Granular parakeratosis (GP) is a rare, benign skin condition characterized by reddish-brown or brown scaly papules that often merge into thicker plaques. While it was first described in the axilla region, it can also affect other intertriginous areas such as the groin, submammary folds, the abdomen, or the lumbosacral region.
Who Is Affected by Granular Parakeratosis?
Although GP is uncommon, it has been reported in people of all ages — including children, adults, men, and women. Epidemiological observations suggest that middle-aged and older women may be more frequently affected. The prevalence in women is hypothesized to be linked to the higher frequency of cosmetic product application in the underarm area, such as deodorants and antiperspirants, combined with shaving practices that may compromise the skin barrier.
Why Does Granular Parakeratosis Happen?
The cause of GP remains uncertain, but several hypotheses exist. One influential theory focuses on a defect in filaggrin processing. Filaggrin is crucial for skin barrier formation. In GP, the conversion of profilaggrin to filaggrin may be impaired, causing keratohyalin granules to accumulate instead of breaking down normally.
External mechanical and chemical factors also appear to contribute. Friction, heat, sweating, and occlusion have been frequently associated with GP. Chemical irritants are particularly important. Among them, benzalkonium chloride, a common detergent and disinfectant ingredient, has been repeatedly linked to GP in case reports.
It is important to note that granular parakeratosis is not caused by a pathogen. It is not a fungal, bacterial, or viral infection, despite often resembling tinea corporis or candidiasis. And due to these observations, many experts believe GP represents a reactive epidermal response to physical or chemical stress rather than a primary skin disorder.
What Are the Clinical Symptoms of Granular Parakeratosis?
GP typically presents as red or brown scaly papules or plaques in skin-fold regions. Some individuals experience itching or irritation, though many remain symptom-free. In certain cases, the affected skin may peel as it heals.
Clinical duration varies widely. GP may resolve in a matter of weeks, especially in children, but in some adults the condition can persist for many years. Isolated reports describe lesions lasting decades.
How Is Granular Parakeratosis Diagnosed?
Diagnosis is primarily based on clinical suspicion and confirmed via histopathological examination. Because granular parakeratosis mimics common conditions like inverse psoriasis, contact dermatitis, and erythrasma, visual inspection alone is often insufficient for a definitive diagnosis.
Dermoscopy involves using a handheld device with high-quality magnification and lighting to examine skin structures invisible to the naked eye. Under a dermoscope, granular parakeratosis often reveals white scales, brownish structureless areas, and a lack of specific vascular patterns associated with psoriasis. High-precision optical equipment is essential here; utilizing devices such as the IBOOLO dermatoscope like DE-4100 PRO allows dermatologists to observe the fine scaling patterns and lack of fungal elements that help distinguish this condition from superficial fungal infections before invasive procedures are performed.
The gold standard for diagnosis is a skin biopsy. The pathology shows compact parakeratosis and retained keratohyalin granules, which are considered hallmark features.
Is Granular Parakeratosis Dangerous?
Granular parakeratosis is a benign condition. It is not premalignant, meaning it does not lead to skin cancer, and it does not cause systemic illness or internal organ damage. The primary burden of the disease is the impact on the patient's quality of life due to cosmetic disfigurement and pruritus.
However, the chronicity of the condition can lead to secondary complications. Constant scratching due to itching can break the skin barrier, leading to secondary bacterial superinfection (such as Staphylococcus aureus). Furthermore, misdiagnosis often leads to the inappropriate long-term use of potent topical steroids or antifungal agents, which can cause skin atrophy or contact sensitization, complicating the clinical picture.
How Is Granular Parakeratosis Treated?
There is no single standard of care for granular parakeratosis, but treatment strategies focus on removing the precipitating factors and reducing inflammation. Management typically proceeds in a stepwise fashion.
•Removal of Irritants
The most critical step is identifying and eliminating the causative agent. Patients are advised to stop using all deodorants, antiperspirants, and perfumed body washes in the affected area. If an antiseptic laundry rinse is being used, it must be discontinued, and clothes should be re-washed to remove chemical residues like benzalkonium chloride. In infants, discontinuation of zinc oxide pastes often leads to resolution.
• Topical Therapies
(1) Corticosteroids: Low-to-medium potency topical steroids are frequently used to reduce inflammation and itching.
(2) Vitamin D Analogs: Calcipotriene cream has shown efficacy in normalizing keratinization. By promoting proper cell differentiation, it helps correct the defect in the stratum corneum.
(3) Keratolytics: Agents such as ammonium lactate or urea help break down the thickened skin and assist in shedding the retained granules.