Acral peeling skin syndrome (APSS) is a rare genetic skin disorder where the outermost layer of skin peels away painlessly, primarily on the hands and feet. It affects fewer than 1 in a million people worldwide and is present from birth or early childhood, though it can sometimes go undiagnosed for years because the peeling is painless and often mistaken for other conditions.
What Causes the Peeling
The skin on your hands and feet is built in layers. The outermost layer, called the stratum corneum, is essentially a shield of dead skin cells held together by a protein envelope. In APSS, a genetic mutation disrupts the glue that keeps this outer layer attached to the living cells beneath it.
Most cases trace back to mutations in the TGM5 gene, which provides instructions for making an enzyme called transglutaminase 5. This enzyme cross-links proteins to form a tough envelope around skin cells, keeping them bonded to one another. When the gene is mutated, the body either produces too little of this enzyme or none at all. Without it, the outer layer of skin separates from the layer just below (the stratum granulosum) and peels off with little resistance.
A smaller number of families carry mutations in a different gene, CSTA, which has been identified in only a handful of pedigrees so far. CSTA mutations cause a similar pattern of acral peeling, sometimes with features that overlap with a related condition called exfoliative ichthyosis.
Both genes follow an autosomal recessive inheritance pattern, meaning a child must inherit a defective copy from each parent to develop the condition. Parents who each carry one copy typically have no symptoms themselves.
How It Looks and Feels
The hallmark of APSS is superficial, painless peeling of the skin on the palms, fingers, soles, and toes. “Acral” simply means the extremities, and that’s where the peeling concentrates because those areas experience the most friction and moisture exposure throughout the day. The peeling tends to worsen in warm, humid conditions and after prolonged contact with water.
Unlike blistering disorders, APSS typically does not cause pain, scarring, or open wounds. The skin underneath the peeling area usually looks normal or slightly pink. Some people notice mild redness, and a skin biopsy may show subtle thickening of the outer skin layer (mild hyperkeratosis), but for most people the condition is cosmetically bothersome rather than physically painful. The peeling can be more noticeable during summer months or after activities that make the hands and feet sweat.
How It Differs From Similar Conditions
APSS is frequently confused with localized epidermolysis bullosa simplex (EBS), a condition that also causes skin problems on the palms and soles. The two can look strikingly similar, especially in young children. However, there are important differences in what triggers the skin damage and where it occurs at the microscopic level.
In EBS, blisters and erosions form in the deepest part of the epidermis, at the basal layer, and they’re typically triggered by mechanical trauma like rubbing, pressure, or friction. In APSS, the split happens much higher up, right at the junction between the outermost dead cell layer and the living cells beneath it. The trigger pattern is also different: APSS worsens with heat and humidity rather than with physical trauma. This distinction matters because it changes what a dermatologist looks for under the microscope and which genetic tests they order.
APSS can also overlap clinically with exfoliative ichthyosis, particularly in cases caused by CSTA mutations. The boundary between these two diagnoses is still being refined as more families are identified and genetically tested.
How It’s Diagnosed
Because APSS is so rare, diagnosis often takes time. A dermatologist will typically start with a clinical exam, noting the painless nature of the peeling and its restriction to the hands and feet. A skin biopsy can confirm the diagnosis by revealing a characteristic cleft between the stratum corneum and stratum granulosum, the exact location where the skin separates in APSS. This biopsy finding helps rule out conditions like EBS, where the split occurs deeper in the skin.
Molecular genetic testing provides the most definitive confirmation. Sequencing the TGM5 gene (and CSTA if TGM5 comes back normal) can identify the specific mutation responsible. This is especially useful for families considering genetic counseling, since identifying carrier status in parents helps clarify the risk for future children.
Managing APSS Day to Day
There is no cure for APSS, and because the condition results from a structural protein deficiency, the peeling cannot be fully prevented. Management focuses on protecting the skin and minimizing triggers. Keeping the hands and feet dry when possible, using emollients to maintain skin hydration without excess moisture, and avoiding prolonged exposure to heat and humidity can all reduce the frequency and severity of peeling episodes.
Because the peeling is painless and the underlying skin generally heals without scarring, many people with APSS manage the condition with relatively simple skin care routines. The biggest challenge for most is the cosmetic appearance, particularly during flares. For children, early diagnosis can spare families years of worry and unnecessary treatments aimed at conditions the child doesn’t actually have.