Symptoms and the 'Water Effect'

For individuals with Bothnian type palmoplantar keratoderma (PPKB), water is more than just a liquid—it is a powerful trigger for a unique set of symptoms. While the hallmark of the condition is thickened skin, the way that skin reacts to moisture is what truly sets PPKB apart from other types of skin thickening.

The ‘Hand-in-the-Bucket’ Sign

The most distinctive symptom of PPKB is aquagenic wrinkling ^[1]. This is often called the “hand-in-the-bucket” sign because of how quickly and dramatically the skin changes when it touches water.

Unlike the normal “pruning” that happens to anyone’s fingers after a long bath, people with PPKB experience this effect almost instantly—often within 2 to 5 minutes of contact ^[1][2]. During this reaction, the skin on the palms and soles undergoes several rapid changes:

• Swelling and Edema: The skin physically swells as water enters the cells ^[3].
• Maceration: The skin becomes soft, soggy, and wet-looking.
• Translucent White Papules: Small, clear-to-white bumps (papules) may appear and merge into larger thickened plates ^[4][2].
• Color Change: The skin often turns a distinctively opaque or “milky” white color.

Why Does Water Cause Pain?

For many, the “water effect” is not just a visual change; it is physically uncomfortable. When the skin swells rapidly, it can trigger several sensory symptoms ^[2][5]:

• Burning and Stinging: The rapid influx of water into the skin can cause a sharp burning sensation.
• Pruritus (Itching): A deep, intense itch is common during and after water exposure ^[2].
• Pain: In some cases, the swelling is severe enough to cause significant physical pain, making tasks like bathing or swimming difficult ^[2].

This reaction happens because of a genetic change in the AQP5 gene, which acts like a “gate” for water in your sweat glands. In PPKB, there are simply too many “gates” left open on the surface of your skin cells (a gain-of-function mutation), allowing water to flood into the skin cells much faster than it should ^[3].

Chronic Sweating (Hyperhidrosis)

Even when you are not in the water, your skin may feel constantly damp. This is due to hyperhidrosis, or excessive sweating ^[6]. In PPKB, the same genetic mutation that causes water to enter the skin also affects how the sweat glands function, leading to increased sweating even in cool temperatures or without physical activity ^[3].

This constant moisture can sometimes lead to secondary issues, such as a distinct odor or the development of tiny “pits” on the soles of the feet (pitted keratolysis), which occur when bacteria thrive in the moist, thickened skin.

When Do Symptoms Start?

PPKB is a congenital condition, meaning it is present from birth, though the signs may not be obvious immediately. Most parents notice the “water effect” during early infancy, often before the child is one year old ^[7]. A baby might cry or seem distressed during bath time because of the burning or itching sensations.

Tips for Parents: If you are bathing an infant or child with PPKB, consider applying a thick barrier ointment (like petroleum jelly) to their hands and feet before the bath to block water absorption. Keep bath times extremely brief, or rely on sponge baths for the rest of their body to prevent the distressing “water effect.”

As the child grows, the permanent thickening of the skin on the palms and soles (the keratoderma) becomes more apparent and stays consistent throughout their life ^[1].

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