SAPHO Syndrome
SAPHO syndrome is a chronic rheumatologic disorder that involves the skin, bone, and joints. The name SAPHO is an acronym for the primary manifestations associated with this disorder: synovitis, acne, pustulosis, hyperostosis, and osteitis. It is listed b
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SAPHO Syndrome Caroline L. LaRosa and Andrea L. Zaenglein
24.1
Introduction
SAPHO syndrome is a chronic rheumatologic disorder that involves the skin, bone, and joints. The name SAPHO is an acronym for the primary manifestations associated with this disorder: synovitis, acne, pustulosis, hyperostosis, and osteitis. It is listed by the National Institutes of Health as a rare disease, but it is an important one for physicians to include in their differential diagnosis for acne as it is often misdiagnosed and under-recognized.
24.2
Background
As a result of the lack of awareness and difficulty in diagnosing SAPHO syndrome, it may be unrecognized or misdiagnosed, and therefore, the exact prevalence is unknown [1, 2]. SAPHO typically affects children and young to middle-aged adults [3]. There is no sexual predilection. Familial cases have been reported but are rare. The etiology of SAPHO syndrome is still largely unknown, but it is likely the result of a complex interaction between various genetic and immunologic factors. Inflammation, particularly abnormal neutrophil function and response, affects the skin and bones. Genetic predisposition plays a prominent role in patients with SAPHO syndrome. Certain genes have been suspected as having a role in SAPHO due to their association with other inflammatory disorders. These candidate genes include the proline-serine-threonine phosphatase-interacting protein 2 gene (PSTPIP2), which
C.L. LaRosa, B.S. • A.L. Zaenglein, M.D. (*) Department of Dermatology and Pediatrics, Penn State/Milton S. Hershey Medical Center, 500 University Drive, Hershey, PA 17033, USA
J.A. Zeichner (ed.), Acneiform Eruptions in Dermatology: A Differential Diagnosis, DOI 10.1007/978-1-4614-8344-1_24, © Springer Science+Business Media New York 2014
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encodes a protein expressed on macrophages and is involved in macrophage motility. In addition, the LPIN2 gene may be involved, as it encodes a protein involved in lipid metabolism and inflammation [4]. Mutations of the LPIN2 gene also play a role in Majeed syndrome, which shares the SAPHO feature of chronic recurrent multifocal osteomyelitis. Finally, the NOD2 gene is also a candidate, as it is involved in the development of bacterial recognition and inflammation. NOD2 is also strongly associated with Crohn’s disease. While no variants in any of these genes have been found consistently in SAPHO patients, two rare variants of LPIN2 have been associated in SAPHO patients with psoriasis. The LPIN2 locus is weakly associated with the psoriasis susceptibility locus, PSORS10, and therefore may account for the psoriasis component of SAPHO in some patients. While there is similarity between psoriasis and SAPHO, affected individuals do not show a predominance of class II HLA genes (HLA-B27, HLA-Cw6, or HLA-DR) typical for psoriasis [3]. Evidence for the genetic basis of a SAPHO-like phenotype was found in the observance of neutrophil defects in patients with SAPHO [5]. A significant reduction in oxidant production in ne
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