Clinical Characteristics of Multiple Café-Au-Lait Macules and Their Potential Significance in the Early Screening of Genetic Diseases

Introduction

Café-au-lait macules (CALMs) are common pigmented skin lesions characterized by smooth, well-demarcated macules ranging from light brown to dark brown.^1,2 While generally benign, they can serve as markers for potential genetic disorders, particularly neurocutaneous syndromes such as neurofibromatosis type 1 (NF1).^3,4 NF1 is an autosomal dominant genetic disorder caused by mutations in the NF1 gene and is one of the most well-documented diseases associated with CALMs.⁵ Early identification of patients at risk of genetic disorders based on CALM characteristics can significantly improve disease management and prognosis, particularly in preventing complications such as skeletal deformities and central nervous system (CNS) abnormalities.⁶

The diagnostic significance of CALMs in NF1 has been extensively studied. One of the diagnostic criteria for NF1 is the presence of six or more CALMs, with each macule exceeding 0.5 cm in diameter in prepubertal individuals or ≥ 1.5 cm in adults.⁷ Studies have shown that the number and distribution of CALMs are associated with the severity of NF1-related complications, including neurofibromas, skeletal abnormalities, and learning disabilities.^8,9 Furthermore, CALMs located on the face and neck are more likely to be associated with CNS manifestations, such as optic pathway gliomas and hydrocephalus.^10,11 While NF1 is the most common genetic disorder associated with CALMs, other syndromes, such as McCune-Albright syndrome, Legius syndrome, and tuberous sclerosis complex, may also present with similar skin manifestations.^10,12 Differentiating these conditions is crucial due to their varying systemic involvement and prognoses. Additionally, sporadic CALMs occur in the absence of genetic susceptibility, typically as isolated lesions without systemic associations.^13,14

Given the potential clinical significance of CALMs, incorporating their characteristics into early genetic disease screening programs can improve diagnostic accuracy. Studies suggest that CALM features, particularly their number and distribution, can serve as non-invasive screening markers for identifying patients at risk of genetic syndromes.^13,15 Imaging techniques such as MRI further elucidate the relationship between CALMs and systemic abnormalities, with manifestations like neurofibromas and skeletal deformities being common in patients with extensive CALMs.¹⁶

Although the link between CALMs and genetic disorders has been established, systematic analyses of CALM clinical features across different patient populations remain limited. Moreover, the predictive value of CALM distribution and size in identifying systemic abnormalities has not been fully explored. This study follows a retrospective design, analyzing data from patients diagnosed between May 2021 and May 2024 in two hospitals. The retrospective design allows us to utilize existing patient records to explore the relationship between CALM characteristics and associated systemic symptoms, without the need for new data collection or interventions. This approach efficiently identifies patterns and trends that can inform genetic disease screening, particularly for genetic disorders such as NF1.

This study aims to evaluate the clinical and pathological characteristics of CALMs in patients with or without associated skin manifestations, with a focus on their significance in early screening for genetic diseases. By employing detailed clinical evaluations and imaging studies, this research seeks to enhance the understanding of CALMs as early screening markers for genetic diseases, particularly NF1, and to lay the groundwork for future diagnostic guidelines.

Methods

Study Design and Population

This study is a retrospective analysis conducted from May 2021 to May 2024. The cases were sourced from the Department of Dermatology at the Seventh Medical Center of Chinese PLA General Hospital and Longgang Central Hospital. A total of 98 patients were included in the study, which was approved by the ethics committees of the Seventh Medical Center of Chinese PLA General Hospital and Longgang Central Hospital. This study was conducted in accordance with the Declaration of Helsinki. All subjects signed the consent form before participation in the study. Consent form was obtained from the legal guardians of all underage participants prior to their involvement in the study. The ages of all patients ranged from 8 to 60 years, and they all provided complete medical histories and imaging data. The inclusion criteria involved patients with multiple CALMs (≥ 6) or isolated CALMs (< 6). Exclusion criteria included incomplete data, insufficient follow-up, patients with other inflammatory or secondary skin diseases, and those with serious systemic diseases that could potentially affect the study results. Based on the number of CALMs and associated manifestations, the study population was divided into three groups: Group 1 (n = 39) had multiple CALMs (≥ 6), with other skin manifestations (such as freckles, skin fibromas, etc).; Group 2 (n = 32) had multiple CALMs (≥ 6) but without other skin manifestations; and Group 3 (n = 27) had isolated CALMs (< 6), with no clear etiology. This study ensured the representativeness of the study subjects and data integrity through strict inclusion and exclusion criteria.

