Progressive macular hypomelanosis - Skin
PMH is characterized by numerous hypopigmented macules and patches that affect primarily the lumbar region and abdomen. Rarely, the condition extends to proximal limbs and neck. The hypopigmented macules are ill-defined, nummular, symmetric, and without scale. The lesions are asymptomatic without history of preceding infection, inflammation, or injury.
PMH may last for years, but typically it resolves before age 40. The condition affects chiefly adolescents and young adults, particularly women aged 13-38 years. PMH affects all populations worldwide, but it is more common in tropical regions and in patients with darker skin types.
The pathogenesis of PMH is unknown. However, recent studies suggest that the hypopigmentation may be due to Propionibacterium acnes. This bacterium is found in the sebum of the pilosebaceous duct within hypopigmented lesions. The precise mechanism by which P. acnes causes hypopigmentation is unclear, but it is hypothesized that the organism produces a substance that interferes with melanogenesis and/or melanosome distribution.
L81.9 – Disorder of pigmentation, unspecified
201284005 – Hypopigmentation disorder
- Pityriasis (tinea) versicolor presents as scaly hypo- or hyper-pigmented macules and patches with fungal elements seen on KOH.
- Pityriasis alba presents with hypopigmentation frequently located on the face with fine pityriasiform scaling.
- Post-inflammatory hypopigmentation presents in a patient with history of preceding dermatitis or other inflammatory dermatoses.
- Idiopathic guttate hypomelanosis presents as confetti-like macules on the extremities, particularly the forearms, calves, and shins.
- Vitiligo presents with sharply depigmented macules and patches commonly involving the face, genitalia, and extensor skin, or areas of trauma.
- Sarcoidosis generally presents as red-brown plaques with peripheral elevation and central hypopigmentation.
- Tuberculoid leprosy presents with anesthetic hypopigmented macules and patches that are most prominent on the face and extremities.
- Lepromatous leprosy can present with many widespread hypopigmented or slightly erythematous lesions. Lesions tend to be more prominent on the cooler parts of the body (eg, nose, earlobes, eyebrows, cheeks, ears, buttocks, and extensor and acral extremities).
- Leishmaniasis lesions (Old World and New World) may heal without therapy, leaving a hypopigmented, atrophic scar. Active lesions usually develop central ulceration. Microscopy or biopsy often reveals the presence of parasites.
- Secondary syphilis presents as a papulosquamous eruption involving the trunk and extremities, including the palms and soles. History of primary chancre should raise concern for this diagnosis, and most patients present with systemic symptoms such as fever, headache, sore throat, and malaise.
- Incontinentia pigmenti evolves from birth through childhood with hypopigmentation being the 4th (last) stage in the progression. Stages 1-3 represent a vesicular stage, verrucous stage, and hyperpigmented stage, respectively.
- Arsenic hypomelanosis (arsenical keratosis) presents as hyperpigmented macules and "rain-drop" hypomelanosis. A history of chronic arsenic exposure should be noted.
- Hypopigmented mycosis fungoides presents with hypopigmented scaly patches and plaques commonly located on the trunk, pelvic girdle, and lower limbs. Lesions are also associated with pruritus, poikiloderma, and ulceration.