Introduction:
The incidence of complex and rare disorders worldwide is a major challenge in the healthcare field, as clinical features, diagnosis, and treatment should be evaluated as early as possible to avoid any major complications. One such rare disorder affecting humans is the SAPHO syndrome.
What Is SAPHO Syndrome?
SAPHO stands for synovitis, acne, pustulosis (pustular eruptions), hyperostosis (bone enlargement), and osteitis (inflammation of bone). This syndrome is intended to affect the skin, bones, and joints. Various genetic and environmental factors that include infectious agents may play a role in the incidence of this disorder. The most commonly associated infectious agent is Propionibacterium acnes. The presence of the HLA-B27 gene is also considered a risk factor for the incidence of SAPHO syndrome. This results in autoinflammation within the body that manifests in the musculoskeletal system. SAPHO syndrome causes generalized skeletal, arthritic, and dermatological disorders.
What Are the Dermatological Aspects of SAPHO Syndrome?
Clinical features on the skin are the most common manifestations of SAPHO syndrome. Common dermatological lesions associated with SAPHO syndrome are:
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Pustular Lesions on the Skin: This appears as a raised or elevated lesion with pus inside the lesion. This is a characteristic feature of SAPHO syndrome. Eighty percent of the people affected by SAPHO syndrome exhibit these pustular lesions on the skin. Such lesions are most common in the palmar and plantar regions of the body (palmar-plantar pustulosis - PPP). These sterile pustules develop over a long period and can be very painful. Recognizing these pustules is very important for diagnosing SAPHO syndrome. One hallmark feature of such pustules is their cracking nature with spontaneous healing. This is followed by the recurrence of the pustules in nearby areas.
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Acne: Acne or acneiform eruptions are a characteristic manifestation of SAPHO syndrome. Eruptive lesions like acne on regions like the face, trunk, palms, and feet are noticed. They are very painful and resistant to the regular treatment given for acne vulgaris. This is seen in about five percent of the population affected by SAPHO syndrome. The type of acne eruptions in SAPHO syndrome is generally the conglobata or fulminans type. These types are nodular and ulcerated in severe cases.
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Psoriasis and Arthritis: Some people with SAPHO syndrome experience plaques on the skin that appear scaly with red inflamed patches. This is accompanied by itching. In advanced cases, this is seen along with inflamed joints (psoriatic arthritis). The coexistence of psoriasis and musculoskeletal involvement can complicate the clinical picture but provide broad insight into the spectrum of SAPHO syndrome.
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Hidradenitis Suppurativa: This also occurs over a chronic period on the skin and is seen as painful abscesses and nodules in the armpits and groin. While not a direct component of SAPHO syndrome, there have been reported cases of concurrent occurrence, indicating a potential association between the two conditions. The presence of hidradenitis suppurativa alongside SAPHO syndrome introduces additional complexity to the clinical presentation, as patients may experience dermatological and musculoskeletal manifestations.
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Dissecting Cellulitis of Scalp (Perifolliculitis Capitis Abscedens et Suffodiens): This is a rare occurrence in SAPHO syndrome, where there is nodule formation within the scalp and causes hair loss.
What Are the Other Clinical Features (Musculoskeletal System)?
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Inflammation occurs in the synovial joint.
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The level of bone growth exceeds the normal (hyperostosis). This will cause physical deformities and result in restricted actions by the body (reduced mobility).
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There is inflammation and edema formation within the bones. This is seen most commonly with sternal and clavicle bones.
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The affected bone areas may show erythema as an external indicator of inflammation and overgrowth.
The time interval between the incidence of skin lesions and musculoskeletal manifestations is less than two years. Thus, any skin manifestations seen with arthritic changes should be evaluated for SAPHO syndrome.
How to Diagnose SAPHO Syndrome and Dermatological Aspects?
Differentiating a skin lesion from other causes and SAPHO syndrome is very important, as a proper treatment plan is necessary to ensure complete resolution without recurrence. To achieve this, evaluating the skin lesions and skeletal changes with clinical features, physical examination, and investigations (both laboratory and radiographic) is needed.
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Recognition of characteristic skin lesions, such as PPP, acneiform eruptions, and joint and bone involvement incidence, should raise suspicion for SAPHO syndrome. Additionally, a detailed patient history, including the presence of inflammatory musculoskeletal symptoms and family history, aids in narrowing down the diagnostic possibilities.
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Bone scans and X-rays can give an overview of the involvement of bone and joints. The periosteum and the cortex of the bone are thickened.
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In some cases, a skin biopsy may be performed to analyze the histopathological characteristics of skin lesions. While this may not be a diagnostic criterion on its own, it can give a clue about important information that, combined with clinical and radiological findings, supports the overall assessment of SAPHO syndrome.
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Since this is an inflammatory condition, obvious markers like erythrocyte sedimentation rate, IL-8, IL-18, C3, C4, and C-reactive protein levels are spiked.
How to Treat Dermatological Manifestations of SAPHO Syndrome?
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Non-steroidal anti-inflammatory drugs are first prescribed as the condition is heavily painful. This reduces the pain substantially.
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Sulfonamides are given to hinder bacterial action in the pustules and acne.
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Corticosteroid topical creams and phototherapy are advised for managing skin manifestations.
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In severe cases, retinoids are given. Isotretinoin is given for acne eruptions, and Acitretin is generally given for palmar plantar pustulosis.
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A short course of systemic corticosteroid treatment is also given in acute flare-ups of skin lesions.
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Disease-modifying anti-rheumatic drugs like Methotrexate are given when the condition is severe with the presence of rheumatic pain. The main objective is to modify the entire body's inflammatory process and slow down the progression of skin and musculoskeletal involvement.
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Biological therapy is instituted if there is an inadequate response to any of these therapies. This includes inhibitors of tumor necrosis factors like Etanercept or Adalimumab. They completely target the immune system and bring down the response.
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Any abscess that develops as a complication of skin lesions should be surgically managed by drainage after incision.
Conclusion:
SAPHO syndrome is a rare kind of disorder that presents with diagnostic challenges at every stage of clinical manifestation. The presence of pustular skin lesions, acneiform eruptions, and psoriatic features can serve as important diagnostic clues, guiding clinicians toward a comprehensive evaluation.