Clinical Evaluation

All study participants will undergo a detailed clinical evaluation. First, the physician will conduct a physical examination of the patients’ CALMs, recording their number, distribution, color, and other characteristics. To measure the size of each CALM, a caliper will be used to determine its longest diameter in millimeters. The color of CALMs will be assessed visually and categorized as light brown and dark brown. A standardized color scale will be referenced to reduce subjective differences in color interpretation. The presence of other skin manifestations such as freckles, skin fibromas, skin folds, and pigment loss will also be evaluated. Additionally, the physician will assess whether the patients have any systemic symptoms, particularly related to the nervous and skeletal systems (such as neurofibromas, skeletal deformities, etc). For patients with a family history of genetic diseases, the presence of hereditary conditions such as neurofibromatosis and xeroderma pigmentosum will be documented.

Imaging Examination

All patients will undergo a full-body MRI scan to assess abnormalities in the nervous and skeletal systems. The neurological examination will include brain scans, focusing on lesions such as neurofibromas and hydrocephalus. The skeletal system examination will cover the spine, limbs, and long bones, primarily looking for skeletal deformities and bone fibromas. The scanning will use multi-planar sequences (such as T1, T2-weighted imaging) combined with contrast-enhanced scans to improve lesion visibility. Experienced radiologists in accordance with standardized criteria will interpret all imaging results.

Statistical Analysis

All data analyses were performed using SPSS 25.0 software. Continuous variables were expressed as mean ± standard deviation (SD), and inter-group differences were analyzed using independent sample t-tests or Mann–Whitney U-tests. Categorical variables were described by frequency and composition ratios, and inter-group comparisons were conducted using chi-square tests or Fisher’s exact tests. Additionally, logistic regression analysis was used to calculate odds ratios (OR) and their 95% confidence intervals (95% CI) to explore the relationship between the number, size, and distribution of CALMs and systemic symptoms, and to evaluate the clinical significance of the screening model. All tests were two-tailed, and a p-value < 0.05 was considered statistically significant.

Results

Clinical and Pathological Characteristics of Patients

This study included 98 patients, and Table 1 summarizes the clinical and pathological characteristics of the three groups. Group 1 (n = 39) had an average age of 25.8 ± 8.2 years, with a higher rate of positive family history (31%). In terms of ethnicity, Group 1 had a majority of Han (94.87%) and a minority of Minority (5.13%). Regarding region, Group 1 had 23 patients from urban areas and 16 from rural areas. Among these patients, 64% had ≥ 10 CALMs, and most had dark brown spots (72%) and large areas (> 15 cm², 38%). Group 2 (n = 32) had an average age of 24.3 ± 7.5 years, with a family history rate of 19%. Among these patients, 50% had ≥ 10 CALMs and 50% had between 6 and 10 spots, with most spots being dark brown (63%). Group 3 (n = 27) had the youngest average age (21.5 ± 6.9 years), and light brown CALMs (70%) predominated. All patients in this group had fewer than 6 spots. In groups 1 and 2, CALMs were primarily located on the face and neck, while in group 3, they were more frequently found on the limbs. Overall, patients in group 1 exhibited stronger features of genetic disease, particularly in terms of the number, color, and associated symptoms of CALMs, highlighting their significance as clinical indicators for early genetic disease screening.

