes were sequenced, and PCR amplification was performed. Gel electrophoresis confirmed that the affected individuals had a missense mutation in COL1A1 gene.[3]

ICH rarely occurs after the first year of age.[4] Radiographic findings include cortical thickening (hyperostosis) and subperiosteal new bone formation. There is a prenatal form of the disease called lethal prenatal cortical hyperostosis, which shows an autosomal recessive mode of inheritance and occurs before 35 weeks gestation. Polyhydramnios, angular deformities of the long bones, deformities of the ribs, prematurity, and lung disease are associated with this form. The infantile (classical) form that appears after 35 weeks of gestation is less severe and more common.[2] Ultrasound in utero can show changes such as bone curvature and cortex deformities consistent with ICH.[4]

ICH's familial form is autosomal dominant with variable penetrance and classically associated with a COL1A1 point gene mutation (3040C to T) on chromosome 17q21.[5] This missense mutation results in an arginine to cysteine substitution (R836C) in the triple helix of the alpha-1 chain of type 1 collagen. Type 1 collagen is essential for bone mineralization and makes up about 9% of the bone matrix. These fibers are composed of one a2 and two a1 procollagen chains followed by cleavage of the N and C termini by proteinases. Collagens provide strength and interact with proteins to form the extracellular matrix necessary for cell function.[6]

The relation between this missense mutation and the skeletal findings of ICH are unknown. Still, proposed mechanisms include an inability of chromosome interactions with proteins (IL-2), defective cross-linking between the bone and abnormal collagen, and decreased thermal stability of collagen.[6] The average age of presentation of ICH's familial form is between 6 to 8 weeks, and it commonly involves the tibias. Twenty-four percent of infants present at birth with the familial form. ICH's sporadic form usually involves the mandible with an average age of onset between 9 and 11 weeks. Some sporadic cases result from prolonged administration of prostaglandins E1 and E2 in infants with cyanotic heart disease.[4]

COL1A1 and COL1A2 gene mutations cause subtypes of Ehlers-Danlos syndrome and osteogenesis imperfecta. Gly substitutions in the triple helix lead to defective type I collagen resulting in fractures and findings consistent with osteogenesis imperfecta types II-IV. Some individuals with ICH have features seen in Ehlers-Danlos, such as hyperextensible skin, joint hyperlaxity, and inguinal hernias.[6]

Histologic findings in the early stages of the disease are limited to the periosteum. Gradually the periosteum’s fibrous layer breaks down and becomes associated with muscles, tendons, and fascia. Osteoid trabeculae enter the muscles, soft tissue, and connective tissue, forming new bone and resulting in increased diameter. Eventually, the periosteum reforms a fibrous layer over the new bone, and the extra bone is removed.[4]