Difference Between Plaque-Type and Pustular-Type Psoriasis and Their Risk of Ankylosing Spondylitis

Introduction

Psychological and physical health are deeply interconnected, and skin conditions like psoriasis can have significant implications for a person's overall health. Among the various types of psoriasis, plaque psoriasis and pustular psoriasis stand out due to their distinct characteristics and potential complications. This article delves into the differences between these two types of psoriasis and explores the relationship between psoriasis and ankylosing spondylitis, a chronic inflammatory disease that primarily targets the spine and sacroiliac joints.

Differences in Symptoms and Characteristics

Plaque-Type Psoriasis

Plaque psoriasis is a chronic, relapsing inflammatory skin disorder characterized by raised, thickened, and scaly patches. These plaques are typically found on the scalp, trunk, and limbs, but they can occur anywhere on the body. The epidermis in these areas exhibits abnormal reactive differentiation and hyperproliferation, making the skin plaques thick and easily recognisable. The plaques are well-defined, often with a silvery white scale, and they tend to be symmetrically distributed. One of the hallmark symptoms of plaque psoriasis is severe itching, which can significantly impact a person's quality of life.

Psoriatic arthritis, which affects about 10-20% of patients with psoriasis, can complicate the condition. It is characterized by inflammation of the joints, joint deformities, and a condition known as 'sausage digits' (dactylitis), where the entire digit becomes swollen and painful.

Pustular-Type Psoriasis

Pustular psoriasis is a rare form of psoriasis characterized by pustules or blisters covering swollen and red skin. These pustules are filled with fluid and are usually located on nonacral skin, meaning areas of the body not typically covered by skin folds, such as the chest, back, and arms. It is an immune-based condition that usually presents with a sudden onset of symptoms, including a rash and pustules, accompanied by systemic symptoms such as fever, pain, and general malaise. There are several subtypes of pustular psoriasis, including annular and circinate types and palmoplantar pustulosis. The circinate type tends to follow a subacute or chronic course, while palmoplantar pustulosis typically presents with chronic pustular eruptions on the palms and soles.

Complications of pustular psoriasis can be severe, including issues such as acute respiratory distress syndrome, secondary bacterial infections, hair loss, low blood albumin levels (hypoalbuminemia), low blood calcium levels (hypocalcemia), renal tubular necrosis, osteoarthritis, uveitis, cholangitis, liver damage, malabsorption, and malnutrition. However, there is no evidence to suggest that pustular psoriasis increases the risk of developing ankylosing spondylitis.

Risk of Ankylosing Spondylitis

While there is no known association between plaque-type psoriasis and ankylosing spondylitis, a strong correlation does exist between psoriatic arthritis and ankylosing spondylitis. Psoriatic arthritis can lead to joint deformities and inflammation, which can eventually contribute to the development of ankylosing spondylitis. On the other hand, there is no evidence of a direct link between pustular psoriasis and ankylosing spondylitis.

It is important to note that older patients with generalized pustular psoriasis have a poor prognosis. The acute form, known as erythrodermic pustular psoriasis, can lead to severe systemic complications, including sepsis, renal, hepatic, and cardiorespiratory failure. In such cases, sepsis is the most common cause of death.

Treatment Options and Management

Both plaque psoriasis and pustular psoriasis require careful and comprehensive management. Treatment options may include topical medications, phototherapy, and systemic therapies. For severe cases, newer drugs targeting tumor necrosis factor (TNF) alpha have shown promising results.

Anti-TNF alpha drugs, such as secukinumab, have demonstrated efficacy in treating psoriatic arthritis and ankylosing spondylitis. However, the effectiveness of these drugs can vary among different types of psoriasis and may require individualized treatment plans. Regular follow-ups and monitoring are essential to manage symptoms and monitor for potential complications.

Conclusion

The differences between plaque-type and pustular-type psoriasis, along with their respective risk factors, highlight the complexity of these skin conditions. While psoriasis does not directly increase the risk of ankylosing spondylitis, both conditions can benefit from the same class of drugs. Understanding the unique characteristics and potential complications of each type of psoriasis is crucial for effective management and improving the quality of life for those affected.