Table 1 Basic Characteristics of Patients

Analysis of Clinical Manifestations and Imaging Examination Results

Table 2 and Figure 1 show the incidence of neurological and skeletal system symptoms in different groups. Group 1 had a significantly higher incidence of neurological and skeletal system symptoms compared to group 2 and group 3. Specifically, the incidence of neurofibromas in group 1 was 38%, much higher than 25% in group 2 and 4% in group 3 (P = 0.005). Additionally, group 1 exhibited higher incidences of hydrocephalus (13%) and intellectual disability (10%), while group 2 and group 3 had relatively lower rates with no significant differences (P = 0.166, P = 0.580). In terms of skeletal symptoms, the incidence of bone deformities (38%) and osteofibromas (21%) in group 1 was also significantly higher than in Group 2 (25%, 13%) and group 3 (0%) (P = 0.001, P = 0.044). Imaging results (Table 3 and Figure 2) further supported these clinical findings. Group 1 had an imaging abnormality rate of 90%, indicating that most patients had abnormalities in the neurological or skeletal systems, whereas the abnormality rates in group 2 and group 3 were 31% and 7%, respectively (P < 0.001). These data suggest that patients in group 1 are more likely to have neurological and skeletal abnormalities related to genetic diseases, especially symptoms like neurofibromas, hydrocephalus, and osteofibromas, which are consistent with the features of diseases such as Neurofibromatosis Type 1 (NF1). In contrast, imaging abnormalities were less common in Groups 2 and 3, indicating that these patients may have milder symptoms or not exhibit clear genetic disease features. The underlying causes of these differences, including the potential interaction between genetic and environmental factors, warrant further investigation to fully understand their contribution to these disparities. In summary, these findings underscore the clinical significance of CALMs in identifying patients at risk for genetic disorders, particularly those with neurological and skeletal abnormalities, and highlight the importance of using CALMs as an early diagnostic tool in genetic disease screening.

Table 2 The Incidence of Neurological and Skeletal System Symptoms in Different Groups

Table 3 The Imaging Findings of Different Groups

Figure 1 Incidence of neurological symptoms (A) and skeletal symptoms (B) in patients from different groups. *p < 0.05, **p < 0.01, compared to group 1.

Figure 2 The imaging findings of different groups. **p < 0.01, compared to group 1.

The Association Analysis Between CALMs Characteristics and Symptoms Related to Genetic Diseases

Figure 3 presents the results of a multivariate logistic regression analysis examining the relationship between the number, size, distribution of CALMs, and other clinical characteristics with neurological and skeletal system symptoms. According to the results, the number of CALMs (especially ≥10) was significantly associated with the occurrence of neurological symptoms, with an odds ratio (OR) of 7.664 (95% CI: 2.257–26.020, P = 0.001), indicating that patients with ≥10 CALMs had a higher risk of developing neurological symptoms. Similarly, the number of CALMs (≥10) was also significantly associated with the occurrence of skeletal system symptoms, with an OR of 4.623 (95% CI: 1.264–15.672, P = 0.014). Additionally, the distribution of CALMs (especially on the face and neck) had some influence on the relationship with neurological and skeletal system symptoms, although some variables showed slightly higher P-values, suggesting a possible impact on symptom occurrence. In summary, these findings support the importance of CALM quantity and distribution in predicting neurological and skeletal symptoms, making them crucial markers for early genetic disease screening, particularly in identifying systemic abnormalities.

Figure 3 Multivariate logistic regression analysis of CALMs characteristics and genetic disease-related symptoms. (A) Multivariate logistic regression analysis for the association between CALMs characteristics and neurological symptoms, showing odds ratio (OR) with 95% confidence intervals (CIs) and corresponding p-values. (B) Receiver operating characteristic (ROC) curves illustrating the diagnostic performance for neurological symptoms, with area under the curve (AUC) values displayed for each parameter. (C) Multivariate logistic regression analysis for skeletal system symptoms, displaying OR, 95% CIs, and p-values. (D) ROC analysis evaluating the diagnostic performance for skeletal system symptoms, with AUC values for each characteristic or factor. The results suggest that specific CALMs characteristics are associated with neurological and skeletal symptoms, demonstrating moderate diagnostic accuracy.

