Diagnosis Code B35.1, recognized within the International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM), specifically designates tinea unguium, more commonly known as onychomycosis. This code is crucial for medical billing and statistical tracking, providing a standardized way to classify and document this prevalent fungal infection of the nails. Effective since October 1, 2015, and updated annually, B35.1 is a billable, specific code used within the American ICD-10-CM system. It’s important to note that international versions of ICD-10 B35.1 might have variations.
What is Diagnosis Code B35.1?
B35.1 is the ICD-10-CM code specifically assigned to tinea unguium, a fungal infection affecting the nails. This condition is a type of dermatophytosis, caused primarily by dermatophytes, yeasts, and nondermatophyte molds. The code falls under the broader category of B35, which encompasses all dermatophytoses, but B35.1 narrows the diagnosis down to infections specifically located in the nails. Understanding this specificity is important for accurate medical coding and claim processing.
Applicable Conditions for B35.1
The application of diagnosis code B35.1 is not limited to just tinea unguium. It is also applicable and appropriate for coding the following related conditions:
- Dermatophytic onychia: This term directly refers to nail infections caused by dermatophytes, the most common group of fungi responsible for onychomycosis.
- Dermatophytosis of nail: A broader term encompassing any dermatophyte infection localized to the nail structure.
- Onychomycosis: This is the medical term most frequently used to describe fungal nail infections, and it is directly represented by code B35.1.
- Ringworm of nails: While “ringworm” is a common term for dermatophyte infections, including onychomycosis, its use in medical settings is less frequent than onychomycosis. However, for coding purposes, ringworm of the nails aligns with B35.1.
Synonyms for B35.1
To further clarify the scope of B35.1, several synonyms are used interchangeably with tinea unguium and onychomycosis in clinical practice:
- Onychomycosis (nail fungal infection): This is a straightforward and patient-friendly way to describe the condition that B35.1 codes for.
- Onychomycosis/dystrophy: This term highlights that onychomycosis often leads to nail dystrophy, which includes changes in nail appearance, thickness, and texture.
- Total dystrophic onychomycosis: This refers to a severe form of onychomycosis where the entire nail unit is affected and significantly deformed due to the fungal infection.
Clinical Significance of B35.1
Clinically, onychomycosis, coded as B35.1, represents a common nail disorder. These infections can be caused by various types of fungi, including dermatophytes like Trichophyton rubrum and Trichophyton mentagrophytes, yeasts such as Candida, and nondermatophyte molds. The infection often manifests with changes in nail color (yellowish or whitish discoloration), thickening, brittleness, and separation from the nail bed. Diagnosis typically involves clinical examination and laboratory confirmation, such as microscopic examination of nail scrapings or fungal culture. Accurate diagnosis coding with B35.1 is essential for appropriate billing for diagnostic procedures and subsequent treatments, which can range from topical antifungal medications to oral antifungal therapies in more severe or recalcitrant cases.
B35.1 Code History and Updates
The diagnosis code B35.1 has been consistently recognized in the ICD-10-CM system since its inception in 2016. It was introduced as a new code in the 2016 ICD-10-CM release, effective from October 1, 2015, marking the first year of the non-draft ICD-10-CM implementation. Since then, through the 2025 edition effective October 1, 2024, B35.1 has remained unchanged. This stability indicates the established and ongoing relevance of this code for classifying and tracking tinea unguium in medical records and healthcare statistics.
In conclusion, diagnosis code B35.1 is a vital tool in medical coding for accurately representing tinea unguium or onychomycosis. Its specific nature allows for precise documentation, billing, and epidemiological tracking of this common fungal nail infection within the healthcare system.