Discussion

CALMs are benign pigmented skin lesions increasingly recognized as potential biomarkers for genetic diseases, particularly neurocutaneous syndromes such as NF1.^17,18 This study underscores the importance of CALM characteristics (eg, number, size, and distribution) as clinical indicators in the early screening of genetic disorders. Our findings highlight the significant associations between CALM features and systemic abnormalities, particularly in the nervous and skeletal systems, reinforcing their diagnostic utility.

The data revealed that group 1 patients exhibited significantly higher rates of neurological and skeletal abnormalities compared to groups 2 and 3. Neurological manifestations in group 1, including neurofibromas (54%) and hydrocephalus (13%), align with NF1 diagnostic criteria and corroborate prior research emphasizing the diagnostic value of CALMs in NF1 screening. This is consistent with previous studies, which also highlight the importance of CALM features, such as quantity and distribution, in early NF1 diagnosis. However, while those studies focused on the general correlation between CALMs and systemic symptoms, our research specifically emphasizes the predictive value of having ≥ 10 CALMs as a reliable indicator of neurological and skeletal abnormalities. This distinction provides additional insights into the use of CALMs as a diagnostic tool in genetic disease screening.^19,20 Additionally, skeletal abnormalities such as deformities (38%) and osteofibromas (21%) further substantiate the strong correlation between CALM characteristics and the pathophysiology of genetic disorders. Our results also indicate that CALM quantity (≥ 10) is a reliable predictor of neurological and skeletal symptoms, with OR of 7.664 and 4.623, respectively. For example, earlier researches have found correlations between CALMs and neurofibromas, but our study uniquely emphasizes the predictive value of CALM quantity in forecasting systemic abnormalities, offering a refined diagnostic approach. Moreover, the anatomical distribution of CALMs, particularly on the face and neck, was linked to an increased risk of central nervous system (CNS) abnormalities, such as optic gliomas and brainstem lesions. Although certain variables exhibited limited statistical significance, these observations underscore the importance of comprehensive clinical evaluations and imaging for patients with extensive CALMs.

Interestingly, compared to group 1, group 2 showed a lower prevalence of systemic abnormalities. This distinction highlights the additional diagnostic value of accompanying skin findings, such as freckles and cutaneous neurofibromas, which are hallmark features of NF1. Conversely, group 3, characterized by isolated or few CALMs, exhibited minimal systemic involvement, suggesting that isolated CALMs are more likely sporadic and benign.²¹ Imaging played a crucial role in identifying systemic abnormalities, with MRI revealing a 90% abnormality rate in group 1 patients. This supports integrating imaging techniques into the early diagnostic workflow for patients with extensive CALMs, particularly in the presence of additional risk factors. Furthermore, advanced imaging modalities, such as contrast-enhanced MRI can enhance the detection of subtle lesions and help differentiate NF1 from other genetic syndromes, such as Legius syndrome and McCune-Albright syndrome.²²

Despite its strengths, this study has certain limitations. First, the absence of genetic screening might have led to misdiagnoses or missed diagnoses in some cases. Since genetic mutations, particularly in the NF1 gene, are established diagnostic markers, future studies incorporating genetic testing could validate and improve the accuracy of screening models.^21,23 Additionally, the retrospective design and relatively small sample size may limit the generalizability of the findings. Prospective studies with larger cohorts and standardized protocols could further elucidate the associations observed in this study.

In conclusion, this study reinforces the clinical significance of CALM characteristics in the early screening of genetic diseases. By leveraging CALM features, along with detailed clinical evaluations and imaging findings, clinicians can improve the early detection and management of conditions such as NF1. Integrating genetic testing into future research and clinical protocols could further optimize diagnostic accuracy and patient outcomes.

Conclusion

This study highlights the clinical significance of CALMs as markers for early genetic disease screening, particularly for NF1. The findings demonstrate that CALM quantity (≥ 10), distribution, and associated skin features are closely linked to systemic abnormalities in the nervous and skeletal systems. Incorporating CALM evaluation into early diagnostic protocols, supplemented with imaging technologies, holds promise for improving the early detection and management of genetic diseases.